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Chemical, structural and electronic properties of graphite fluorosulfate derivatives Karunanithy, Somasundaram 1984

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C. • 5 CHEMICAL, STRUCTURAL AND ELECTRONIC PROPERTIES OF GRAPHITE FLUOROSULFATE DERIVATIVES by SOMASUNDARAM KARUNANITHY B.Sc. (Hons.), U n i v e r s i t y of S r i Lanka, Peradeniya, 1977 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILISOPHY i n THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA May, 19 8 4 ^ Somasundaram Karunanithy In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It i s understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of CHEMISTRY The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 JUNE 1 1 , 1984. Date ABSTRACT Emphasis i s p l a c e d i n t h i s d i s s e r t a t i o n on (a) the development o f new s y n t h e t i c r o u t e s t o , and (b) t h e s t r u c -t u r a l c h a r a c t e r i z a t i o n o f n o v e l g r a p h i t e i n t e r c a l a t i o n compounds. Chemical c o n v e r s i o n s such as s u b s t i t u t i o n - , a d d i t i o n - , o x i d a t i o n - o r r e d u c t i o n - r e a c t i o n s as r o u t e s t o new a c c e p t o r i n t e r c a l a t i o n compounds o f g r a p h i t e have been s y s t e m a t i c a l l y i n v e s t i g a t e d . S u i t a b l e s t a r t i n g m a t e r i a l s C^O^F, w i t h n^ T7 as l i m i t i n g c o m p o s i t i o n , and C^BrSO^F, w i t h n ^12 f o r s t a g e 1 i n t e r c a l a t i o n compounds are formed by o x i d a t i v e i n t e r c a l a t i o n o f b i s ( f l u o r o s u l f u r y l ) p e r o x i d e , S o0 F , o r bromine ( I ) f l u o r o s u l f a t e , B r S 0 o F , r e s p e c t i v e l y . Z o Z o For CySO^F an i o n i c f o r m u l a t i o n as C^SO^F i s p r o p o s e d , however c l o s e a n i o n p a c k i n g causes c o v a l e n t a n i o n - c a t i o n i n t e r a c t i o n , p r i m a r i l y t h r o u g h oxygen, r e s u l t i n g i n backdona-t i o n o f charge and a l o w e r i n g of the i o n i c s a l t l i m i t . S u b s t i t u t i o n o f SO^F by t r i f l u o r o m e t h y l s u l f a t e , SO^CFg 5 o r h e x a f l u o r o a n t i m o n a t e ( V ) , SbFg , i s a c h i e v e d by s o l v o l y s i s o f CySO^F i n excess t r i f l u o r o m e t h y l s u l f u r i c a c i d , H S 0 3CF 3 o r antimony (V) f l u o r i d e , S b F 5 t o y i e l d C 1 2 S 0 3 C F 3 o r CgSbFg r e s p e c t i v e l y . The former i s a l s o formed from C 1 2 B r S 0 3 F and HSOgCFg. Add i t i o n of a r s e n i c CV) f l u o r i d e , A s F 5 t o CySOgF produces C 1 1 + [ A s F j . (SOgF) ] . The same r e a c t i o n t y p e , or more g e n e r a l l y " s u c c e s s i v e i n t e r c a l a t i o n " , i s used when f.luoro-s u l f u r i c a c i d , HSO-F i s added t o h i g h e r s t a g e b i n a r y g r a p h i t e f l u o r o s u l f ates , e.g. C l t +S0 3F to form a c i d f l u o r o s u l f ates, i n t h i s case Cn ,, SO_F• (HSO-F) - n c . M a t e r i a l s s i m i l a r i n composition 14 d 3 1 . U b but w i t h d i f f e r e n t spectroscopic and e l e c t r o n i c p r o p e r t i e s are formed by "simultaneous i n t e r c a l a t i o n " of c o n t r o l l e d amounts of S 20gF 2 i n HSO^F s o l u t i o n , and two d i f f e r e n t packing modes "homogeneous" and "heterogeneous" are suggested. In t ere a l a t e Oxidation i s found i n the r e a c t i o n of C 1 2 B r S 0 3 F with S 2O gF 2 to give C l g B r ( S O 3 F ) 3 , which may i n turn undergo i n t e r c a l a t e r e d u c t i o n to give C^BrSO^F. I n t e r c a l a t e d i s p r o p o r t i o n at ion and de comp o s i t i on are encountered when graphite and BrSO^F are reacted at 10 5 - 110°C to give C 2 Q B r F ( S 0 3 F ) 2 . S t r u c t u r a l models are based on X-ray powder d i f f r a c t i o n to obtain c a x i s spacings and the' stage index, Raman spectros-copy ( b a c k s c a t t e r i n g c o n f i g u r a t i o n ) to obta i n staging information from graphite l a t t i c e mode s h i f t s and to observe 19 xn r a r e cases i n t e r c a l a t e v i b r a t i o n s , F and where s u i t a b l e "^H nuclear magnetic resonance (using F o u r i e r transform techniques) to obta i n information on the nature and packing of i n t e r c a l a t e s , and l a s t but not l e a s t on complete q u a n t i t a t i v e chemical a n a l y s i s f o r information on bulk composition and sample p u r i t y . E l e c t r o n i c p r o p e r t i e s of these h i g h l y conducting m a t e r i a l s are probed o c c a s i o n a l l y by e l e c t r o n spin resonance spectroscopy and more thoroughly by measuring the b a s a l plane e l e c t r i c a l c o n d u c t i v i t i e s employing a c o n t a c t l e s s r a d i o frequency i n d u c t i o n method. i v TABLE OF CONTENTS Page Ab s t r a c t i i Table of Contents iv L i s t of Tables x L i s t of Figures x i i Glossary xv Acknowledgement x v i i CHAPTER I I n t r o d u c t i o n I.A General I n t r o d u c t i o n 2 I.B Graphite 3 I.C Graphite I n t e r c a l a t i o n Compounds (GICs) 10 I.C.I I n t e r c a l a t i o n of Graphite 10 I.C.2 GICs Which are Apparently Neither Donor Nor Acceptor Compounds 14 I.C. 3 Donor I n t e r c a l a t i o n Compounds 15 I.C.4 Acceptor I n t e r c a l a t i o n Compounds 17 I.C.5 Selected Acceptor I n t e r c a l a t i o n Compounds 18 I.D Staging Phenomenon 22 I.E Synthesis of Graphite I n t e r c a l a t i o n Compounds ... 28 I.E.I Synthetic Methods to Acceptor GICs 30 (a) Two-zone Vapour Transfer Method ... 31 (b) Isothermal Vapour Transfer Method.. 3M-(c) D i r e c t Immersion i n the I n t e r c a l a n t 35 (d) D i s s o l v e d Solute I n t e r c a l a t i o n .... 36 Ce) E l e c t r o c h e m i c a l Method 37 V I.F Selected Chemical Reactions of Acceptor GICs 40 I.G Mechanism of I n t e r c a l a t i o n 41 I.H Density of States: Band Model 43 I. I S t r u c t u r a l C h a r a c t e r i z a t i o n of Acceptor GICs 46 I . J V i b r a t i o n a l Spectra of Graphite and I t s ' I n t e r c a l a t i o n Compounds 51 I . J . I L a t t i c e Modes 52 I. J.2 I n t e r c a l a t e V i b r a t i o n s 61 I. K Purpose of This Work 61 CHAPTER I I EXPERIMENTAL I I . A.. General Comments 68 I I . B Vacuum Lines 68 I I . B . l Pyrex Vacuum Line 68 II.B.2 Metal Vacuum Line 69 II.C Reaction Vessels 70 I I . C . l Pyrex Vessels 70 II.C.2 Metal Reactor 72 II.D S p e c i a l Glass Apparatus 75 I I . D . l S 2 ° 6 F 2 A d d i t i o n T r a P S ?5 II.D.2 Vacuum F i l t r a t i o n Apparatus 77 II.E General Equipment 77 I I . E . l Dry Box 7 7 II.E.2 I.R. Spectroscopy 79 II.E.3 Raman Spectroscopy 81 II.E.4 E l e c t r o n Spin Resonance 85 II.E.5 Nuclear Magnetic Resonance 85 v i II.E.6 X-ray D i f f r a c t i o n 86 II.E.7 E l e c t r i c a l Conductance Measurements 87 (a) E l e c t r i c a l Conductance of Suspensi-ons of C ?S0 3F i n HS0 3F 87 (b) E l e c t r i c a l C o n d u c t i v i t y of GICs ... 90 I I . F Chemicals and Other M a t e r i a l s . .. 90 I I . F . l Chemicals Obtained from Commercial Sources 90-I I . F.2 Other Commercially A v a i l a b l e M a t e r i a l s .. 94 II.G P r e p a r a t i v e Reactions 97 I I . H Elemental Analyses 101 CHAPTER I I I GRAPHITE FLUOROSULFATES I I I . A I n t r o d u c t i o n 103 I I I . B Binary Graphite F l u o r o s u l f a t e s I l l I I I . B . l Synthetic Routes to Binary Graphite F l u o r o s u l f a t e s I l l (a) L i q u i d Phase I n t e r c a l a t i o n I l l (b) Vapour Phase I n t e r c a l a t i o n 115 III.B.2 Thermal Decomposition Studies on Stage 1 Binary Graphite F l u o r o s u l f a t e , C yS0 3F .. 118 I I I . B . 3 E l e c t r i c a l Conductance Measurements on Suspensions of C ?S0 3F i n HSOgF 121 II I . C Graphite A c i d F l u o r o s u l f a t e s 122 I I I . C . l Synthetic Routes to Graphite A c i d F l u o r o s u l f a t e s 122 (a) Successive I n t e r c a l a t i o n Method .. 124 (b) Simultaneous I n t e r c a l a t i o n Method. 124 v i i I I I . D . R e s u l t s a n d D i s c u s s i o n 129 I I I . E . . C o n c l u s i o n 159 CHAPTER IV GRAPHITE TRIFLUOROMETHYLSULFATES I V . A I n t r o d u c t i o n 162 IV . B S y n t h e t i c R e a c t i o n s 166 IV . C R e s u l t s a n d D i s c u s s i o n 170 IV.D C o n c l u s i o n 183 CHAPTER V INTERACTION OF FLUOROSULFATES AND A s , Sb FLUORIDES /IN IblE INTERCALATE LAYERS OF GICs V.A R e a c t i o n o f SbFj- w i t h G r a p h i t e F l u o r o s u l f a t e s .. V. A . I I n t r o d u c t i o n V.A. 2 Some P r o p e r t i e s o f S b F 5 188 V.A.3 S y n t h e s i s o f G r a p h i t e H e x a f l u o r o a n t i -monate (V) 189 V.A. 4 R e s u l t s a n d D i s c u s s i o n 190 V.B R e a c t i o n o f AsF,- w i t h G r a p h i t e f l u o r o s u l f a t e .... 199 V . B . I I n t r o d u c t i o n 199 V.B. 2 S y n t h e t i c R e a c t i o n 203 V.B. 3 R e s u l t s and D i s c u s s i o n 204 V.C R e a c t i o n o f G r a p h i t e - A s F ^ Compounds w i t h S^O^T^.. 212 V. C . I I n t r o d u c t i o n 212 V.C.2 S y n t h e t i c R e a c t i o n s 214 (a ) R e a c t i o n o f C 1 2 A s F 6 w i t h S 2 O g F 2 .... 214 (b ) R e a c t i o n o f CgAsF 5 w i t h S 2 0 g F 2 ... 215 V.C. 3 R e s u l t s a n d D i s c u s s i o n 216 V.D C o n c l u s i o n 218 v i i i C H A P T E R V I I N T E R C A L A T I O N O F H A L O G E N ' ' F L U O R O S U L F A T E S  I N T O G R A P H I T E V I . A I n t r o d u c t i o n 2 2 1 V I . B I n t e r c a l a t i o n o f B r o m i n e F l u o r o s u l f a t e s i n t o G r a p h i t e 2 2 6 V I . B . l C h e m i c a l B e h a v i o u r o f B r o m i n e F l u o r o -S u l f a t e s 2 2 6 V L B . 2 S y n t h e t i c R e a c t i o n s 2 2 7 ( a ) R e a c t i o n o f B r S O ^ F w i t h G r a p h i t e A t A m b i e n t T e m p e r a t u r e 2 2 7 ( b ) R e a c t i o n © f 3 r S 0 „ F w i t h - G r a p h i t e A t E l e v a t e d T e m p e r a t u r e s 2 3 0 ( c ) R e a c t i o n o f C - . o B r S 0 o F w i t h S o 0 c F o 12 o Z b Z ( d ) R e a c t i o n o f C y S 0 3 F w i t h B r S 0 3 F .. 2 3 2 ( e ) R e a c t i o n o f C g B r w i t h B r S O g F .... 2 3 4 V I . B . 3 R e a c t i o n s o f G r a p h i t e B r o m i n e F l u o r o -s u l f a t e s 2 3 6 ( a ) R e a c t i o n o f C 1 2 B r S 0 3 F w i t h H S 0 3 C F 3 2 3 6 ( b ) R e a c t i o n o f C 1 2 B r S 0 3 F w i t h B r 2 .. 2 3 7 ( c ) R e a c t i o n o f C ^ B r (SO.gF) 3 w i t h B r 2 2 3 7 V I . B . 4 R e s u l t s a n d D i s c u s s i o n 2 3 8 V I . C I n t e r c a l a t i o n o f C h l o r i n e ( I ) F l u o r o s u l f a t e I n t o G r a p h i t e 2 4 9 V I . C . l C h e m i c a l B e h a v i o u r o f C h l o r i n e ( I ) F l u o r o s u l f a t e 2 4 9 V I . C . 2 S y n t h e t i c R e a c t i o n 2 4 9 V I . C . 3 R e s u l t s a n d D i s c u s s i o n 2 5 0 X X V I . D A t t e m p t e d I n t e r c a l a t i o n o f I o d i n e ( I ) F l u o r o -s u l f a t e I n t o G r a p h i t e 2 5 3 V I . D . l C h e m i c a l B e h a v i o u r o f I o d i n e ( I ) • F l u o r o -s u l f a t e 2 5 3 V I . D . 2 S y n t h e t i c R e a c t i o n 2 5 3 V I . D . 3 R e s u l t s a n d D i s c u s s i o n 2 5 4 V I . E , C o n c l u s i o n 2 5 5 C H A P T E R V I I E L E C T R I C A L C O N D U C T I V I T Y O F G I C s V I L A I n t r o d u c t i o n 2 5 7 V I I . B P r e p a r a t i o n o f S a m p l e s f o r C o n d u c t i v i t y M e a s u r e m e n t s 2 6 7 V I I . B . l P r e p a r a t i o n o f B i n a r y G r a p h i t e F l u o r o -s u l f a t e s a n d G r a p h i t e A c i d " " F l u o r o s u l f a t e s 2 6 9 V I I . B . 2 P r e p a r a t i o n o f G r a p h i t e B r o m i n e F l u o r o s u l f a t e s 2 7 2 V I I . B . 3 P r e p a r a t i o n o f C S O „ C F V a n d ^ n 3 3 C S b F c 2 7 3 n 6 V I I . B . 4 P r e p a r a t i o n o f • C n [ A s F 5 ( S 0 3 F ) ] 2 7 4 V I I . C R e s u l t s a n d D i s c u s s i o n 2 7 4 V I I . D C o n c l u s i o n 2 9 3 C H A P Y E R V I I I R E F E R E N C E S A P P E N D I X C O N C L U S I O N 2 9 5 3 0 1 3 1 4 X L I S T O F T A B L E S T a b l e P a g e 1 . 1 A n i s o t r o p y F a c t o r f o r V a r i o u s T y p e s o f G r a p h i t e . . 9 1 . 2 S o m e P h y s i c a l P r o p e r t i e s o f G r a p h i t e a n d i t s I n t e r c a l a t i o n C o m p o u n d s 1 6 1 . 3 L a t t i c e V i b r a t i o n a l M o d e s o f G r a p h i t e 5 5 1 . 4 I n - p l a n e V i b r a t i o n a l M o d e s a n d C - C B o n d D i s t a n c e s o f G r a p h i t e a n d i t s I n t e r c a l a t i o n C o m p o u n d s 5 9 1 . 5 I n t e r c a l a t e V i b r a t i o n a l M o d e s o f s o m e G r a p h i t e I n t e r c a l a t i o n C o m p o u n d s 6 2 2 . 1 C h e m i c a l s O b t a i n e d f r o m C o m m e r c i a l S o u r c e s 9 1 2 . 2 C o m m e r c i a l l y A v a i l a b l e T y p e s o f A p p a r a t u s 9 6 3 . 1 S o m e P h y s i c a l P r o p e r t i e s o f S 2 0 g F 2 a n d H S O ^ F 1 1 0 3 . 2 C o m p o s i t i o n s o f B i n a r y G r a p h i t e F l u o r o s u l f a t e s O b t a i n e d b y L i q u i d P h a s e R e a c t i o n 1 1 4 3 . 3 E l e c t r i c a l C o n d u c t a n c e o f S u s p e n s i o n s o f C ^ S O ^ F i n H S 0 3 F 1 2 3 1 2 8 3 . 4 R e a c t i o n s o f G r a p h i t e w i t h M i x t u r e s o f H S O ^ F a n d S 2 0 g F 2 : E x p e r i m e n t a l D e t a i l s a n d A n a l y t i c a l D a t a . 3 . 5 I n t e r l a y e r S e p a r a t i o n s f o r v a r i o u s G r a p h i t e F l u o r o s u l f a t e s a n d A c i d S a l t s 1 4 5 3 . 6 S t r u c t u r a l a n d S p e c t r o s c o p i c P r o p e r t i e s o f B i n a r y . G r a p h i t e F l u o r o s u l f a t e s , G r a p h i t e A c i d F l u o r o s u l -f a t e s a n d R e l a t e d C o m p o u n d s 1 5 5 4 . 1 C - a x i s L a y e r R e p e a t D i s t a n c e , I , o f G . - ^ S O g C F g . . . 1 6 8 4 . 2 G r a p h i t e T r i f l u o r o m e t h y l s u l f a t e s o f S t a g e s 2 a n d 3 . . 1 6 9 x i T a b l e 4 . 3 V i b r a t i o n a l F r e q u e n c i e s o f C , „ S 0 o C F „ 1 8 0 ±•2 6 3 1 9 5 . 1 F N M R D a t a f o r G r a p h i t e H e x a f l u o r o A n t i m o n a t e s a n d R e l a t e d C o m p o u n d s 1 9 3 5 . 2 C - a x i s L a y e r R e p e a t d i s t a n c e , . I o f G r a p h i t e H e x a f l u o r o m e t a l l a t e s , ^ n + M F 6 1 9 5 5 . 3 F N M R D a t a f o r C l l + [ A s F 5 ( S O g F ) ] a n d R e l a t e d C o m p o u n d s 2 1 0 6 . 1 S o m e P h y s i c a l P r o p e r t i e s o f S e l e c t e d H a l o g e n F l u o r o s u l f a t e s 2 2 4 6 . 2 S o m e P h y s i c a l P r o p e r t i e s o f G r a p h i t e B r o m i n e F l u o r o s u l f a t e s 2 4 8 7 . 1 E l e c t r i c a l C o n d u c t i v i t y o f t h e M e t a l s U s e d t o C a l i b r a t e t h e R a d i o F r e q u e n c y I n d u c t i o n S y s t e m . . . 2 6 6 7 . 2 E l e c t r i c a l C o n d u c t i v i t y V a l u e s o f G r a p h i t e A c i d F l u o r o s u l f a t e s a n d R e l a t e d C o m p o u n d s 2 7 9 7 . 3 E l e c t r i c a l C o n d u c t i v i t y V a l u e s o f G r a p h i t e F l u o -r o s u l f a t e D e r i v a t i v e s a n d R e l a t e d C o m p o u n d s 2 8 7 7 . 4 E l e c t r i c a l C o n d u c t i v i t i e s o f C - , „ [ A s F c ( S 0 o F ) ] 14 O o a n d R e l a t e d C o m p o u n d s 2 9 1 x i i L I S T O F F I G U R E S F i g u r e P a g e 1 . 1 M o l e c u l a r S t r u c t u r e o f H e x a g o n a l G r a p h i t e 5 1 . 2 M o l e c u l a r S t r u c t u r e o f R h o m b o h e d r a l G r a p h i t e 6 1 . 3 T h e C h a i r a n d B o a t M o d e l s f o r t h e S t r u c t u r e o f P o l y ( C a r b o n M o n o f l u o r i d e ) 1 3 1 . 4 S t a g i n g P h e n o m e n o n i n G r a p h i t e I n t e r c a l a t i o n C o m p o u n d s 2 3 1 . 5 T h e D a u m a s - H e r o l d M o d e l o f S t a g i n g 2 7 1 . 6 I n t e r c h a n g e o f D o m a i n s o f S t a g e 3 a n d S t a g e 4 R e g i o n s a s m i g h t O c c u r D u r i n g a S t a g e T r a n s f o r m -a t i o n 2 9 1 . 7 T h e R a t e o f I n t e r c a l a t i o n o f V a r i o u s T y p e s o f G r a p h i t e b y M o C l j . V a p o u r N e a r S a t u r a t i o n 3 2 1 . 8 T w o - z o n e V a p o u r T r a n s f e r M e t h o d 3 3 1 . 9 A p p a r a t u s f o r t h e P r e p a r a t i o n o f G r a p h i t e I n t e r -c a l a t i o n C o m p o u n d s b y T h e E l e c t r o c h e m i c a l M e t h o d . . 3 8 1 . 1 0 D e n s i t y o f S t a t e s i n P r i s t i n e , R e d u c e d a n d O x i d i z e d G r a p h i t e a s E x p l a i n e d b y t h e B a n d M o d e l . 4 4 1 . 1 1 T h e C o r r e l a t i o n o f t h e Z o n e C e n t e r V i b r a t i o n a l M o d e s o f G r a p h i t e f o r a S i n g l e L a y e r a n d t h e 3 - d i m e n s i o n a l C r y s t a l 5 3 1 . 1 2 R a m a n a n d I n f r a r e d A c t i v e L a t t i c e M o d e s o f P r i s t i n e G r a p h i t e 5 4 1 . 1 3 R e c i p r o c a l S t a g e D e p e n d e n c e o f t h e R a m a n F r e q u e n -c i e s A s s o c i a t e d w i t h t h e G r a p h i t e L a y e r s f o r . A c c e p t o r a n d D o n o r I n t e r c a l a t i o n . C o m p o u n d s ....... . 5 8 x i i i F i g u r e 2 . 1 P y r e x R e a c t i o n V e s s e l s 7 1 2 . 2 P y r e x O n e - p a r t R e a c t i o n a n d S t o r a g e V e s s e l s 7 3 2 . 3 M o n e l M e t a l T w o - p a r t R e a c t i o n V e s s e l 7 4 2 . 4 T h e S o 0 r F o A d d i t i o n T r a p 7 6 2 . 5 V a c u u m F i l t e r 7 8 2 . 6 O p t i c a l S c h e m a t i c A r r a n g e m e n t f o r S p e c u l a r R e f l e c t a n c e • 8 0 2 . 7 T h e B r e w s t e r A n g l e . 8 2 2 . 8 B a c k s c a t t e r i n g A r r a n g e m e n t U s e d f o r R a m a n S p e c t r a . 8 4 2 . 9 C o n d u c t i v i t y C e l l 8 8 2 . 1 0 W e i g h t D r o p p e r U s e d f o r S o l u t e A d d i t i o n s 8 9 2 . 1 1 F l u o r o s u l f u r i c A c i d D i s t i l l a t i o n A p p a r a t u s 9 3 2 . 1 2 S t o r a g e V e s s e l f o r S b F 5 9 5 2 . 1 3 A p p a r a t u s f o r t h e P r e p a r a t i o n o f S 2 0 g F 2 9 8 3 . 1 F N M R S p e c t r u m o f " C r S 0 o F " 1 1 3 b o 3 . 2 A p p a r a t u s U s e d f o r T h e r m a l D e c o m p o s i t i o n S t u d i e s . . 1 1 9 3 . 3 T h e P r o p o s e d 3 - 1 a n d 2 - 2 ' M o d e s f o r t h e P a c k i n g o f S O ^ F I o n s i n t h e I n t e r c a l a t e L a y e r s o f C ^ S O ^ F . . . . 1 3 9 3 . 4 T h e P r o p o s e d S t r u c t u r e o f M ( S 0 3 F ) 2 1 4 0 19 3 . 5 F N M R S p e c t r a o f B i n a r y G r a p h i t e F l u o r o s u l f a t e s a n d G r a p h i t e A c i d F l u o r o s u l f a t e s I 1 4 7 3 . 6 1 H N M R S p e c t r a o f G r a p h i t e A c i d F l u o r o s u l f a t e s . . . . 1 4 8 3 . 7 S t r u c t u r e o f t h e a n i o n ( 0 2 F S 0 . H . 0 S F 0 2 ) " . i n C s H ( S 0 3 F ) 2 1 5 6 4 . 1 S t r u c t u r e o f t h e a n i o n S 0 „ C F ~ I 7 4 x i v F i g u r e 4 . 2 1 9 F N M R S p e c t r u m o f C - ^ S O g C F g 1 7 7 1 8 1 4 . 3 I . R . S p e c t r u m o f C 1 2 S 0 3 C F 3  5 . 1 C r y s t a l S t r u c t u r e o f K S b F g a n d P o s s i b l e O r i e n t a t -i o n s o f S b F „ I o n s i n t h e I n t e r c a l a t e L a y e r s o f b C D S b F c 1 9 7 O D 6 . 1 1 9 F N M R S p e c t r a o f C B r S O ~ F 2 2 8 ^ n 3 6 . 2 1 9 F N M R S p e c t r u m o f C ^ B r F C S O g F ) 2 3 1 1 9 6 . 3 F N M R S p e c t r u m o f t h e P r o d u c t o f t h e R e a c t i o n o f C 1 2 B r S 0 3 F w i t h S 2 0 g F 2 2 3 3 6 . 4 T h e R e a c t i o n o f C g S O . g F w i t h B r S O g F a s O b s e r v e d b y 1 9 F N M R S p e c t r o s c o p y 2 3 5 6 . 5 E 2 g 2 V i b r a t i o n a l M o d e s o f " C - ^ C l S O g F " a n d C 1 2 B r S 0 3 F 2 5 2 7 . 1 T h e C o n t a c t l e s s R a d i o F r e q u e n c y I n d u c t i o n T e c h n i q u e 2 6 2 7 . 2 A p p a r a t u s f o r t h e P r e p a r a t i o n o f G I C s f o r E l e c t r i -c a l C o n d u c t i v i t y M e a s u r e m e n t s 2 6 8 7 . 3 E l e c t r i c a l C o n d u c t i v i t y o f t h e C S 0 „ F S y s t e m 2 7 7 n 3 7 . 4 E l e c t r i c a l C o n d u c t i v i t y o f t h e C B r S 0 o F S y s t e m 2 8 5 J n 3 XV G L O S S A R Y 1 . H E X A G O N A L G R A P H I T E : T h e l a y e r s o f l i n k e d h e x a g o n s o f c a r -b o n a t o m s a r e a r r a n g e d a l o n g t h e v e r t i c a l ( c ) a x i s s u c h t h a t a l t e r n a t e l a y e r s a r e i d e n t i c a l l y p l a c e d ( A B A B . . .'. . . s e q u e n c e ) , a s i n a h e x a g o n a l c l o s e - p a c k i n g . 2. R H O M B O H E D R A L G R A P H I T E : T h e l a y e r s o f l i n k e d h e x a g o n s o f c a r b o n a t o m s a r e a r r a n g e d a l o n g t h e v e r t i c a l ( c ) a x i s s u c h t h a t e v e r y t h i r d l a y e r i s i d e n t i c a l ( A B C A B C . . . . s e q u e n c e ) . T h e s i m p l e s t u n i t f o r t h i s a r r a n g e m e n t i s a r h o m b o h e d r o n . 3 . I N T E R C A L A T I O N : I n s e r t i o n o f a t o m s , m o l e c u l e s o r i o n s i n t o a h o s t m a t e r i a l h a v i n g s u i t a b l e v a c a n t s i t e s . . 4-. I N T E R C A L A N T : T h e b u l k r e a g e n t t h a t p r o v i d e s a t o m s , m o l e c -u l e s o r i o n s f o r i n t e r c a l a t i o n . 5. I N T E R C A L A T E : A t o m s , m o l e c u l e s o r i o n s t h a t a r e i n t e r c a l a t e d i n t h e v a c a n t s i t e s o f a h o s t m a t e r i a l . 6. S T A G I N G : T h e o r d e r e d s t a c k i n g o f g r a p h i t e a n d i n t e r c a l a t e l a y e r s a l o n g t h e v e r t i c a l ( c ) a x i s o f a n i n t e r c a l a t i o n c o m p o u n d . 7 . S T A G E I N D E X : T h e n u m b e r o f c a r b o n l a y e r s s e p a r a t i n g t w o n e a r e s t i n t e r c a l a t e l a y e r s . x v i 8 . L I M I T I N G C O M P O S I T I O N : I n s o m e i n t e r c a l a t i o n r e a c t i o n s , t h e i n t e r c a l a t i o n w i l l n o t p r o c e e d a f t e r a l i m i t i n g : c o m p o s i t i o n o f t h e p r o d u c t i s r e a c h e d . T h i s l i m i t i n g c o m p o s i t i o n n e e d n o t h a v e t o b e t h a t o f a s t a g e 1 c o m p o u n d , e . g . t h e l i m i t i n g c o m p o s i t i o n C g B r r e f e r s t o a s t a g e 2 c o m p o u n d . 9 . G R A P H I T E I N T E R I O R L A Y E R S : T h e s e g r a p h i t e l a y e r s h a v e o n l y o t h e r g r a p h i t e l a y e r s a s t h e n e a r e s t n e i g h b o u r l a y e r s . 1 0 . G R A P H I T E B O U N D I N G L A Y E R S : T h e s e g r a p h i t e l a y e r s a r e a d j a -c e n t t o t h e i n t e r c a l a t e l a y e r s . 1 1 . S A N D W I C H T H I C K N E S S : T h e d i s t a n c e b e t w e e n t w o g r a p h i t e l a y e r s w i t h a n i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m . 1 2 . S K I N D E P T H : T h e s k i n d e p t h f o r t h e p e n e t r a t i o n o f a r a d i o -f r e q u e n c y f i e l d i n t o a p l a n e s l a b o f a c o n d u c t i n g m a t e r i a l i s t h e d e p t h a t w h i c h t h e i n d u c t i o n c u r r e n t d e c a y s t o 1 / e ( = 0 . 3 6 9 ) o f i t s v a l u e a t t h e s u r f a c e . x v i i ACKNOWLEDGEMENT I would l i k e to express my sin c e r e g r a t i t u d e to my research s u p e r v i s o r , Professor F. Aubke, f o r h i s able guidance and constant encouragement throughout the course of t h i s work. I am g r a t e f u l t o Professor J,G. Hooley f o r many f r u i t f u l d i s c u s s i o n s and f o r the generous g i f t of gr a p h i t e . Thanks are a l s o extended to other members of the f a c u l t y and s t a f f of t h i s department f o r t h e i r a s s i s t a n c e i n v arious aspects of t h i s r e s e a r c h , i n p a r t i c u l a r , P r o f e s s o r J . T r o t t e r f o r the use of X^-ray d i f f r a c t o m e t e r , Professor E.E. B u r n e l l and h i s student Mr. J . Rendell f o r t a k i n g some of the s o l i d s t a t e NMR s p e c t r a , the glass blowing, mechanical and e l e c t r o n i c s shops f o r c o n s t r u c t i n g most of the apparatus and Mr. P. Borda f o r microanalyses s e r v i c e s . Dr. K.C. Lee i s thanked f o r u s e f u l d i s c u s s i o n s at the i n i t i a l stages of t h i s research. I would a l s o l i k e to thank Dr. I.R. B u t l e r and Mr. G. Roberts f o r proof—reading t h i s t h e s i s and Mrs. Rani Theeparajah f o r her s k i l l and perseverance i n ty p i n g t h i s manuscript. F i n a l l y , r e c e i p t of a U n i v e r s i t y Graduate Fellowship i s g r a t e f u l l y acknowledged. 1 C H A P T E R I I N T R O D U C T I O N 2 C H A P T E R I I N T R O D U C T I O N I . A . G E N E R A L I N T R O D U C T I O N T h e n e e d f o r n o v e l m a t e r i a l s w i t h i n h e r e n t p r o p e r t i e s a d a p t a b l e t o t e c h n o l o g i c a l a p p l i c a t i o n s i s v e r y w e l l r e c o g n i z e d . T h i s n e c e s s i t y c a l l s f o r i n t e n s i v e r e s e a r c h t o e x t e n d t h e e x i s t i n g s y s t e m s , a n d t o d e v e l o p a n a l y t i c a l m e t h o d s t o c h a r a c t e r i z e n e w m a t e r i a l s . I t i s t h e r e f o r e n o t s u r p r i s i n g t h a t t h e f i e l d o f i n t e r c a l a t i o n c h e m i s t r y h a s s e e n a n e n o r m o u s i n c r e a s e i n a t t e n t i o n a n d a c t i v i t y . I n t h i s m a t t e r g r a p h i t e i n t e r c a l a t i o n c o m p o u n d s ( G I C s ) a r e v i e w e d a s p r o m i s i n g c a n d i d a t e s f o r e l e c t r i c a l e n e r g y s t o r a g e s y s t e m s a n d p l a n a r -1 - 3 c o n d u c t o r s d u e t o t h e i r d o c u m e n t e d i n c r e a s e d b a s a l p l a n e c o n d u c t i v i t y , a n d l i g h t w e i g h t . N e v e r t h e l e s s t h e i r p o t e n t i a l 4 f o r c a t a l y t i c a p p l i c a t i o n s h a s a l s o c o n t r i b u t e d t o t h e r e n e w e d i n t e r e s t i n t h e s e s y s t e m s . I n a d d i t i o n t o t h i s t e c h n o l o g i c a l p o t e n t i a l , G I C s a r e a n i n t e r e s t i n g c l a s s o f m a t e r i a l t o c h e m i s t s d u e t o t h e i r v e r s a t i l i t y f o r 2 D m a t r i x s t u d i e s . 5 U b b e l o h d e w a s t h e f i r s t t o r e p o r t t h e i n c r e a s e d e l e c t r i c a l c o n d u c t i v i t y o f G I C s , a n d t o c o i n t h e t e r m 1 - 3 " s y n t h e t i c m e t a l s " . S u b s e q u e n t s t u d i e s o n g r a p h i t e - g r o u p V p e n t a f l u o r i d e s y s t e m s s h e d m o r e l i g h t o n a c c e p t o r G I C s a s n o v e l c o n d u c t o r s . T h e a n i s o t r o p i c n a t u r e o f g r a p h i t e a s w e l l a s o f t h e i n t e r c a l a t i o n c o m p o u n d s s u g g e s t e d t h e p h y s i c a l 3 p r o p e r t i e s t o b e h i g h l y t w o d i m e n s i o n a l u n l i k e m e t a l l i c c o n d u c t i o n i n c o p p e r o r a l u m i n u m . T h e i n t e n s i v e r e s e a r c h a c t i v i t y i n g r a p h i t e i n t e r c a l a t i o n c o m p o u n d s i s e v i d e n c e d b y t h e p u b l i c a t i o n o f a t l e a s t t w e l v e m a j o r r e v i e w a r t i c l e s i n t h e l a s t t w o y e a r s , t o u p d a t e a n d s u m m a r i z e t h e s y n t h e t i c , s t r u c t u r a l a n d p h y s i c a l a s p e c t s o f t h e s e m a t e r i a l s . A m o n g t h e s e , t h e r e v i e w b y S e l i g a n d E b e r t d e s c r i b e s t h e t y p e s o f G I C s a l r e a d y s y n t h e s i z e d , i n d i c a t i n g t h e i r s t r u c t u r a l f e a t u r e s , a n d p h y s i c a l p r o p e r t i e s . A n 7 e x t e n s i v e r e v i e w a r t i c l e b y D r e s s e l h a u s a n d D r e s s e l h a u s c o v e r s v i r t u a l l y a l l t h e a s p e c t s o f p h y s i c a l a n d t e c h n o l o g i c a l i n t e r e s t s , o f t h e s e m a t e r i a l s . T h e c h e m i s t r y o f G I C s h a s 8 9" b e e n r e v i e w e d b y B a r t l e t t e t a l . a n d F o r s m a n e t a l . E l e c t r o n i c p r o p e r t i e s a n d r e l a t e d s t r u c t u r a l m o d e l s o f t h e s e 1 0 1 1 . 1 2 s y s t e m s h a v e b e e n d e s c r i b e d b y F i s h e r ' a n d S o l i n r e s p e c t i v e l y . S i n c e t h e p r i n c i p a l f e a t u r e s o f G I C S a r e b e s t v i e w e d a s e i t h e r e x t e n s i o n s , o r a s s u i t a b l e m o d i f i c a t i o n s o f t h e c o r r e s p o n d i n g p r o p e r t i e s o f g r a p h i t e i t s e l f , a d e t a i l e d s u m m a r y o f t h e s t r u c t u r a l a s p e c t s a n d p h y s i c a l p r o p e r t i e s o f g r a p h i t e i s a t t e m p t e d i n t h e f o l l o w i n g s e c t i o n " ; ' . I . B . G R A P H I T E 1 5 G r a p h i t e h a s a p r o t o t y p i c a l l a y e r s t r u c t u r e N a t u r a l g r a p h i t e e x i s t s i n t w o a l l o t r o p i c f o r m s : h e x a g o n a l , a n d r h o m b o h e d r a l . T h e m o r e c o m m o n h e x a g o n a l f o r m i s c h a r a c t e r i z e d b y a n A B A B . . . l a y e r a r r a n g e m e n t a l o n g t h e v e r t i c a l a x i s , w h e r e A , B a s w e l l a s C i n d i c a t e p o s i t i o n a l l y 4 d i f f e r e n t l a y e r s . T h e m o l e c u l a r s t r u c t u r e o f h e x a g o n a l g r a p h i t e i s s h o w n i n F i g . 1 . 1 . T h e r h o m b o h e d r a l f o r m h a s i t s c a r b o n l a y e r s a r r a n g e d i n a n A B C A B C s e q u e n c e a l o n g t h e v e r t i c a l a x i s , a s s h o w n i n F i g . 1 . 2 . T h i s t y p e o f g r a p h i t e i s r a r e l y o b s e r v e d , a n d h a s n o t b e e n u s e d e x t e n s i v e l y a s h o s t 1 2 i t m a t e r i a l f o r i n t e r c a l a t i o n . T h e r e f o r e t h e t e r m g r a p h i t e u s e d t h r o u g h o u t t h i s t h e s i s , r e f e r s t o t h e h e x a g o n a l f o r m o f g r a p h i t e . T h e i n d i v i d u a l l a y e r s m a y b e v i e w e d a s a n i n f i n i t e s h e e t o f r e g u l a r , i n t e r c o n n e c t e d h e x a g o n s ( s e e F i g . 1 . 1 ) . 2 B o n d i n g m t h e b a s a l p l a n e s o f g r a p h i t e h a s e a c h s p h y b r i d i z e d c a r b o n a t o m f o r m t h r e e a b o n d s w i t h t h e n e i g h b o u r i n g c a r b o n a t o m s . T h e r e m a i n i n g f o u r t h v a l e n c e e l e c t r o n o f e a c h c a r b o n a t o m c o n t r i b u t e s t o d e l o c a l i z e d i r - e l e c t r o n d e n s i t y a b o u t t h e g r a p h i t e l a y e r . T h e r e s u l t i n g h i g h m o b i l i t y o f c h a r g e c a r r i e r s c a u s e s t h e e l e c t r i c a l t r a n s p o r t p r o p e r t i e s o f g r a p h i t e i n t h e b a s a l p l a n e . T h e i n t e r n u c l e a r C - C s e p a r a t i o n i n t h e b a s a l p l a n e i s 1 . 4 2 1 A , a n d t h e i n t e r l a y e r s e p a r a t i o n i s 3 . 3 5 A , 8 i n d i c a t i v e o f w e a k V a n d e r W a a l ' s i n t e r l a y e r b o n d i n g . C o n v e r s e l y t h e i n v o l v e m e n t o f i r - e l e c t r o n s i n a d j a c e n t c a r b o n 1 3 p l a n e s h a s b e e n r e p o r t e d t o c o n t r i b u t e t o w e a k i n t e r l a y e r b o n d i n g b e t w e e n t h e p l a n e s . T h e w e a k n e s s o f t h e s e i n t e r p l a n e r f o r c e s i s r e s p o n s i b l e f o r b o t h p h y s i c a l a n d c h e m i c a l p r o p e r -t i e s . T h e " l a y e r " a p p e a r a n c e , t h e l u b r i c a n t p r o p e r t i e s a n d t h e a b i l i t y t o f o r m l a m e l l a r c o m p o u n d s a r e m o s t o b v i o u s a m o n g t h e m . T h e r e a r e v a r i o u s t y p e s o f g r a p h i t e t h a t h a v e b e e n u s e d a s h o s t m a t e r i a l s : n a t u r a l g r a p h i t e , p y r o l y t i c g r a p h i t e a n d 5 F I G . 1 . 1 M O L E C U L A R S T R U C T U R E O F H E X A G O N A L G R A P H I T E ( F R O M R E F E R E N C E 1 2 ) 6 F I G . 1 . 2 M O L E C U L A R S T R U C T U R E O F R H O M B O H E D R A L • G R A P H I T E ( F R O M R E F E R E N C E 7 ) 7 K i s h g r a p h i t e . N a t u r a l g r a p h i t e c r y s t a l s c a n b e f o u n d i n a n u m b e r o f l o c a t i o n s , s u c h a s M a d a g a s c a r , C e y l o n a n d t h e T i c o n d e r o g a a r e a o f t h e U . S . I n t h e l a t t e r c a s e , f a i r l y l a r g e c r y s t a l s s e v e r a l m m i n t h e b a s a l p l a n e s , ^ 1 m m t h i c k n e s s ) 1 3 c a n b e o b t a i n e d . N a t u r a l l y o c c u r r i n g c r y s t a l s o f g r a p h i t e c o n t a i n i m p u r i t i e s s u c h a s F e , C a a n d s i l i c a t e s , w h i c h c a n b e r e m o v e d b y c h e m i c a l l e a c h i n g . T y p i c a l l e a c h i n g m e t h o d s e m p l o y b o i l i n g t h e m a t e r i a l i n c o n c e n t r a t e d H F o r h e a t i n g ( ^ 2 0 0 0 ° C ) i n f l o w i n g g a s . T h e l a r g e r c r y s t a l s a r e o f t e n u n s u i t a b l e f o r t h e s y n t h e s i s o f G I C s f o r t h e p u r p o s e o f p h y s i c a l m e a s u r e m e n t s , s i n c e t h e y c o n t a i n m a n y c r y s t a l d e f e c t s a n d s t r u c t u r a l i m p e r f e c t i o n s . S o m e o f t h e s e d e f e c t s o f n a t u r a l g r a p h i t e m a y b e c a r r i e d o v e r t o t h e i n t e r c a l a t i o n c o m p o u n d , a n d h e n c e a f f e c t i t s p h y s i c a l p r o p e r t i e s . P y r o l y t i c g r a p h i t e i s a m o n o l i t h i c g r a p h i t e m a t e r i a l o b t a i n e d b y h e a t t r e a t m e n t o f p y r o l y t i c c a r b o n o r b y c h e m i c a l v a p o u r d e p o s i t i o n a t t e m p e r a t u r e s a b o v e 2 1 0 0 K . H o t - p r e s s i n g o f p y r o l y t i c g r a p h i t e a t t e m p e r a t u r e s a b o v e 2 8 0 0 K r e s u l t s i n a n o t h e r s y n t h e t i c g r a p h i t e , k n o w n a s h i g h l y o r i e n t e d p y r o l y t i c 7 1 3 1 4 g r a p h i t e ( H O P G ) ' ' . H O P G i s o f t e n u s e d a s s t a r t i n g m a t e r i a l f o r i n t e r c a l a t i o n r e a c t i o n s . T h i s t y p e o f g r a p h i t e c o n s i s t s o f m i c r o c r y s t a l l i t e s w i t h t y p i c a l p l a n a r ( a - a x i s ) a n d v e r t i c a l ( c - a x i s ) d i m e n s i o n s o f 1 a n d 1 0 y m , r e s p e c t i v e l y . T h e c - a x e s o f t h e s e c r y s t a l s a r e a l i g n e d w i t h i n ^ 0 . 2 ° , b u t t h e a - a x e s a r e r a n d o m l y o r i e n t e d . I t i s o f t e n u s e d t o p r e p a r e b u l k s p e c i m e n s o f G I C s 1 s u i t a b l e f o r s t r u c t u r a l s t u d i e s a n d p h y s i c a l m e a s u r e m e n t s . T h e g r e a t e r f l e x i b i l i t y o f t h e s i z e s . 8 o f H O P G p l a t e s a v a i l a b l e m a k e s i t a f a v o u r a b l e h o s t m a t e r i a l , w h i c h h a s b e e n e x t e n s i v e l y u s e d t o p r e p a r e G I C s i n t h e l a s t 7 d e c a d e . T h e s o l e d i s a d v a n t a g e o f H O P G a s h o s t m a t e r i a l i s i t s p o l y c r y s t a l l i n e n a t u r e , t h a t d o e s n o t a l l o w d e t a i l e d s t r u c t u r a l s t u d i e s a s d o e s s i n g l e c r y s t a l g r a p h i t e . T h e r e m a y a l s o b e d i s c r e p a n c i e s i n t h e i n t e r p r e t a t i o n o f t r a n s p o r t 7 p r o p e r t y d a t a o b t a i n e d u s i n g s a m p l e s p r e p a r e d f r o m H O P G . A n o t h e r t y p e o f s y n t h e t i c g r a p h i t e p o t e n t i a l l y s u i t a b l e a s t h e h o s t m a t e r i a l i s K i s h g r a p h i t e ( K G ) . K i s h g r a p h i t e i s o b t a i n e d b y c r y s t a l l i z a t i o n o f c a r b o n f r o m F e - C m e l t s , a n d m a y t h e r e f o r e c o n t a i n F e a s t h e p r i n c i p a l i m p u r i t y . C r y s t a l s o f K i s h g r a p h i t e a r e n o r m a l l y a n o r d e r o f m a g n i t u d e g r e a t e r i n a r e a a n d i n t h i c k n e s s w h e n c o m p a r e d t o n a t u r a l s i n g l e c r y s t a l f l a k e s . C a r b o n f i b e r s h a v e a l s o b e e n u s e d i n i n t e r c a l a t i o n 3 1 r e a c t i o n s . C a r b o n f i b e r s p o s s e s s g r e a t m e c h a n i c a l s t r e n g t h , s i n c e t h e f i b e r a x i s f a l l s a l o n g t h e s t r o n g l y b o n d e d a - a x e s o f g r a p h i t e c r y s t a l s . A m a j o r d i f f e r e n c e a n d a n i m p o r t a n t c r i t e r i o n a p p l i e d t o t h e s e v a r i o u s t y p e s o f g r a p h i t e i s t h e a n i s o t r o p y r a t i o ( 0 a 7 ) , w h e r e a i s t h e e l e c t r i c a l c o n d u c t a n c e i n o h m " ' " c m "'". T a b l e 1 . 1 s h o w s t h e c - a x i s c o n d u c t i v i t y ( a ) a n d t h e a n i s o t r o p y r a t i o ( C T a / ) f o r n a t u r a l , a n d s y n t h e t i c g r a p h i t e s . N a t u r a l g r a p h i t e s o b t a i n e d f r o m v a r i o u s p l a c e s s h o w v e r y l o w a n i s o t r o p y CTa7 - ( 1 0 0 - 1 7 0 ) , a t 3 0 0 K b u t H O P G a n d p y r o l y t i c g r a p h i t e s a r e h i g h l y a n i s o t r o p i c . T h e m a i n c o n t r i b u t o r t o a n i s o t r o p y i n t h i s m a t e r i a l i s t h e d e c r e a s e d i n t e r a c t i o n b e t w e e n t h e c a r b o n 9 T A B L E 1 . 1 : A N I S O T R O P Y F A C T O R F O R V A R I O U S T Y P E S O F G R A P H I T E ( F r o m R e f e r e n c e 1 3 ) M a t e r i a l T ( K ) - 1 - 1 a a ( o h m c m ) ( — ) c a c N a t u r a l g r a p h i t e ( C e y l o n , M e x i c o ) 3 0 0 . 3 x 1 0 1 0 0 N a t u r a l g r a p h i t e ( C e y l o n ) 3 0 0 1 0 1 0 4 N a t u r a l g r a p h i t e ( T i c o n d e r o g a ) 3 0 0 1 . 5 - 2 . 3 x 1 0 1 1 0 - 1 7 0 N a t u r a l g r a p h i t e ( T i c o n d e r o g a ) 3 0 0 2 x 1 0 1 3 0 N a t u r a l g r a p h i t e ( T i c o n d e r o g a ) 3 0 0 3 . 3 x 1 0 8 0 K i s h g r a p h i t e 3 0 0 1 . 3 - 1 . 5 x 1 0 P y r o l y t i c c a r b o n ( T . = 2 2 0 0 ° C ) d P y r o l y t i c c a r b o n ( T . = 2 5 0 0 ° C ) d P y r o l y t i c g r a p h i t e ( H T T = 3 0 0 0 ° C ) 3 0 0 3 0 0 3 0 0 1 2 5 8 3 3 8 5 5 5 0 0 5 0 0 0 5 2 0 0 H O P G ( a n n e a l e d 3 5 0 0 ° C ) 3 0 0 5 9 0 3 8 0 0 1 0 p l a n e s a l o n g t h e c - a x i s a s i n d i c a t e d b y t h e v e r y l o w c - a x i s c o n d u c t i v i t y o f p y r o l y t i c g r a p h i t e s c o m p a r e d t o t h e n a t u r a l g r a p h i t e s . T h i s p r o n o u n c e d t w o - d i m e n s i o n a l c h a r a c t e r m a k e s H O P G a n i d e a l s t a r t i n g m a t e r i a l f o r t h e s y n t h e s i s o f t w o -d i m e n s i o n a l c o n d u c t o r s . W h a t e v e r t y p e o f g r a p h i t e i s - u s e d , t h e r e s p o n s e i n i n t e r c a l a t i o n r e a c t i o n s a n d t h e p r o p e r t i e s o f t h e p r o d u c t f o r m e d a r e d e t e r m i n e d b y s e v e r a l f a c t o r s : ( i ) l a t t i c e p e r f e c t i o n ( i i ) c r y s t a l l i t e s i z e ( i i i ) s t r u c t u r a l d e f e c t s a n d ( i v ) n a t u r e o f i n t e r c a l a t i n g s u b s t a n c e . I . C . G R A P H I T E I N T E R C A L A T I O N C O M P O U N D S ( G I C s ) I . C . I I N T E R C A L A T I O N O F G R A P H I T E T h e t e r m " i n t e r c a l a t i o n " i m p l i e s i n s e r t i o n o f a t o m s , m o l e c u l e s , o r i o n s ( g u e s t s p e c i e s ) i n t o a h o s t m a t e r i a l h a v i n g 1 7 s u i t a b l e v a c a n t l a m e l l a r s x t e s . T h e s t r u c t u r a l f e a t u r e s o f " t h e h o s t r e m a i n e s s e n t i a l l y u n c h a n g e d u p o n i n t e r c a l a t i o n . T h e f o r m a t i o n o f a G I C w a s f i r s t r e p o r t e d b y 1 8 S c h a f h a e u t l , i n 1 8 4 0 , a s t h e s w e l l i n g o f n a t u r a l g r a p h i t e 1 9 w h e n t r e a t e d w i t h a c i d s . H o w e v e r , F r e d e n h a g e n a n d C a d e n b a c h w e r e t h e f i r s t t o r e p o r t a s y s t e m a t i c s y n t h e s i s o f i n t e r c a l a t i o n c o m p o u n d s b y t h e r e a c t i o n o f p o t a s s i u m m e t a l v a p o u r w i t h g r a p h i t e u s i n g a t w o - z o n e v a p o u r p h a s e s y n t h e s i s m e t h o d . S t u d i e s o f t h e p h y s i c a l p r o p e r t i e s o f t h e s e c o m p o u n d s w e r e i n i t i a t e d i n t h e e a r l y 1 9 3 0 ' s , w i t h t h e i n t r o d u c t i o n o f X - r a y d i f f r a c t i o n t e c h n i q u e s . D u r i n g t h i s p e r i o d t h e l a m e l l a r n a t u r e o f t h e s e m a t e r i a l s , w i t h s u c c e s s i v e h o s t a n d g u e s t l a y e r s 2 0 2 1 w a s f i r s t r e a l i z e d ' . T h e g u e s t s p e c i e s w e r e s u b s e q u e n t l y 1 1 r e f e r r e d t o a s " i n t e r c a l a t e s " a n d t h e b u l k m a t e r i a l u s e d t o p r o v i d e m o l e c u l e s f o r i n t e r c a l a t i o n c a l l e d " i n t e r c a l a n t " . T h e r e n e w e d i n t e r e s t s i n t h e s e m a t e r i a l s d u r i n g t h e l a s t d e c a d e h a s c o n t r i b u t e d l a r g e l y t o t h e s y n t h e s i s o f s e v e r a l n o v e l i n t e r c a l a t i o n c o m p o u n d s . T h e s e c o m p o u n d s c a n b e d i v i d e d i n t o t h r e e m a j o r g r o u p s a c c o r d i n g t o t h e n a t u r e o f t h e g u e s t -h o s t i n t e r a c t i o n i n v o l v e d d u r i n g t h e i r f o r m a t i o n : ( i ) D o n o r c o m p o u n d s - C o m p o u n d s f o r m e d b y e l e c t r o n d o n o r i n t e r c a l a n t s , e . g . N a , K ( i i ) A c c e p t o r c o m p o u n d s - C o m p o u n d s f o r m e d b y e l e c t r o n a c c e p t o r i n t e r c a l a n t s , e . g . S b F ^ , B r 2 ( i i i ) I n t e r c a l a t i o n c o m p o u n d s w h i c h a r e a p p a r e n t l y n e i t h e r d o n o r n o r a c c e p t o r c o m p o u n d s . T h e r e a r e t w o l i m i t i n g c a s e s f o r t h e i n t e r a c t i o n o f a b u l k i n t e r c a l a n t w i t h g r a p h i t e : ( i ) a t t a c k o f t h e c a r b o n l a y e r b y t h e i n t e r c a l a n t m o l e c u l e s r e s u l t i n g i n c o v a l e n t b o n d f o r m a t i o n a n d h e n c e c h e m i c a l m o d i f i c a t i o n o f t h e l a y e r s t r u c t u r e , ( i i ) A d s o r p t i o n a n d c a p i l l a r y c o n d e n s a t i o n o n g r a p h i t e . C o v a l e n t c o m p o u n d s o f g r a p h i t e a r e f o r m e d w h e n g r a p h i t e i s r e a c t e d w i t h s t r o n g o x i d i z i n g a g e n t s s u c h a s f l u o r i n e a n d g M n ( V I I ) . T h e f o r m a t i o n o f c o v a l e n t b o n d s a t t h e c a r b o n a t o m s o f t h e h o s t r e s u l t s i n l o s s o f p l a n a r i t y o f c a r b o n l a y e r s t o 1 2 f o r m a p u c k e r e d a r r a n g e m e n t o f s p h y b r i d i z e d c a r b o n a t o m s . A t y p i c a l e x a m p l e f o r t h i s t y p e o f c o m p o u n d s i s p o l y ( c a r b o n m o n o f l u o r i d e ) , ( C F ) . T h e s t r u c t u r e o f e a c h l a y e r o f t h i s m a t e r i a l c a n b e d e s c r i b e d b y t h e c h a i r a n d b o a t m o d e l s a s s h o w n i n F i g . 1 . 3 . T h e m a i n t e n a n c e o f t h e l a y e r e d s t r u c t u r e i n p o l y ( c a r b o n m o n o f l u o r i d e ) i s e x p l o i t e d i n i t s u s e a s a l u b r i c a n t . W h e n t h e i n t e r a c t i o n o f t h e i n t e r c a l a n t w i t h g r a p h i t e i s r a t h e r w e a k , i t w o u l d o n l y r e s u l t i n a d s o r p t i o n a n d c o n d e n s a t i o n o f t h e i n t e r c a l a n t o n g r a p h i t e . I n t h i s c a s e t h e i n t e r c a l a n t m o l e c u l e s a r e b o u n d t o t h e s u r f a c e b y w e a k V a n d e r W a a l ' s t y p e f o r c e s . T h e r e f o r e e x p o s u r e o f t h e s a m p l e t o a d y n a m i c v a c u u m w o u l d r e s u l t i n t h e r e m o v a l o f t h e a d s o r b e d a n d c o n d e n s e d m a t e r i a l . T h e o o v a l e n t b o n d f o r m a t i o n o n t h e o t h e r h a n d i s r a t h e r i r r e v e r s i b l e a n d t h e c o v a l e n t c o m p o u n d s o f g r a p h i t e a r e s t a b l e i n a v a c u u m e v e n a t e l e v a t e d t e m p e r a t u r e s . T h e i n t e r c a l a t i o n c o m p o u n d s w o u l d d e i n t e r c a l a t e a t e l e v a t e d t e m p e r a t u r e s u n t i l a p a r t i c u l a r c o m p o s i t i o n i s r e a c h e d a f t e r w h i c h t h e e x t e n t o f d e i n t e r c a l a t i o n w o u l d b e n e g l i g i b l e . T h e r e s u l t i n g m a t e r i a l , c a l l e d a " r e s i d u e n c o m p o u n d " , w o u l d h a v e a n i n t e r c a l a n t c o n t e n t d e p e n d e n t o n t h e t e m p e r a t u r e o f d e i n t e r c a l a t i o n . H o w e v e r , t h e i n t e r c a l a t e c a n n o t b e c o m p l e t e l y d e i n t e r c a l a t e d a t a n y t e m p e r a t u r e . T h e i n t e r c a l a t i o n c o m p o u n d s f o r m a b r o a d s p e c t r u m c o n s i s t i n g o f m a t e r i a l s p r e p a r e d f r o m t w o , o r t h r e e d i m e n s i o n a l s o l i d s s u c h a s g r a p h i t e , s i l i c a t e s a n d z e o l i t e s . T h e m a t e r i a l s o b t a i n e d b y d o p i n g o r g a n i c p o l y m e r s s u c h a s p o l y a c e t y l e n e a n d p o l y p r o p y l e n e w i t h e l e c t r o n d o n o r a n d 1 3 ( A ) ( B ) F I G . 1 . 3 ( A ) T H E C H A I R A N D ( B ) B O A T M O D E L S F O R T H E S T R U C T U R E O F P O L Y ( C A R B O N M O N O F L U O R I D E ) ( F R O M R E F E R E N C E 6 ) T H E S O L I D . A N D O P E N C I R C L E S D E N O T E T H E C A R B O N A N D F L U O R I N E A T O M S R E S P E C T I V E L Y 1 4 a c c e p t o r s p e c i e s , a l s o f o r m a c l o s e l y r e l a t e d c l a s s o f c o m p o u n d s . H o w e v e r , t h i s d i s c u s s i o n i s r e s t r i c t e d t o i n t e r -c a l a t i o n , c o m p o u n d s o f g r a p h i t e ; s p e c i f i c a l l y t o t h e s y n t h e t i c a n d s t r u c t u r a l a s p e c t s , w h i c h f o r m t h e p r i n c i p a l p a r t o f t h i s d i s s e r t a t i o n . I . C . 2 I N T E R C A L A T I O N C O M P O U N D S W H I C H A R E A P P A R E N T L Y N E I T H E R  D O N O R N O R A C C E P T O R C O M P O U N D S I n s o m e G I C s t h e r e i s n o e v i d e n c e f o r c h a r g e t r a n s f e r a n d t h e i n t e r c a l a t e s a p p e a r t o r e m a i n a s n e u t r a l m o l e c u l e s . S o m e n o b l e g a s f l u o r i d e s ( e . g . K r F 2 ) a n d h a l o g e n f l u o r i d e s g ( e . g . B r F „ ) a r e k n o w n t o f o r m G I C s t h a t f a l l i n t h i s g r o u p . T h e s e i n t e r c a l a n t s a r e p o w e r f u l e n o u g h t o o x i d i z e g r a p h i t e , h o w e v e r i n t h e c a s e o f K r F 2 f o r m a t i o n o f r e d u c e d s p e c i e s s u c h a s K r F 2 o r K r F ^ a p p e a r s u n l i k e l y w h i l e f o r m a t i o n o f c o v a l e n t C - F b o n d s b e c o m e s a d e f i n i t e p o s s i b i l i t y . I n t h e c a s e o f B r F ^ t h e r e i s e x t e n s i v e e v o l u t i o n o f B r 2 a n d B r F ^ h a s b e e n r e p o r t e d l y f o r m e d . A g a i n f l u o r i n a t i o n o f g r a p h i t e i s l i k e l y . I t h e n c e a p p e a r s t h a t n o n o t i c e a b l e c h a n g e i n c o n d u c t i v i t y m a y b e d u e t o a c o m p l e x i n t e r a c t i o n w i t h C - F b o n d f o r m a t i o n l i k e l y . H o w e v e r , m o s t o f t h e i n t e r c a l a t i o n c o m p o u n d s c l e a r l y s h o w e v i d e n c e f o r c h a r g e t r a n s f e r b e t w e e n t h e i n t e r c a l a t e a n d g r a p h i t e . D e p e n d i n g o n t h e d i r e c t i o n o f c h a r g e t r a n s f e r t h e s e i n t e r c a l a t i o n c o m p o u n d s a r e c a l l e d d o n o r o r a c c e p t o r c o m p o u n d s . 1 5 I . C . 3 D O N O R I N T E R C A L A T I O N C O M P O U N D S • D o n o r i n t e r c a l a t i o n c o m p o u n d s a r e f o r m e d b y i n t e r c a l a t -i n g g r a p h i t e w i t h e l e c t r o p o s i t i v e e l e m e n t s w i t h l o w f i r s t i o n i z a t i o n p o t e n t i a l s s u c h a s L i , K , R b , C s a n d B a . A s t h e n a m e i m p l i e s t h e a b i l i t y t o d o n a t e e l e c t r o n s r e a d i l y t o g r a p h i t e i s t h e m a i n b o n d i n g c o n t r i b u t o r . T h i s p r e c i s e l y i s t h e r e a s o n t h a t L e w i s b a s e s s u c h a s N H g d o n o t i n t e r c a l a t e b y t h e m s e l v e s . A m m o n i a h a s b e e n f o u n d t o c o i n t e r c a l a t e w i t h s o m e m e t a l s , w h e n t h e s e m e t a l s a r e d i s s o l v e d i n l i q u i d N H ^ , t o f o r m c o m p o u n d s o f t h e c o m p o s i t i o n C^^MCRE^)^, w h e r e M = L i , N a , 2 2 . . . K , R b , C s , S r a n d B a . I n a d d i t i o n t o f o r m i n g b i n a r y c o m -p o u n d s ( e . g . C g L i , C g K ) , a l k a l i m e t a l s h a v e b e e n f o u n d t o c o i n t e r c a l a t e a s a l l o y s . T h e s e t e r n a r y c o m p o u n d s h a v e a g e n e r a l 1 2 3 1 s t o i c h i o m e t r y o f C Q M M , n , w h e r e M , M = K , R b a n d C s . J 8 x ( 1 - x ) ' ' ' T h e p r o p e r t i e s o f d o n o r i n t e r c a l a t i o n c o m p o u n d s s t r o n g l y r e f l e c t t h e i n t e r a c t i o n s b e t w e e n c a r b o n a n d i n t e r c a l a t e l a y e r s . A s s h o w n i n T a b l e 1 . 2 t h e c - a x i s c o n d u c t i v i t y o f d o n o r c o m p o u n d s i s g r e a t e r t h a n t h a t o f g r a p h i t e b y a n o r d e r 2 . . . . o f ^ 1 0 w h i l e t h e a - a x i s c o n d u c t i v i t y i s i n c r e a s e d o n l y b y a n o r d e r o f ^ 1 0 . T h i s c a u s e s t h e l o w e r a n i s o t r o p y , ( a a / ) o f a c d o n o r c o m p o u n d s t h a n £ h a t e x h i b i t e d b y g r a p h i t e i t s e l f . A n o t h e r i n t e r e s t i n g d i f f e r e n c e b e t w e e n d o n o r a n d a c c e p t o r G I C s i s f o u n d i n t h e s e p a r a t i o n b e t w e e n t w o c a r b o n l a y e r s w i t h a n i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m , t e r m e d I : " . T h e J s d i s t a n c e I , f o r d o n o r c o m p o u n d s i s r a t h e r s m a l l , b e t w e e n ^ 4 s o a n d 6 A , c o m p a r e d t o t h e a c c e p t o r c o m p o u n d s d u e t o t h e f a c t t h a t d o n o r s p e c i e s a r e c o m m o n l y m o n o a t o m i c w h i l e a c c e p t o r s 1 6 T A B L E 1 . 2 : S O M E P H Y S I C A L P R O P E R T I E S O F G R A P H I T E A N D I T S I N T E R C A L A T I O N C O M P O U N D S ( D a t a c o l l e c t e d f r o m R e f e r e n c e s 1 1 a n d 2 4 ) M a t e r i a l - 1 - 1 , I ( A ) a ( o h m c m ) a ( o h m c m - 1 - 1 — G r a p h i t e 3 . 3 5 2 . 5 x 1 0 ^ 1 0 ^ 2 . 5 x 1 0 ' a. D O N O R G I C s C c L i b 3 . 7 0 2 . 6 x 1 0 1 . 7 x 1 0 1 5 . 3 5 . 4 0 1 . 0 x 1 0 5 3 . 0 x 1 0 3 . 3 3 . 3 C n R b 5 . 6 5 1 . 0 x 1 0 ' 1 2 0 C n C s 5 . 9 4 1 . 0 x 1 0 5 5 . 0 x 1 0 3 2 0 . 0 A C C E P T O R G I C s C C H O 0 b o 7 . 7 8 3 . 0 x 1 0 ' 2 . 0 1 . 5 x 1 0 ' C 6 H 2 S ° 4 7 . 9 8 1 . 0 x 1 0 ' 0 . 5 2 . 0 x 1 0 ' C 8 A S F 5 8 . 1 1 4 . 0 x 1 0 ' 0 . 2 2 . 0 x 1 0 C „ B r 7 . 0 5 2 . 0 x 1 0 ' 7 . 0 x 1 0 1 7 a r e m o l e c u l a r a g g r e g a t e s . F i s c h e r h a s s h o w n t h a t t h e d i s t a n c e I f o r d o n o r c o m p o u n d s i s m u c h s h o r t e r t h a n t h e i d e a l s e p a r a t i o n e x p e c t e d a s s u m i n g a c o m p l e t e l y i o n i c m o d e l f o r 7 . t h e s e c o m p o u n d s . R a m a n s t u d i e s o f m - p l a n e C - C v i b r a t i o n s o f d o n o r c o m p o u n d s h a v e s h o w n t h a t t h e c h a r g e t r a n s f e r r e d f r o m d o n o r a t o m s t o c a r b o n l a y e r s s h o u l d l a r g e l y b e c o n f i n e d t o t h e a d j a c e n t l a y e r s . A l l e v i d e n c e i n d i c a t e t h a t d o n o r i n t e r c a l a t e s n o t o n l y r e d u c e a d j a c e n t c a r b o n l a y e r s , b u t a l s o i n t e r a c t w i t h t h e s e l a y e r s b y o r b i t a l m i x i n g , r e s u l t i n g p o s s i b l y i n w e a k m e t a l - c a r b o n b o n d s . I . C . 4 A C C E P T O R I N T E R C A L A T I O N C O M P O U N D S I n t e r c a l a t i o n o f g r a p h i t e w i t h e l e c t r o n a c c e p t o r s t h a t p o s s e s s s u f f i c i e n t e l e c t r o n a f f i n i t y t o w i t h d r a w I T e l e c t r o n d e n s i t y f r o m t h e c a r b o n l a y e r s r e s u l t s i n t h e f o r m a t i o n o f a c c e p t o r G I C s . I n c o n t r a s t t o d o n o r c o m p o u n d s , , t h e a c c e p t o r m o l e c u l e s w h i c h p a r t i c i p a t e i n o x i d a t i o n r e a c t i o n s r e m a i n i o n i z e d a n d t h e e l e c t r o n i c c h a r g e g a i n e d i s l o c a l i z e d i n t h e i n t e r c a l a t e l a y e r . O r b i t a l m i x i n g b e t w e e n c a r b o n a n d i n t e r -c a l a t e a t o m s i s g e n e r a l l y n o t o b s e r v e d . A s a c o n s e q u e n c e ( s e e T a b l e 1 . 2 ) , a c c e p t o r G I C s : a r e h i g h l y a n i s o t r o p i c a n d e x h i b i t r e d u c e d c - a x i s c o n d u c t i v i t y c o m p a r e d t o g r a p h i t e . A w i d e v a r i e t y o f s y s t e m s , r a n g i n g f r o m p r o t o n i c a c i d s s u c h a s H o S 0 , , o r L e w i s a c i d s s u c h a s A s F r t o f r e e r a d i c a l s l i k e S 0 o F " , Z 4 0 o h a l o g e n m o l e c u l e s l i k e B r 2 a n d i o n i c . c o m p o u n d s s u c h a s N 0 2 S b F g h a v e b e e n f o u n d t o f o r m a c c e p t o r G T C s o n i n t e r c a l a t i o n . A l t h o u g h a c o m p l e t e c l a s s i f i c a t i o n i s n o t ' a t t e m p t e d , t h e m a j o r 1 8 g r o u p s o f t h e s e c o m p o u n d s a r e d e s c r i b e d i n t h i s s e c t i o n , a n d d e t a i l e d l i s t s o f a c c e p t o r G I C s c a n b e f o u n d i n r e p r e s e n t a t i v e 6 7 r e v i e w a r t i c l e s ' . I . C . 5 S E L E C T E D A C C E P T O R G R A P H I T E I N T E R C A L A T I O N C O M P O U N D S A b r i e f s u m m a r y o f s e l e c t e d i n t e r c a l a t i o n c o m p o u n d s f r o m e a c h m a j o r g r o u p o f a c c e p t o r G I C s i s g i v e n i n t h i s s e c t i o n . H o w e v e r , a n e x h a u s t i v e r e v i e w o f a l l t h e i n t e r c a l a t i o n c o m p o u n d s i n a n y o f t h e s e g r o u p s i s n o t a t t e m p t e d h e r e . ( a ) A C I D S A L T S G r a p h i t e i n t e r c a l a t i o n c o m p o u n d s o f p r o t o n i c a c i d s h a v e b e e n k n o w n t o e x i s t i n t w o c l o s e l y r e l a t e d f o r m s : f i r s t l y a c i d s a l t s o f t h e c o m p o s i t i o n C ^ + X . m H X , w h e r e H X i s a p r o t o n i c a c i d . I n t e r c a l a t i o n c o m p o u n d s o f t h i s t y p e h a v e b e e n p r e p a r e d f r o m s e v e r a l s t r o n g a c i d s i n c l u d i n g ^ S O ^ , H C I O ^ a n d 2 5 H S O g F . T h e y a r e p r e p a r e d b y e l e c t r o c h e m i c a l m e a n s , a n d t h e m e t h o d o f p r e p a r a t i o n h a s c o n t r i b u t e d t o a b e t t e r u n d e r s t a n d i n g o f t h e i n t e r c a l a t i o n p r o c e s s . T h e o c c u p a t i o n o f t h e l a m e l l a r s p a c e s i n a w e l l o r d e r e d m a n n e r d u r i n g t h e i n t e r c a l a t i o n w a s c l e a r l y d e m o n s t r a t e d b y p l o t t i n g t h e e . m . f . o f t h e e l e c t r o -c h e m i c a l o x i d a t i o n a g a i n s t t i m e . T h i s o b s e r v a t i o n w a s m o d i f i e d a n d r e s u l t e d i n t o t h e d e v e l o p m e n t o f c o n c e p t o f s t a g i n g . A s e c o n d t y p e o f a c i d s a l t s a r e f o r m e d i n n o n a q u e o u s s o l v e n t s ( e . g . N i t r o m e t h a n e , p r o p y l e n e c a r b o n a t e ) b y e i t h e r e l e c t r o l y s i n g s a l t s s u c h a s L i C I O , N a B H a n d L i P F u s i n g 1 9 2 6 + g r a p h i t e a n o d e s o r b y o x i d a t i v e i n t e r c a l a t i o n o f N O o r N 0 2 + s a l t s 2 7 ( e . g . N O S b F g , N 0 2 P F g ) . T h e r e s u l t i n g G I C s a r e o f t h e s t o i c h i o m e t r y C * X ~ - m ( s o l v e n t ) , w h e r e X = C l O ^ , B F ^ a n d P F g . T h e d i s t i n c t d i f f e r e n c e s o f t h e s e t y p e s o f a c i d s a l t s a r e t h r e e f o l d : n e u t r a l a c i d m o l e c u l e s a r e n o t p r e s e n t . I n s t e a d s o l v e n t m o l e c u l e s a r e i n t e r c a l a t e d t o a n a p p r e c i a b l e d e g r e e , a n d o f t e n o n l y h i g h e r s t a g e s a r e o b s e r v e d , f o r e x a m p l e : e l e c t r o l y s i s o f L i P F g d i s s o l v e d i n p r o p y l e n e c a r b o n a t e ( P . C ) , f o r m s a s t a g e 2 c o m p o u n d C ^ g P F g ~ • 4 ( P . C ) a s t h e h i g h e s t c o n c e n -t r a t i o n w h i l e o x i d a t i o n b y N 0 o P F r a n d N 0 P F _ i n n i t r o m e t h a n e 2 6 6 r e s u l t i n s t a g e 2 a n d s t a g e 4- c o m p o u n d s r e s p e c t i v e l y a s t h e 2 7 h i g h e s t c o n c e n t r a t i o n T h e f a c t t h a t a n i o n s p r e s e n t i n g r a p h i t e l a t t i c e s a r e a c c o m p a n i e d e i t h e r b y n e u t r a l a c i d o r s o l v e n t m o l e c u l e s h a s r e s u l t e d i n t h e v i e w t h a t o x i d a t i o n o f g r a p h i t e m a y n o t p r o c e e d b e y o n d C ^ o r p e r h a p s v i a o v e r o x i d a t i o n a n d t h a t 7 2 5 n e u t r a l " s p a c e r s " a r e e s s e n t i a l i n t h e s e G I C s ' . T h e r e a r e s o m e h y p o t h e t i c a l a c i d s a l t s o f t h e c o m p o s i t i o n C p + X ( w h e r e 6 ' 0 s F 6 : X = AsFr , O s F r ) . w h i h d o n o t h a v e n e u t r a l a c i d m o l e c u l e s o  2 8 s o l v e n t s i n t e r c a l a t e d i n t h e s y s t e m . H o w e v e r , t h e c o r r e s p o n d -i n g p r o t o n i c a c i d s a r e n o t k n o w n a s s u c h . ( b ) H A L O G E N A N D I N T E R H A L O G E N C O M P O U N D S B r o m i n e a n d c h l o r i n e a r e t h e o n l y d i a t o m i c m o n o n u c l e a r g h a l o g e n s k n o w n t o i n t e r c a l a t e i n t o g r a p h i t e . I n t e r c a l a t i o n c o m p o u n d s f o r m e d b y b r o m i n e a r e s t a b l e a t r o o m t e m p e r a t u r e i n a n a t m o s p h e r e o f t h e e x c e s s i n t e r c a l a n t v a p o u r s , b u t t h e 2 0 c o m p o u n d s c o n t a i n i n g c h l o r i n e a r e s t a b l e o n l y a t t e m p e r a t u r e s b e l o w 0 ° C . A m o n g t h e i n t e r h a l o g e n c o m p o u n d s , I F ^ h a s b e e n f o u n d t o i n t e r c a l a t e a s I F ^ w i t h p a r t i a l f l u o r i n a t i o n o f t h e 2 9 . g r a p h i t e l a t t i c e . S t a b l e G I C s . . a r e f o r m e d w i t h I B r , I C 1 a n d 3 0 B r C l a t r o o m t e m p e r a t u r e . I t h a s b e e n s u g g e s t e d t h a t t h e i n t e r a t o m i c d i s t a n c e s i n t h e h a l o g e n s a n d i n t e r h a l o g e n s m i g h t d e t e r m i n e t h e i r c a p a b i l i t y t o f o r m i n t e r c a l a t i o n c o m p o u n d s w i t h g r a p h i t e . T h e s t r i k i n g f e a t u r e t h a t l e d t o t h i s s u g g e s t i o n i s t h a t a l l t h e h a l o g e n s a n d i n t e r h a l o g e n s t h a t i n t e r c a l a t e i n t o g r a p h i t e h a v e i n t e r a t o m i c d i s t a n c e s , ° . . . v e r y c l o s e t o 2 . 4 6 A , w h i c h i s t h e d i s t a n c e s e p a r a t i n g a d j a c e n t h e x a g o n s i n g r a p h i t e l a y e r s . G r a p h i t e - Bv^ s y s t e m h a s b e e n t h e m o s t s t u d i e d a m o n g t h e s e c o m p o u n d s . X - r a y d i f f r a c t i o n 3 2 s t u d i e s h a v e i n d i c a t e d t h a t t h e i n t e r c a l a t e d b r o m i n e r e m a i n e d i n t h e m o l e c u l a r f o r m w i t h v i r t u a l l y t h e s a m e i n t e r a t o m i c 2 9 d i s t a n c e a s i n f r e e m o l e c u l e s . A n a t t e m p t t o i n t e r c a l a t e . B r F , - i n t o g r a p h i t e l e d t o i n c o n c l u s i v e r e s u l t s , w h i c h w a s a t t r i b u t e d t o t h e r e d u c t i o n o f B r F , - t o B r F ^ d u r i n g i n t e r c a l a t i o n . ( c ) B I N A R Y E L E M E N T H A L I D E S T h e g r a p h i t e - e l e m e n t h a l i d e s y s t e m s c o n s t i t u t e t h e l a r g e s t s u b - g r o u p a m o n g G I C s . R e s e a r c h e f f o r t s i n v o l v i n g t h e s e c o m p o u n d s h a v e b e e n d i r e c t e d p r i m a r i l y t o w a r d s t h e i r c a t a l y t i c u s e s . W h i l e c h l o r i d e s o f m o r e t h a n 4 5 e l e m e n t s h a v e b e e n i n t e r c a l a t e d v e r y f e w b r o m i d e s a r e k n o w n t o i n t e r -1 7 . . . c a l a t e i n t o g r a p h i t e a n d m e t a l i o d i d e i n t e r c a l a t i o n c o m p o u n d s a p p e a r t o b e s t i l l u n k n o w n . G r a p h i t e - b i n a r y 2 1 e l e m e n t f l u o r i d e s y s t e m s , a l t h o u g h f e w e r i n n u m b e r t h a n t h e c o r r e s p o n d i n g c h l o r i d e s , h a v e b e c o m e v e r y p r o m i n e n t d u e t o t h e i r p o t e n t i a l a p p l i c a t i o n s i n e n e r g y s t o r a g e s y s t e m s . A m o n g t h e s e , t h e G I C s o b t a i n e d b y t h e r e a c t i o n o f A s F j - a n d S b F ^ h a v e a t t r a c t e d a t t e n t i o n d u e t o t h e i r i n c r e a s e d b a s a l p l a n e c o n d u c t i v i t y a s w e l l a s t h e i n t r i g u i n g c h e m i c a l c h a n g e s t h a t a c c o m p a n y t h e i n t e r c a l a t i o n p r o c e s s . A l t h o u g h t h e r e a r e d i f f e r e n c e s i n o p i n i o n r e g a r d i n g t h e e x t e n t o f t h e s e c h e m i c a l c h a n g e s , i t i s n o w g e n e r a l l y a c c e p t e d t h a t b o t h A s F g a n d S b F j -u n d e r g o p a r t i a l r e d u c t i o n u p o n i n t e r c a l a t i o n . A l t h o u g h t h e r e a r e n o s a f e c r i t e r i a t o p r e d i c t w h i c h e l e m e n t a l h a l i d e s w o u l d i n t e r c a l a t e i n t o g r a p h i t e , t h e h a l i d e s w h i c h f o r m G I C s s h o w . . 1 7 , 3 3 - 3 5 s o m e c o m m o n f e a t u r e s : ( i ) F o r a n e l e m e n t i n a p a r t i c u l a r o x i d a t i o n s t a t e , t h e c a p a b i l i t y t o i n t e r c a l a t e , i n c r e a s e s w i t h t h e e l e c t r o -n e g a t i v i t y o f t h e h a l i d e a s p o i n t e d o u t a l r e a d y . C i i ) M o s t e l e m e n t h a l i d e s t h a t i n t e r c a l a t e i n t o g r a p h i t e c a n b e r e g a r d e d a s L e w i s a c i d s , o r e l e c t r o n a c c e p t o r s . S o l i d h a l i d e s w h i c h e x i s t e i t h e r i n l a y e r o r m o l e c u l a r l a t t i c e s w i l l i n t e r c a l a t e m o r e r e a d i l y b e c a u s e o f w e a k l a t t i c e f o r c e s . ( i i i ) S o m e h a l i d e s w h i c h d o n o t i n t e r c a l a t e b y t h e m s e l v e s m a y b e i n t e r c a l a t e d i n t h e p r e s e n c e o f g a s e o u s h a l o g e n s . F o r e x a m p l e , A l B r ^ a n d A l C l ^ i n t e r c a l a t e o n l y i n t h e p r e s e n c e o f B r 2 a n d C l „ ^ r e s p e c t i v e l y . 2 2 ( d ) B I N A R Y E L E M E N T O X I D E S A N D O X Y H A L T D E S T h i s g r o u p c o n s i s t s o f s o m e b i n a r y e l e m e n t o x i d e s a n d o x y h a l i d e s w h i c h d o n o t f i t i n t o t h e o t h e r g r o u p s o f a c c e p t o r c o m p o u n d s , b u t a r e r e l e v e n t t o t h i s s t u d y . B i n a r y e l e m e n t o x i d e s s u c h a s S O ^ a n d C r O ^ h a v e b e e n i n t e r c a l a t e d t o f o r m 1 7 3 4 C 7 S 0 3 a n d C g g C r O ^ r e s p e c t i v e l y ' . H o w e v e r , o x i d e s s u c h a s S C ^ , N O a n d N 0 2 d o n o t i n t e r c a l a t e . S o m e o x y h a l i d e s s u c h a s 0 ^ 2 * 3 1 2 a n d M o O C l ^ h a v e a l s o b e e n s u c c e s s f u l l y i n t e r c a l a t e d 3 4 i n t o g r a p h i t e I . D . S T A G I N G P H E N O M E N O N A s m e n t i o n e d e a r l i e r i n s e c t i o n I . B , t h e p r e s e n c e o f w e a k i n t e r l a y e r a t t r a c t i o n i n g r a p h i t e p e r m i t s t h e f o r m a t i o n o f i n t e r c a l a t i o n c o m p o u n d s w i t h t h e l a y e r s o f i n t e r c a l a t e s t a c k e d i n b e t w e e n c a r b o n l a y e r s . T h e m o s t r e m a r k a b l e p h e n o m e n o n i s t h e o r d e r e d s e q u e n c e i n w h i c h c a r b o n a n d . , i n t e r -c a l a t e l a y e r s a r e s t a c k e d a l o n g t h e c - a x i s d i r e c t i o n . T h i s p e r i o d i c i t y i n s t a c k i n g o b s e r v e d b o t h i n d o n o r a n d a c c e p t o r c o m p o u n d s i s r e f e r r e d t o a s t h e s t a g i n g p h e n o m e n o n . F i g . ( 1 . 4 ) i l l u s t r a t e s t h e s t a c k i n g s e q u e n c e e n c o u n t e r e d i n i n t e r c a l a t i o n c o m p o u n d s a t v a r i o u s c o n c e n t r a t i o n s o f t h e i n t e r c a l a t e . T h i s t y p e o f p e r i o d i c a r r a n g e m e n t f o r v a r i o u s c o m p o s i t i o n s i s s u p p o r t e d b y X - r a y d i f f r a c t o g r a m s o f t h e s e s a m p l e s w h i c h a r e . d o m i n a t e d b y ( 0 0 £ ) r e f l e c t i o n s . D u e t o t h e i r o r d e r e d a r r a n g e -m e n t a l o n g t h e c - a x i s , t h e i n t e r c a l a t i o n c o m p o u n d s c a n b e c h a r a c t e r i z e d b y t h e i r l a y e r s t o i c h i o m e t r y , c a l l e d t h e " s t a g e i n d e x " o f t h e s a m p l e . T h e s t a g e i n d e x , n , o f a G I C i n d i c a t e s 23 STAGE 1 STAGE 2 STAGE 3 STAGE 4 A A A A ~ ~ ~ A — - A A A • " B B B A a > g i , A a t x i j. A — ~ B . R ~ ~ « A B • M B ~ * — • A carbon layer Intercalate layer F I G . 1 . 4 STAGING PHENOMENON IN G R A P H I T E I N T E R C A L A T I O N COMPOUNDS 2 4 t h a t t h e r e a r e n c a r b o n l a y e r s s e p a r a t i n g a n y t w o o f t h e c l o s e s t i n t e r c a l a t e l a y e r s i n t h a t p a r t i c u l a r c o m p o u n d ( s e e F i g . 1 . 4 ) . A l s o t h e X - r a y d i f f r a c t o g r a m o f t h a t c o m p o u n d w o u l d s h o w t h e h i g h e s t i n t e n s i t y f o r t h e r e f l e c t i o n d u e t o t h e £ 0 0 ( n + l ) ] p l a n e s . T h e s t a g e i n d e x d o e s n o t d e p e n d o n t h e a r r a n g e m e n t o f t h e i n t e r c a l a t e m o l e c u l e s w i t h i n t h e i n t e r c a l a t e l a y e r , o r t h e e x t e n t o f c h a r g e t r a n s f e r i n v o l v e d ; i t s i m p l y r e f l e c t s t h e e x t e n t t o w h i c h t h e g a l l e r i e s a r e o c c u p i e d . T h e i n t e r c a l a t i o n p r o c e s s l e a d s t o s o m e o r d e r i n g i n t h e c a r b o n l a y e r s a s w e l l . T h e c a r b o n l a y e r s a d j a c e n t t o a n i n t e r c a l a t e l a y e r a r e t e r m e d " b o u n d i n g l a y e r s " a n d t h e o t h e r s a r e c a l l e d " i n t e r i o r l a y e r s " . T h e s e i n t e r i o r l a y e r s , a r e f o u n d i n c o m p o u n d s o f s t a g e > 2 s t a c k e d i n t h e h e x a g o n a l ( A B A B . . . . l a y e r s e q u e n c e ) a r r a n g e m e n t , j u s t l i k e i n p r i s t i n e h e x a g o n a l g r a p h i t e . T h e i n t e r n u c l e a r d i s t a n c e b e t w e e n i n t e r i o r l a y e r s 3 6 a l s o r e m a i n e s s e n t i a l l y t h e s a m e a s i n g r a p h i t e . T h e a r r a n g e -m e n t o f t h e b o u n d i n g c a r b o n l a y e r s i n s o m e G I C s ( f o r e . g . C g K , C g R b . ) i s f o u n d i n ( A A A . . . . ) s e q u e n c e , w h i l e t h e a r r a n g e m e n t ( A B A B ) i s f o u n d i n a n u m b e r o f a c c e p t o r c o m p o u n d s s u c h a s g r a p h i t e - S b F g a n d g r a p h i t e - H N O g , e s p e c i a l l y f o r s t a g e s 2 o r h i g h e r . H o w e v e r t h e r e a r e s e v e r a l G I C s f o r w h i c h t h e a r r a n g e -m e n t o f b o u n d i n g c a r b o n l a y e r s f a l l i n t o a m i x t u r e o f b o t h 7 s e q u e n c e s . C l o s e l y r e l a t e d t o s t a g i n g i s t h e r e p e a t d i s t a n c e , I o f t h e i n t e r c a l a t e l a y e r s a l o n g t h e c - a x i s . T h e r e p e a t d i s t a n c e I i n a s t a g e n i n t e r c a l a t i o n c o m p o u n d c a n b e e x p r e s s e d b y : 25 I c = I g + C n - l ) t e o ( 1 . 1 ) w h e r e I = s e p a r a t i o n o f t w o b o u n d i n g c a r b o n l a y e r s w i t h a n i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m a n d c . = i n t e r l a y e r s e p a r a t i o n i n p r i s t i n e g r a p h i t e . S t a g i n g e x t e n d s t o v e r y l o w i n t e r c a l a t e c o n c e n t r a t i o n s , 7 a n d c o m p o u n d s o f s t a g e t e n h a v e b e e n p r e p a r e d a n d c h a r a c t e r i z e d . T h e l o n g r a n g e e f f e c t s w h i c h c o n t r i b u t e t o s t a g i n g e v e n a t v e r y l o w c o n c e n t r a t i o n s h a v e b e e n a t o p i c o f i n t e r e s t f o r 3 7 - 3 9 t h e o r e t i c a l s t u d i e s . T h e s e s t u d i e s h a v e s h o w n t h a t t h e t o t a l e n e r g y o f t h e s y s t e m w o u l d d e c r e a s e w i t h i n c r e a s e d s t a g e i n d e x a n d t h i s l o w e r e n e r g y i s a m a j o r c o n t r i b u t o r f o r s t a b i l i z i n g t h e h i g h e r s t a g e c o m p o u n d s i n t h e p e r i o d i c s t r u c -2 5 t u r e s . T h e e l e c t r o c h e m i c a l i n t e r c a l a t i o n r e a c t i o n s c l e a r l y s h o w t h a t a n i n c r e a s e d p o t e n t i a l i s r e q u i r e d t o c o n t i n u e t h e i n t e r c a l a t i o n a f t e r a p a r t i c u l a r s t a g e i s r e a c h e d . T h i s a g a i n r e f l e c t s t h e f a c t t h a t h i g h e r s t a g e s t r u c t u r e s h a v e l o w e r e n e r g y . a n d , a s s u g g e s t e d b y t h e t h e o r e t i c a l s t u d i e s , \ t h e o r d e r e d a r r a n g e m e n t o f c a r b o n a n d i n t e r c a l a t e l a y e r s m i g h t p l a y a n i m p o r t a n t r o l e i n d e c r e a s i n g t h e e n e r g y o f t h e s e c o m p o u n d s . T h e o r e t i c a l l y o n e s h o u l d b e a b l e , t o p r e p a r e c o m p o u n d s w i t h a n i d e a l s t r u c t u r e a s s h o w n i n F i g . 1 . 4 . H o w e v e r i n p r a c t i c e , a s a m p l e o f a p a r t i c u l a r s t a g e n m a y n o t h a v e a l l t h e i n t e r c a l a t e s a r r a n g e d i n l a y e r s n e x t t o e v e r y n t h c a r b o n l a y e r a l o n g t h e c - a x i s , i n s t e a d i t m a y a l s . o h a v e s o m e o f t h e i n t e r c a l a t e m o l e c u l e s s p r e a d o u t s i d e t h e s e l a y e r s . T h i s s i t u a t i o n s e e m s t o b e m o r e l i k e l y i n s a m p l e s ' m a d e f r o m 2 6 g r a p h i t e p l a t e s , w h e r e t h e m a c r o s c o p i c d i s t r i b u t i o n o f t h e i n t e r c a l a t e m a y e a s i l y c o n s t i t u t e a m i x t u r e o f s e v e r a l s t a g e s . T o a c c o m o d a t e t h e m a c r o s c o p i c d i s t r i b u t i o n o f t h e i n t e r c a l a t e , 4- 0 D a u m a s a n d H e r o l d p r o p o s e d a d o m a i n ( o r p l e a t e d l a y e r ) m o d e l f o r t h e s t a c k i n g s e q u e n c e i n G I C s . F i g . 1 . 5 i l l u s t r a t e s t h e a r r a n g e m e n t o f c a r b o n a n d i n t e r c a l a t e l a y e r s i n c o m p o u n d s o f s t a g e s 1 , 2 a n d 3 a s p r o p o s e d b y t h i s m o d e l . T h i s m o d e l i s b a s e d o n t h e a s s u m p t i o n t h a t a l l l a m e l l a r s p a c e s a r e f i l l e d e q u a l l y b u t n o t c o n t i n u o u s l y d u r i n g i n t e r c a l a t i o n . T h i s t y p e o f n o n - c o n t i n u o u s o c c u p a t i o n o f a l l g a l l e r i e s l e a d s t o f o r m a t i o n o f i n t e r c a l a t e i s l a n d s i n s t e a d o f c o n t i n u o u s l a y e r s . T h e r a t i o n a l e f o r t h e f o r m a t i o n o f i n t e r c a l a t e i s l a n d s h a s b e e n 3 7 3 8 t h e s u b j e c t o f t h e o r e t i c a l s t u d i e s ' b y S a f r a n a n d H a m a n n , w h i c h s u g g e s t t h a t i n t e r c a l a t e a t o m s o r m o l e c u l e s b e t w e e n t h e s a m e t w o c a r b o n l a y e r s w i l l a t t r a c t o n e a n o t h e r t o f o r m t w o d i m e n s i o n a l i s l a n d s w h i l e t h o s e b e t w e e n d i f f e r e n t p a i r s o f c a r b o n l a y e r s w i l l r e p e l e a c h o t h e r . T h e r e s u l t w o u l d b e t h e f o r m a t i o n o f d o m a i n s o f i n t e r c a l a t e s w i t h m a c r o s c o p i c s i z e s ° 8 s o m e t i m e s e x c e e d i n g 4 0 0 A . T h e a r r a n g e m e n t o f t h e s e d o m a i n s a l o n g t h e c - a x i s l e a d s t o s t a g i n g , a n d t h e e x i s t e n c e o f m i x e d s t a g e s c a n b e a t t r i b u t e d t o t h e e x i s t e n c e o f a m i x t u r e o f d o m a i n s , e a c h o f t h e m p u r e l y s t a g e d . T h i s w o u l d a l s o e x p l a i n t h e m i x e d a r r a n g e m e n t o f c a r b o n l a y e r s p r e s e n t i n s o m e o f t h e G I C s . T h i s m o d e l c a n b e u s e d t o e x p l a i n t h e c o n v e r s i o n o f a s t a g e n c o m p o u n d t o s t a g e ( n - 1 ) d u r i n g c o n t i n u o u s i n t e r -c a l a t i o n , o r t o s t a g e ( n + 1 ) b y t h e r m a l d e c o m p o s i t i o n . I n b o t h c a s e s , t h e s t a g e t r a n s f o r m a t i o n c a n e a s i l y b e e x p l a i n e d b y 27 STAGE 1 STAGE 2 T z z C A R B O N L A Y E R I N T E R C A L A T E L A Y E R STAGE 3 z__z F I G . 1 . 5 T H E D A U M A S - H E R O L D M O D E L O F S T A G I N G 2 8 c o n s i d e r i n g t h e i n t e r c h a n g e o f i n t e r c a l a t e d o m a i n s a s s h o w n i n F i g . 1 . 6 . R a t h e r c o n v i n c i n g e v i d e n c e f o r D a u m a s a n d H a r o l d 4 1 m o d e l w a s f o u n d m t h e e l e c t r o n m i c r o s c o p e p h o t o g r a p h s o f t h e g r a p h i t e - F e C l ^ s y s t e m w h i c h c l e a r l y s h o w e d t h e e x i s t e n c e o f t w i s t e d c a r b o n l a y e r s i n t h e s e c o m p o u n d s , w h i c h a r e t h e b a s i c r e q u i r e m e n t s f o r t h e e x i s t e n c e o f i n t e r c a l a t e i s l a n d s b e t w e e n t h e m . I . E S Y N T H E S I S O F G R A P H I T E I N T E R C A L A T I O N C O M P O U N D S T h e p r i n c i p a l r o u t e t o s y n t h e s i z e G I C s i s t h e d i r e c t i n t e r c a l a t i o n b y e x p o s u r e o f g r a p h i t e t o g a s e o u s , l i q u i d o r d i s s o l v e d i n t e r c a l a n t . T h e r e a r e t w o m a j o r v a r i a b l e s i n t h e s y n t h e s i s o f G I C s . T h e f i r s t v a r i a b l e i s t h e c o n c e n t r a t i o n o f t h e i n t e r c a l a n t w h i c h a s d e s c r i b e d e a r l i e r i n s e c t i o n I . D , l e a d s t o a w e l l o r d e r e d s t a c k i n g p e r i o d i c i t y , t e r m e d s t a g i n g , o f c a r b o n a n d i n t e r c a l a t e l a y e r s , a n d a l l o w s o n e t o v a r y t h e i n t e r l a y e r d i s t a n c e s . T h e o t h e r v a r i a b l e i s t h e s t r e n g t h o f i n t e r a c t i o n b e t w e e n t h e h o s t a n d t h e g u e s t s p e c i e s . T h e s e i n t e r a c t i o n s m a y i n c l u d e : ( i ) o r b i t a l m i x i n g b e t w e e n c a r b o n a n d i n t e r c a l a t e l a y e r s a s o b s e r v e d i n m o s t g r a p h i t e - a l k a l i m e t a l c o m p o u n d s , o r ( i i ) e l e c t r o n t r a n s f e r b e t w e e n g r a p h i t e a n d i n t e r c a l a t e . T h e T a t t e r i s e x p r e s s e d i n t e r m s o f t h e c h a r g e t r a n s f e r f a c t o r f , w h i c h , i s d e f i n e d a s t h e f r a c t i o n o f a n e l e c t r o n c h a r g e l o s t o r g a i n e d p e r i n t e r c a l a t e a t o m o r 2 4 . . m o l e c u l e . F o r e x a m p l e t h e i n t e r c a l a t i o n c o m p o u n d C ^ H S O ~ • 2 H 9 S 0 U f o r m e d b y e l e c t r o c h e m i c a l i n t e r c a l a t i o n o f 29 STAGE 3 STAGE 4 F I G . 1.6 I N T E R C H A N G E O F D O M A I N S O F S T A G E 3 A N D S T A G E 4 R E G I O N S A S M I G H T O C C U R D U R I N G A S T A G E T R A N S F O R M A T I O N ( S T A G E T R A N S -F O R M A T I O N I S C O M P L E T E W H E N A L L T H E I N T E R C A L A T E L A Y E R S H A V E M O V E D T O T H E O P P O S I T E S I D E S A S S H O W N I N T H E D I A G R A M ) 3 0 H ^ S O ^ i n t o g r a p h i t e w o u l d h a v e a c h a r g e t r a n s f e r f a c t o r , f = 0 . 3 3 . C o m p o u n d s w i t h a l o w c h a r g e t r a n s f e r f a c t o r s u c h a s C D B r a r e f o u n d t o b e s t a b l e o n l y i n t h e p r e s e n c e o f s u f f i c i e n t o v a p o u r p r e s s u r e . . T h e d i r e c t i o n o f c h a r g e t r a n s f e r d u r i n g i n t e r c a l a t i o n d e t e r m i n e s w h e t h e r t h e c a r b o n a t o m s i n t h e g r a p h i t e l a y e r s a r e o x i d i z e d o r r e d u c e d , w h i c h i n t u r n i s r e f l e c t e d i n t h e c h a n g e s i n p h y s i c a l p r o p e r t i e s s u c h a s a n i s o t r o p y o f t h e r e s u l t i n g i n t e r c a l a t i o n c o m p o u n d . I . E . I S Y N T H E T I C M E T H O D S T O A C C E P T O R C O M P O U N D S S y n t h e s i s o f a c c e p t o r c o m p o u n d s h a s b e e n a c h i e v e d b y a v a r i e t y o f m e t h o d s d e p e n d i n g o n t h e p h y s i c a l a n d c h e m i c a l p r o p e r t i e s o f t h e i n t e r c a l a n t . D i r e c t i n t e r c a l a t i o n u s i n g b u l k r e a g e n t s , w h i c h e x i s t a s g a s e s o r l o w b o i l i n g l i q u i d s a t a m b i e n t t e m p e r a t u r e a n d a t m o s p h e r i c p r e s s u r e , c a n b e c a r r i e d o u t c o n v e n i e n t l y a t r o o m t e m p e r a t u r e b y e x p o s i n g p r i s t i n e g r a p h i t e t o t h e g a s e o u s o r l i q u i d i n t e r c a l a n t w i t h t h e r e a c t i o n u s u a l l y f o l l o w e d b y w e i g h i n g t h e s a m p l e f r o m t i m e t o t i m e . T h e i n t e r c a l a t i o n o f s o l i d m a t e r i a l s s u c h a s F e C l 3 a n d A l C l ^ , o r v i s c o u s l i q u i d s l i k e ' S b ' F j . w i l l i n v o l v e e l e v a t e d t e m p e r a t u r e r e a c t i o n s . A f t e r t h e s a m p l e h a s r e a c h e d t h e r e q u i r e d c o m p o s i t i o n , e x c e s s o f t h e i n t e r c a l a n t c a n b e r e m o v e d b y f i l t r a t i o n , o r v a c u u m d i s t i l l a t i o n . I n s o m e c a s e s ( e . g . C 0 A s F r , C n B r ) s a m p l e s a r e . b e s t s t o r e d w i t h a s m a l l a m o u n t o f b o b e x c e s s i n t e r c a l a n t v a p o u r s r e m a i n i n g , t o p r e v e n t s p o n t a n e o u s d e i n t e r c a l a t i o n . C o m m o n l y t h e i n t e r c a l a t i o n w i l l i n i t i a l l y t a k e p l a c e 3 1 r a p i d l y , ( s e e F i g . 1 . 7 ) u n t i l a c e r t a i n c o m p o s i t i o n i s r e a c h e d w h i c h i s d e p e n d e n t o n t h e p r o p e r t i e s o f t h e i n t e r c a l a n t . T h e r a t e o f r e a c t i o n d e c r e a s e s r a p i d l y a f t e r t h i s c o m p o s i t i o n . I n s o m e c a s e s r e a c t i o n t i m e s o f s e v e r a l d a y s a r e r e q u i r e d b e f o r e a s t a g e 1 c o m p o u n d i s o b t a i n e d . M o r e s p e c i f i c s y n t h e t i c m e t h o d s c o m m o n l y u s e d f o r t h e p r e p a r a t i o n o f a c c e p t o r c o m p o u n d s a r e b r i e f l y s u m m a r i z e d i n t h e s u b s e q u e n t s e c t i o n . D e t a i l s o f t h e s e m e t h o d s a s w e l l a s e x p e r i m e n t a l c o n d i t i o n s c a n 4 2 4 3 b e f o u n d i n t h e r e c e n t a r t i c l e s ' ( a ) T W O - Z O N E V A P O U R T R A N S F E R M E T H O D T h e t w o - z o n e v a p o u r t r a n s f e r m e t h o d w a s d e v e l o p e d b y 4 4 H a r o l d , a n d i s p r i m a r i l y u s e f u l f o r m t e r c a l a n t s w h i c h e x i s t a s s o l i d s o r h i g h b o i l i n g l i q u i d s a t r o o m t e m p e r a t u r e . T h e i n t e r c a l a n t a n d p r i s t i n e g r a p h i t e a r e t a k e n i n t w o s e p a r a t e c h a m b e r s o f a r e a c t o r , ( F i g . 1 . 8 ) w h i c h a r e c o n n e c t e d b y a t u b e . A f t e r e v a c u a t i o n s u f f i c i e n t v a p o u r p r e s s u r e o f t h e i n t e r c a l a n t i s o b t a i n e d i n s i d e t h e r e a c t o r .' b y i n c r e a s i n g t h e t e m p e r a t u r e o f t h e i n t e r c a l a n t c h a m b e r t o T ^ . T h e c h a m b e r c o n t a i n i n g p r i s t i n e g r a p h i t e i s m a i n t a i n e d a t a h i g h e r t e m p e r a t u r e ( T ^ ) t h a n t h e i n t e r c a l a n t c h a m b e r , t o p r e v e n t c o n d e n s a t i o n o f t h e l i q u i d r e a g e n t o n g r a p h i t e . ' T h e t e m p e r a -t u r e s T 1 a n d a r e c h o s e n ; f o r e a c h i n t e r c a l a n t a f t e r s e v e r a l t r i a l s . T h e c o m p o s i t i o n o f t h e r e a c t i o n p r o d u c t i s c o n t r o l l e d b y t h e t e m p e r a t u r e d i f f e r e n c e ( T ^ - T ) a n d t h e r e a c t i o n t i m e . A f t e r a l l o w i n g s u f f i c i e n t t i m e t o r e a c h t h e r e q u i r e d c o m p o s i -t i o n t h e i n t e r c a l a n t c h a m b e r i s q u e n c h e d f i r s t b e f o r e l o w e r i n g 32 F I G . 1 . 7 T H E R A T E O F I N T E R C A L A T I O N O F V A R I O U S S I Z E S O F G R A P H I T E B Y M o C l r V A P O U R N E A R S A T U R A T I O N b ( F R O M R E F E R E N C E 4 8 ) 3 3 T , c Intercalant Graphite F I G . 1 . 8 T H E T W O - Z O N E V A P O U R T R A N S F E R M E T H O D : ? , A N D T 2 I N D I C A T E T H E T E M P E R A T U R E S O F T H E I N T E R C A L A N T A N D G R A P H I T E R E S P E C T I V E L Y 34 t h e t e m p e r a t u r e i n t h e g r a p h i t e , c h a m b e r t o p r e v e n t c o n d e n s a t i o n o f t h e i n t e r c a l a n t o n g r a p h i t e . T h e m a i n d i s a d v a n t a g e o f t h i s m e t h o d i s t h a t , m o n i t o r i n g s a m p l e c o m p o s i t i o n b y g r a v i m e t r y i s n o t p o s s i b l e b e c a u s e t h e s a m p l e c h a m b e r c a n n o t b e s e p a r a t e d f r o m t h e r e a c t o r . A p p r o x i m a t e c o m p o s i t i o n s a r e o f t e n o b t a i n e d b y m e a s u r i n g c h a n g e s 1 i n s a m p l e t h i c k n e s s ( e . g . b y a t r a v e l l i n g m i c r o s c o p e ) , o r b y i n - s i t u X - r a y d i f f r a c t i o n . T h i s m e t h o d h a s 4 5 b e e n a d o p t e d t o i n t e r c a l a t e s o l i d s s u c h a s A l C l ^ a n d F e C l ^ 46 a n d l i q u i d s s u c h a s S b F , -( b ) I S O T H E R M A L V A P O U R T R A N S P O R T M E T H O D T h e i n t e r c a l a t i o n o f g a s e s ( e . g . A s F ^ ) o r l o w b o i l i n g l i q u i d s ( e . g . B r 2 ) c a n b e e f f e c t e d b y a n i s o t h e r m a l v a p o u r t r a n s p o r t m e t h o d . T h i s r e a c t i o n i s o f t e n c a r r i e d o u t a t r o o m t e m p e r a t u r e . T h i s m e t h o d o f f e r s t h e . f o l l o w i n g a d v a n t a g e s : ( i ) I t i s e a s y t o r e m o v e t h e s a m p l e a t a n y s t a g e t o d e t e r -m i n e t h e a p p r o x i m a t e c o m p o s i t i o n b y w e i g h t i n c r e a s e a n d t o m e a s u r e i t s e l e c t r i c a l c o n d u c t i v i t y . T h e r e a r e a l s o 4 8 . d e s i g n s r e p o r t e d , t h a t ^ a l l o w m o n i t o r i n g t h e r e a c t i o n b y p r e s s u r e m e a s u r e m e n t a n d w e i g h t c h a n g e s m e a s u r e d d i r e c t l y a n d c o n t i n u o u s l y . ( i i ) S y n t h e s i s o f h i g h e r s t a g e c o m p o u n d s c a n b e e f f e c t e d e i t h e r b y c o n t r o l l i n g r e a c t i o n t i m e , o r b y r e s t r i c t i n g t h e a m o u n t o f i n t e r c a l a n t b y c o n t r o l l i n g t h e v a p o u r p r e s s u r e . 3 5 ( i i i ) P r o p e r t i e s s u c h a s . e l e c t r i c a l c o n d u c t i v i t y o r p l a s m a r e f l e c t a n c e c a n b e m e a s u r e d d u r i n g t h e p r o g r e s s o f i n t e r c a l a t i o n p r o c e s s , t h e r a t e o f w h i c h c a n b e m a n i p u l a t e d b y t h e p r e s s u r e o f i n t e r c a l a n t v a p o u r s . ( i v ) H i g h e s t c o n c e n t r a t i o n o f t h e i n t e r c a l a n t c a n b e o b t a i n e d b y u s i n g a n i n c r e a s e d , v a p o u r p r e s s u r e a n d a l o n g e r r e a c t i o n t i m e . A m o d i f i e d f o r m o f t h e v a p o u r p h a s e i n t e r c a l a t i o n i s u s e d f o r n o n v o l a t i l e s o l i d s s u c h a s l a n t h a n i d e c h l o r i d e s , L n C l g ? L a n t h a n i d e c h l o r i d e s a r e h e a t e d w i t h A l C l ^ t o f o r m c o m p l e x e s o f t h e f o r m u l a e L n A l ^ C l ^ w h i c h o n i n t e r c a l a t i o n a t 5 0 0 ° C d e c o m p o s e t o r e l e a s e A l C l ^ w h i l e t h e l a n t h a n i d e i n t e r -1 7 c a l a t e s a s L n C l ^ ( c ) D I R E C T I M M E R S I O N I N T H E I N T E R C A L A N T L i q u i d r e a g e n t s c a p a b l e o f o x i d i z i n g g r a p h i t e , . a n d s u f f i c i e n t l y v o l a t i l e i n v a c u o , c a n b e d i s t i l l e d d i r e c t l y o n t o g r a p h i t e . I n t e r c a l a t i o n m a y t h e n t a k e p l a c e a t a s u i t a b l e t e m p e r a t u r e . T h e r a t e a n d e x t e n t o f I n t e r c a l a t i o n c a n b e c o n t r o l l e d v i a t h e f o l l o w i n g t e c h n i q u e s : ( . i } T h e r e a c t i o n r a t e c a n b e c o n t r o l l e d b y m a i n t a i n i n g t h e r e a c t i o n m i x t u r e a t a l o w t e m p e r a t u r e a n d r e m o v i n g t h e e x c e s s i n t e r c a l a n t e i t h e r b y f i l t r a t i o n o r v a c u u m d i s t i l l a t i o n a f t e r s u f f i c i e n t r e a c t i o n t i m e . 3 6 ( i i ) T h e e x t e n t o f i n t e r c a l a t i o n a n d t h e . c o m p o s i t i o n o f t h e p r o d u c t c a n b e c o n t r o l l e d b y u s i n g o n l y a s t o i c h i o m e t r i c a n o u n t o f t h e i n t e r c a l a n t . T h e d i r e c t i m m e r s i o n t e c h n i q u e h a s b e e n a d o p t e d t o 2 8 4 7 i n t e r c a l a t e l i q u i d s s u c h a s ^2^Q^2 a n d H N < ^ 3 ( d ) D I S S O L V E D S O L U T E I N T E R C A L A T I O N I n t e r c a l a t i o n o f s o l i d s o l u t e s d i s s o l v e d i n n o n - a q u e o u s s o l v e n t s i n t o g r a p h i t e i s a v e r y v e r s a t i l e m e t h o d w h i c h h a s r e s u l t e d i n t h e s y n t h e s i s o f s e v e r a l a c c e p t o r c o m p o u n d s . I n t h e s e r e a c t i o n s t h e s o l u t e m a y f u n c t i o n a s a n o x i d i z i n g a g e n t , e . g . C r O g d i s s o l v e d i n p r o t o n i c a c i d s s u c h a s H S O ^ F f a c i l i t a t e s t h e i n t e r c a l a t i o n o f s o l v e n t m o l e c u l e s a n d t h e a n i o n s , . " . 4 9 a c c o r d i n g t o : C r O _ n C + ( x + 1 ) H S O „ F — > - C S 0 o F - x H S 0 o F + H ( 1 . 2 ) 3 n 3 3 M o r e o f t e n t h e s o l u t e a c t s a s a n o x i d a n t a s w e l l a s a n i n t e r c a l a n t . N i t r o n i u m s a l t s o f s t r o n g a c i d s w i l l o x i d i z e g r a p h i t e i n n i t r o m e t h a n e s o l u t i o n s , r e s u l t i n g i n t h e f o r m a t i o n •u-4- n-u 26,50 o f g r a p h i t e s a l t s a c c o r d i n g t o n C + N 0 2 + X " + y C H 3 N 0 2 » C n + X ~ ' y C H 3 N 0 2 + N 0 2 C l . 3 ) w h e r e X = S b F g , P F g a n d B F ^ . T h i s m e t h o d h a s s o m e d i s a d v a n t a g e s h o w e v e r . R e m o v a l o f e x c e s s i n t e r c a l a n t i s c o m m o n l y a c c o m p l i s h e d b y r e p e a t e d w a s h i n g w i t h e x c e s s s o l v e n t , w h i c h o f t e n r e s u l t s 37 i n p a r t i a l l o s s o f t h e i n t e r c a l a t e a s w e l l , a n d a f f o r d s m a t e r i a l s o f u n c e r t a i n c o m p o s i t i o n r e q u i r i n g d e t a i l e d a n d c o m p l e t e c h e m i c a l a n a l y s i s . T h e c o i n t e r c a l a t i o n o f s o l v e n t m o l e c u l e s c a n o f t e n n o t b e a v o i d e d , a n d b i n a r y c o m p o u n d s o f t h e f o r m C + X a r e n o t o b t a i n e d b y t h i s m e t h o d , a n d n i t r o n i u m s a l t s s u c h a s N O ^ B F ^ a n d N C ^ P F g y i e l d o n l y s t a g e 2 c o m p o u n d s 5 0 a t t h e h i g h e s t c o n c e n t r a t i o n . I n a d d i t i o n g r e a t c a r e i n s o l v e n t p u r i f i c a t i o n a n d d r y i n g i s r e q u i r e d t o a v o i d c o m p l i c a -t i o n s . S o m e o f t h e r e s u l t s o b t a i n e d b y d i s s o l v e d s o l u t e i n t e r c a l a t i o n a r e r a t h e r p u z z l i n g a n d u n e x p e c t e d . F o r e x a m p l e , a t t e m p t s t o r e a c t g r a p h i t e w i t h , s o l u t i o n s o f m e t a l f l u o r i d e s s u c h a s C u F ^ , B e F 2 a n d N i F 2 i n H S O g F r e s u l t i n t h e i n t e r c a l a -t i o n o f H S O ^ F t o a l i m i t o f s t a g e 2 , w i t h o u t t h e i n t e r c a l a t i o n o f m e t a l f l u o r i d e s , e v e n t h o u g h H S O ^ F b y i t s e l f d o e s n o t i n t e r c a l a t e . H o w e v e r t h e r e a c t i o n o f S b F c d i s s o l v e d i n H S 0 o F , w i t h g r a p h i t e r e s u l t s i n t h e f o r m a t i o n o f t e r n a r y i n t e r c a l a -t i o n c o m p o u n d s o f t h e c o m p o s i t i o n C - , ( H S O ^ F ) ( S b F g ) ^ , w i t h t h e v a l u e o f x d e t e r m i n e d b y t h e c o m p o s i t i o n o f t h e s o l u t i o n . . . 4 2 c o n t a i n i n g t h e i n t e r c a l a n t s ( e ) E L E C T R O C H E M I C A L M E T H O D T h e e l e c t r o l y s i s o f n o n - a q u e o u s e l e c t r o l y t e s u s i n g a 2 5 5 1 g r a p h i t e a n o d e ' , h a s b e e n a d o p t e d t o t h e s y n t h e s i s o f a c i d s a l t s o f g r a p h i t e a n d o t h e r b i n a r y G I C s . A t y p i c a l e l e c t r o l y s i s c e l l i s s h o w n i n F i g . 1 . 9 , w h e r e C - ^ d e n o t e s t h e g r a p h i t e a n o d e . T h e v o l t a g e d r o p b e t w e e n t h e a n o d e C ^ , a n d C 0 ( a n e l e c t r o d e m a d e o f p y r o l y t i c g r a p h i t e ) i s r e c o r d e d 38 ax Voltage Recorder i Electrometer lectrolyte C1&C2 are Graphite Electrodes Rj&R 2 a r e Resistances FIG. 1 . 9 APPARATUS FOR THE PREPARATION OF GICs BY THE ELECTROCHEMICAL METHOD 3 9 c o n t i n u o u s l y . A s t h e i n t e r c a l a t i o n p r o c e e d s a n i o n s o f t h e a c i d a r e i n c o r p o r a t e d i n t o C - ^ a n d t h e v o l t a g e b u i l d s u p w i t h t i m e . W h e n 9 6 % H ^ S O ^ i s u s e d a s e l e c t r o l y t e t h e r e a c t i o n a t 5 1 t h e a n o d e c a n b e e x p r e s s e d b y : : 2 4 C + ( x + 1 ) H . 2 S 0 4 ^ - C ^ H S O ^ - x K ^ S O ^ + 0 . 5 H 2 ( 1 . 4 ) w h e r e x = 2 . 5 I n p r a c t i c e o n e c a n o b s e r v e t h e v o l t a g e r e m a i n i n g c o n s t a n t f o r a f e w m i n u t e s w h e n a s t a g e 2 c o m p o u n d i s f o r m e d , t h e n i t w i l l i n c r e a s e a g a i n u n t i l s t a g e 1 c o m p o s i t i o n i s r e a c h e d . T y p i c a l e x a m p l e s o f t h i s m e t h o d a r e : m e t a l c h l o r i d e s s u c h a s B i C l ^ a n d T e C l ^ w h i c h a r e i n t e r c a l a t e d b y t h e e l e c t r o l y s i s o f t h e i r 1 7 . . . m e l t s , a n d v a r i o u s l i t h i u m s a l t s l i k e L i P F n , L i A s F „ a n d b b L i S b F g w h i c h f o r m c o m p o u n d s o f t h e g e n e r a l c o m p o s i t i o n + — 2 8 C 2 ^ X * 4 ( s o l v e n t ) w h e n e l e c t r o l y z e d i n a p r o t i c d o n o r s o l v e n t s T h i s m e t h o d c a n b e e a s i l y a d o p t e d t o s y n t h e s i z e s a m p l e s o f v a r i o u s s t a g e s , b u t t h e c o i n t e r c a l a t i o n o f n e u t r a l m o l e c u l e s f r o m t h e b u l k i n t e r c a l a n t , o r t h e s o l v e n t m o l e c u l e s , w i t h t h e a n i o n c a n n o t b e a v o i d e d . T h e v a r i a b l e a m o u n t o f n e u t r a l m o l e c u l e s p r e s e n t i n t h e f i n a l s a m p l e c a u s e s d i s c r e p a n c i e s i n t h e d e t e r m i n a t i o n o f t h e a c t u a l s t o i c h i o m e t r y o f t h e i n t e r -c a l a t i o n c o m p o u n d . I n a d d i t i o n t h e o x i d a t i o n s t a t e o f g r a p h i t e i n t h e r e s u l t i n g s a l t s d o e s n o t n o r m a l l y g o b e y o n d C ^ . W h e t h e r t h i s i s d u e t o a l i m i t a t i o n o f t h e e l e c t r o l y s i s 6 7 9 m e t h o d o r w h e t h e r i t r e p r e s e n t s a s f r e q u e n t l y c l a i m e d ' ' t h e t r u e l i m i t t o w h i c h g r a p h i t e c a n b e o x i d i z e d w a s n o t e n t i r e l y 40 c l e a r at the outset of t h i s t h e s i s . I.F ', SELECTED' CHEMICAL REACTIONS' OF ACCEPTOR COMPOUNDS Chemical m o d i f i c a t i o n r e a c t i o n s of acceptor i n t e r c a l a -t i o n compounds may be c l a s s i f i e d as f o l l o w s : ( i ) Decomposition r e a c t i o n s or d e i n t e r c a l a t i o n C i i ) S u b s t i t u t i o n or i n t e r c a l a n t replacement r e a c t i o n s ( i i i ) Oxidation or r eduction r e a c t i o n s of the i n t e r c a l a t e ( i v ) A d d i t i o n r e a c t i o n s of the i n t e r c a l a t e . D e i n t e r c a l a t i o n can he e f f e c t e d by heating the sample or i n some cases by applying a dynamic vacuum. D e i n t e r c a l a -t i o n w i l l lead to a residue compound a f t e r which there w i l l be only a n e g l i g i b l e amount of desorption of the i n t e r c a l a n t . S u b s t i t u t i o n of an acceptor I n t e r c a l a t e , termed "double 2 5 decomposition" was f i r s t reported f o r a c i d s a l t s , where the i n t e r c a l a t e d anion:was replaced by washing w i t h excess of a stronger p r o t o n i c a c i d , e.g.: C 2 + 4HS0 4 _ +•• HC10 4 — C^CIOZ + H 2S0 4 (1. The above r e a c t i o n i s the only complete i n t e r c a l a t e exchange r e a c t i o n r e p o r t e d , however the f i n a l product contains n e u t r a l a c i d molecules as w e l l . Reactions of t h i s type have remained r a t h e r r a r e , because most of the acceptor i n t e r c a l a t e s cannot be replaced e a s i l y and c l e a n l y and equi-l i b r i u m mixtures would confuse the s i t u a t i o n and impede a 4 1 p r o p e r i n t e r p r e t a t i o n . T o q u o t e a n e x a m p l e , t h e s u c c e s s i v e t r e a t m e n t o f g r a p h i t e f i r s t w i t h A s F 5 a n d t h e n w i t h N 0 2 S b F g d i s s o l v e d i n n i t r o m e t h a n e h a s r e s u l t e d i n a r a t h e r c o m p l e x m i x t u r e o f S b F g , S b F j . , A s F g , A s F < - a n d A s F ^ i n t e r c a l a t e d i n 5 2 t h e f i n a l p r o d u c t S t u d i e s o n g r a p h i t e - F e C l ^ h a v e s h o w n t h a t i n t e r c a l a t e d 5 3 F e C l ^ c a n b e r e d u c e d t o F e C l ^ b y t r e a t m e n t w i t h H £ a t 3 7 5 ° C , 1 7 o r c o n v e r t e d t o Te^O^- b y h e a t i n g m a s t r e a m o f 0 ^ g S e v e r a l a t t e m p t s h a v e b e e n m a d e a t a c o m p l e t e r e d u c t i o n o f i n t e r c a l a t e d m e t a l h a l i d e s t o m e t a l w i t h a v i e w t o f o r m i n g p o t e n t i a l c a t a l y s t s t e r m e d " m e t a l g r a p h i t e s " . B u t i n n o n e o f t h e s e a t t e m p t s h a s t h e f o r m a t i o n o f a p u r e t r a n s i t i o n m e t a l G I C b e e n e s t a b l i s h e d . T h e s y n t h e s i s a s w e l l a s t h e i n v e s t i g a t i o n s o f t h e p r o p e r t i e s o f a c c e p t o r c o m p o u n d s d e s c r i b e d i n t h i s t h e s i s i : i n v o l v e s s e v e r a l r e a c t i o n s o f a c c e p t o r G I C s , t h e r e f o r e f u r t h e r e x a m p l e s a r e d e s c r i b e d i n t h e a p p r o p r i a t e c h a p t e r s . I . G M E C H A N I S M O F I N T E R C A L A T I O N S e v e r a l i n - s i t u s t u d i e s o f i n t e r c a l a t i o n r e a c t i o n s h a v e b e e n c a r r i e d o u t t o g a i n a b e t t e r u n d e r s t a n d i n g o f t h e 4 8 5 4 m e c h a n i s m o f t h e i n t e r c a l a t i o n p r o c e s s . A c c o r d i n g t o H o o l e y ' w h o i n v e s t i g a t e d t h e g r a p h i t e - B r 2 s y s t e m , t h e i n t e r c a l a t i o n i s i n i t i a t e d b y b a s a l p l a n e a d s o r p t i o n o f t h e i n t e r c a l a n t f o l l o w e d b y i n t e r c a l a t i o n p r o g r e s s i n g f r o m t h i s s i t e . N o e v i d e n c e o f b r o m i n e u p t a k e w a s o b s e r v e d w h e n t h e b a s a l p l a n e s o f t h e h o s t m a t e r i a l w e r e c o v e r e d b y a n i m p e r v i o u s m a t e r i a l . 42 Ubbolo.hde pointed' out the. existence of a th r e s h o l d vapour pressure to i n i t i a t e the i n t e r c a l a t i o n , probably r e q u i r e d to unpin the l a t t i c e d i s l o c a t i o n s , and to r e l i e v e the l a t t i c e s t r a i n during the changes i n atomic s t a c k i n g that take place as the i n t e r c a l a t i o n proceeds. The th r e s h o l d pressure was 54 determined to be dependent on the nature of the i n t e r c a l a n t , the temperature and the type of host graphite chosen. Although the i n t e r c a l a t i o n i s i n i t i a t e d at the edges of the graphite c r y s t a l , even at very low concentrations the compounds have been found to contain a f a i r l y uniform d i s t r i b u -t i o n of the i n t e r c a l a t e i n the g a l l e r i e s of the host gr a p h i t e . 56 Samples of graphite - FeClg have been shown by k i n e t i c s t u d i e s to contain a uniform macroscopic d i s t r i b u t i o n of the i n t e r -c a l a t e even at about 2 0 to 3 0% of the maximum conc e n t r a t i o n . This phenomenon has been i n t e r p r e t e d by co n s i d e r i n g the •formation of i n t e r c a l a t e i s l a n d s In the g a l l e r i e s as soon as the n u c l e a t i o n of the process takes place on the edges of the c r y s t a l . These i n t e r c a l a t e i s l a n d s represent a d i s t r i b u t i o n of the i n t e r c a l a t e molecules or ions s i m i l a r to that found i n 7 stage 1 i n t e r c a l a t i o n compounds . A c t i v a t i o n energy data on the same system supports the view t h a t the i n t e r c a l a t e can d i f f u s e i n t o the g a l l e r i e s at a much higher r a t e than the 5 6 n u c l e a t i o n on the edges. An energy of 1.0.5" kJ/mole I s -re q u i r e d to i n i t i a t e the i n t e r c a l a t i o n of FeCl^ on the edges of a graphite c r y s t a l , but an energy of the order of 8.4-12.6 k J / 5 7 mole would be s u f f i c i e n t to d i f f u s e i t i n t o the g a l l e r i e s . Th.e higher a c t i v a t i o n energy .required f o r the i n t e r c a l a t i o n 4 3 s t e p c a n b e a t t r i b u t e d t o t h e w o r k f u n c t i o n r e q u i r e d t o o v e r c o m e t h e w e a k i n t e r l a y e r a t t r a c t i o n p r e s e n t i n g r a p h i t e , a n d t o f o r m a n o r d e r e d a r r a n g e m e n t o f t h e i n t e r c a l a t e l a y e r s i n t h e a v a i l a b l e l a m e l l a r s p a c e s . I . H . D E N S I T Y O F " S T A T E S : B A N D M O D E L T h e e l e c t r o n i c d e n s i t y o f s t a t e s f o r g r a p h i t e i s i m p o r t a n t i n d e t e r m i n i n g e l e c t r i c a l c o n d u c t a n c e . T h e e n e r g y b a n d s t r u c t u r e o f a n i s o l a t e d c a r b o n l a y e r m a y b e d e s c r i b e d i n t h e f o l l o w i n g w a y s : T h e a o r b i t a l s o f c a r b o n a t o m s f o r m b o n d i n g a n d a n t i b o n d i n g b a n d s w i t h a l a r g e b a n d s e p a r a t i o n o r g a p b e t w e e n t h e m . T h e b o n d i n g a n d a n t i b o n d i n g T T b a n d s o v e r l a p w i t h e a c h o t h e r a s s h o w n i n F i g . 1 . 1 0 , f o r a s i n g l e l a y e r o f c a r b o n a t o m s . I n a t h r e e ' d i m e n s i o n a l m o d e l t h i s o v e r l a p o f 1 3 T T a n d i r * " b a n d s h a s b e e n c a l c u l a t e d t o b e a b o u t 3 0 - 4 0 m e V T h i s r e s u l t s i n e l e c t r o n s f r o m v a l e n c e C i r ) b a n d m o v i n g i n t o t h e c o n d u c t i o n Cir*) b a n d , l e a v i n g p o s i t i v e h o l e s i n t h e v a l e n c e b a n d . B o t h , t h e e l e c t r o n s i n t h e c o n d u c t i o n b a n d , a n d t h e h o l e s i n t h e v a l e n c e b a n d f u n c t i o n a s c a r r i e r s i n p r i s t i n e g r a p h i t e . T h i s t y p e o f 2 D - m o d e l i g n o r e s a n y I n t e r l a y e r i n t e r a c t i o n s . H o w e v e r t h e s e i n t e r a c t i o n s a r e r a t h e r w e a k i n p a r t i c u l a r , i n i n t e r c a l a t i o n c o m p o u n d s , w i t h t h e i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n c a r b o n l a y e r s t e n d i n g t o s h i e l d t h e c a r b o n l a y e r s f r o m e a c h o t h e r . H e n c e t h e 2 D - m o d e l a l t h o u g h n o t " i d e a l " i s a d e q u a t e t o e x p l a i n t h e t r a n s p o r t p r o p e r t i e s o f G I C s 8 . I n t e r c a l a t i o n w i l l c h a n g e t h e d e n s i t y o f s t a t e s 44 Pristine Reduced Energy Energy Oxidized F I G . 1 0 D E N S I T Y O F S T A T E S I N P R I S T I N E , R E D U C E D A N D O X I D I Z E D G R A P H I T E A S E X P L A I N E D B Y T H E B A N D M O D E L ( E F = F E R M I L E V E L ) 4 5 d e p e n d i n g o n t h e d o n o r - a c c e p t o r c h a r a c t e r i s t i c s o f t h e i n t e r -c a l a n t . I n t e r c a l a t i o n o f d o n o r m o l e c u l e s i n t o g r a p h i t e w o u l d r e s u l t i n i n c r e a s e d p o p u l a t i o n o f t h e c o n d u c t i o n b a n d . T h e a d d i t i o n a l e l e c t r o n s i n t h e c o n d u c t i o n b a n d c o u l d a c t a s c a r r i e r s p r o d u c i n g i n c r e a s e d c o n d u c t i o n . I n r e a l i t y p a r t o f t h e a d d e d e l e c t r o n s w o u l d c o n t r i b u t e t o i n c r e a s e d i n t e r a c t i o n b e t w e e n t h e d o n o r i n t e r c a l a t e l a y e r a n d t h e n e i g h b o u r i n g c a r b o n l a y e r s i n a m a n n e r a l r e a d y d i s c u s s e d . N e v e r t h e l e s s t h e d o n o r i n t e r c a l a t i o n c o m p o u n d s s h o w i n c r e a s e d e l e c t r i c a l c o n d u c t i v i t y a l o n g t h e b a s a l p l a n e a n d t h e c - a x i s d i r e c t i o n s ( s e e T a b l e 1 . 2 ) . A c c e p t o r i n t e r c a l a t i o n c o m p o u n d s o n t h e o t h e r h a n d , i m p l y t h e l o s s o f e l e c t r o n d e n s i t y f r o m t h e v a l e n c e b a n d . T h e r e s u l t i n g h o l e s a n d t h e i r m o b i l i t y c a u s e m e t a l l i c t r a n s p o r t p r o p e r t i e s i n a c c e p t o r G I C s . T h e a c c e p t o r i n t e r c a l a t e s w o u l d b e c h a r g e d w i t h l o c a l i z e d e l e c t r o n s , a n d t h e r e f o r e s c r e e n t h e a d j a c e n t c a r b o n l a y e r s f r o m e a c h o t h e r a l l o w i n g f o r v e r y l i t t l e o r n o i n t e r a c t i o n a m o n g t h e c a r b o n p l a n e s ; w h i c h e x p l a i n s t h e e x t r e m e t w o d i m e n s i o n a l c h a r a c t e r i s t i c s o f e l e c t r i c a l c o n d u c t i v i t y a n d t h e v e r y h i g h a n i s o t r o p y o b s e r v e d i n t h e s e m a t e r i a l s . T h e t r a n s p o r t p r o p e r t i e s o f t h e a c c e p t o r G I C s a r e d e t e r m i n e d b y t h e d e n s i t y o f t h e p o s i t i v e h o l e s i n t h e v a l e n c e b a n d , w h i c h i s a f u n c t i o n o f t h e c h a r g e t r a n s f e r f r o m g r a p h i t e t o i n t e r c a l a t e , a n d t h e i r m o b i l i t y . I t i s n o w g e n e r a l l y a c c e p t e d t h a t t h e s e c o m p o u n d s h a v e a l o w e r c a r r i e r d e n s i t y t h a n g r a p h i t e , t h e r e f o r e i t s h o u l d b e t h e e n h a n c e d c a r r i e r m o b i l i t y t h a t c o n t r i b u t e s s u b s t a n t i a l l y t o w a r d s t h e i r m u c h * + • 5 8 - 6 0 i n c r e a s e d c o n d u c t i v i t y 46 I . I STRUCTURAL CHARACTERIZATION OF ACCEPTOR INTERCALATION  COMPOUNDS The most d e f i n i t e method of s t r u c t u r a l c h a r a c t e r i z a t i o n would be s i n g l e c r y s t a l X-ray d i f f r a c t i o n a n a l y s i s . I t i s however d i f f i c u l t to ob t a i n s u i t a b l e s i n g l e c r y s t a l s of graphi t e . The usual source i s n a t u r a l graphite and ofte n i m p u r i t i e s and l a t t i c e defects present problems. While i m p u r i t i e s may be removed by a c i d l e a c h i n g as mentioned before, l a t t i c e defects are ofte n c a r r i e d over i n t o the i n t e r c a l a t i o n compounds formed subsequently. In a d d i t i o n microscopic cracking and e x f o l i a t i o n are w e l l recognized phenomena, which accompany the i n t e r c a l a t i o n process and diminish or destroy the q u a l i t y of the s i n g l e c r y s t a l . Due to these problems s i n g l e c r y s t a l X-ray d i f f r a c t i o n has been r e s t r i c t e d to very few. examples. In a d d i t i o n the vast m a j o r i t y of i n t e r c a l a t i o n compounds have been prepared from p o l y c r y s t a l l i n e forms l i k e HOPG or SP1 graphite. Hence s t r u c t u r a l i d e n t i f i c a t i o n has r e l i e d on X-ray powder., d i f f r a c t i o n and a combination of spectroscopic techniques. These techniques w i l l now be summarized. A n a l y t i c a l and s t r u c t u r a l methods to c h a r a c t e r i z e GICs have two general o b j e c t i v e s : (a) To observe and measure the changes in. i n t r a and i n t e r -l a y e r p r o p e r t i e s such as the l a y e r s e p a r a t i o n s , the stage index, the extent of charge t r a n s f e r and the r e s u l t i n g e l e c t r o n i c t r a n s p o r t p r o p e r t i e s . 4 7 ( b ) T o i d e n t i f y t h e . c o m p o s i t i o n o f t h e I n t e r c a l a t e a n d d e d u c e i t s m o l e c u l a r s t r u c t u r e a n d i t s p o s i t i o n i n g i n t h e i n t e r l a y e r s p a c e . X - r a y p o w d e r d i f f r a c t i o n a n d v i b r a t i o n a l s t u d i e s , ( R a m a n a n d I . R . ) t o d e t e r m i n e t h e s t a g e i n d e x a s w e l l a s t h e e f f e c t s o f c h a r g e t r a n s f e r o n t h e i n - p l a c e C - C b o n d s , a r e m o s t f r e q u e n t l y u s e d t o p r o b e i n t o t h e l a y e r s t r u c t u r e . T h e s e a r e c o m p l e m e n t e d b y d e t e r m i n i n g t h e b u l k s t o i c h i o m e t r y b y g r a v i -m e t r y a n d c h e m i c a l a n a l y s e s . T h e C O C H ) r e f l e c t i o n s o b s e r v e d i n X - r a y d i f f r a c t i o n p a t t e r n s o f t h e s a m p l e s p r o v i d e i n f o r m a t i o n o n t h e s t a g e a n d t h e s t a g e p u r i t y i n t h e s a m p l e . T h e i n t e r -l a y e r s e p a r a t i o n i s d e t e r m i n e d b y u s i n g a s m a n y ( 0 0 O r e f l e c -t i o n s a s p o s s i b l e s o t h a t a n a v e r a g e v a l u e c a n b e o b t a i n e d . F o r i n - s i t u s t u d i e s o f p h y s i c a l p r o p e r t i e s , a n a p p r o x i m a t e s t a g e i n d e x o f t h e s a m p l e c a n b e o b t a i n e d b y m e a s u r i n g t h e t h i c k n e s s o f t h e s a m p l e u s i n g a t r a v e l l i n g m i c r o s c o p e a n d u s i n g t h e e x p r e s s i o n : I . . t c , n — x — 3 . 3 5 t c , n O /" n r ^ n = — x — ( 1 . 6 ) f w h e r e n = s t a g e i n d e x o f t h e s a m p l e t a n d t ^ a r e o r i g i n a l a n d f i n a l t h i c k n e s s e s o f t h e s a m p l e r e s p e c t i v e l y . I = 1 + ( n - l ) c ( 1 . 7 ) c , n s o I = s e p a r a t i o n o f t w o c a r b o n l a y e r s w h i c h h a v e a n i n t e r -c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m . 48 T h e s t a g e i n d e x o b t a i n e d i n t h i s m a n n e r i s o n l y a p p r o x i -m a t e , b e c a u s e o f t h e e r r o r s i n t r o d u c e d i n t h i c k n e s s m e a s u r e m e n t s d u e t o m i c r o c r a c k i n g o f t h e s a m p l e a n d e x f o l i a t i o n o n t h e s u r f a c e a n d e d g e s o f t h e s a m p l e . T h e v i s u a l i n s p e c t i o n o r m o r e a c c u r a t e l y r e f l e c t i v i t y s t u d i e s o f t h e G I C s p r o v i d e s a n i n d i c a t i o n a b o u t t h e s t o i c h i o -m e t r y i n s o m e s a m p l e s w h e r e c o l o u r c h a n g e s d u r i n g i n t e r c a l a t i o n a r e p r o m i n e n t . F o r e x a m p l e , i n t h e g r a p h i t e - A s F ^ s y s t e m , t h e 6 1 s t a g e 1 c o m p o u n d i s r e p o r t e d t o b e d a r k b l u e a n d t h e s t a g e 3 c o m p o u n d i s s i l v e r y i n a p p e a r a n c e . H o w e v e r s a m p l e s o f s t a g e 2 o r l o w e r o f m o s t a c c e p t o r G I C s a p p e a r d a r k b l u e a n d c a n n o t b e d i s t i n g u i s h e d b y v i s u a l i n s p e c t i o n . I n t e r c a l a t i o n o f p o t e n t i a l a c c e p t o r s w i l l r e s u l t i n o x i d a t i o n o f t h e g r a p h i t e l a y e r , w i t h t h e i n t e r c a l a t e p r e s e n t i n r e d u c e d f o r m . T h i s r e d o x p r o c e s s i s r a r e l y s t r a i g h t f o r w a r d a n d o b v i o u s , a n d d e t e r m i n a t i o n o f t h e e x a c t s t o i c h i o m e t r y a n d / o r t h e c h a r g e t r a n s f e r f a c t o r f ( w h i c h i s b y n o m e a n s t r i v i a l ) m a y p r o v i d e v a l u a b l e c l u e s . I t s t i l l r e m a i n s n e c e s s a r y t o d e t e r m i n e i f p o s s i b l e t h e e x a c t n a t u r e o f t h e i n t e r c a l a t e a n d t o d e t e r m i n e i t s s t r u c t u r e . B o t h d i r e c t a n d i n d i r e c t m e t h o d s a r e u s e f u l . D i r e c t m e t h o d s i n v o l v e s p e c t r o s c o p i c t e c h n i q u e s s u c h a s N . M . R . , I . R . a n d R a m a n S p e c t r o s c o p y . T h e s e m e t h o d s , i n a d d i t i o n t o i d e n t i f y i n g - t h e i n t e r c a l a t e , c a n a l s o p r o v i d e v a l u a b l e i n f o r m a t i o n a b o u t t h e s t r u c t u r a l c h a n g e s t h e i n t e r c a l a t e h a s u n d e r g o n e . I n o r d e r t o b e u s e f u l i t i s . n e c e s s a r y t h a t s p e c t r o s c o p i c t e c h n i q u e s b e c a p a b l e o f a n a l y z i n g t h e b u l k o f t h e s a m p l e i n s t e a d o f t h e s u r f a c e o r a r e l a t i v e l y 4 9 small zone underneath the surface. A d d i t i o n a l o r i e n t a t i o n problems e x i s t ; f o r samples of acceptor GICs obtained from HOPG p l a t e s , the p r e c i s e o r i e n t a t i o n of the sample wi t h respect to the magnetic f i e l d of the N.M.R. instrument would determine the depth to which the samples are probed, due to 6 2 the very high anisotropy of these samples. Resing et a l . have shown t h a t bulk a n a l y s i s of the acceptor GICs can be obtained by o r i e n t i n g the c-axis p a r a l l e l to the magnetic f i e l d of the instrument. I f the c-axis i s a l i g n e d perpendicular to the magnetic f i e l d only a " s k i n depth" would be analyzed due to s h i e l d i n g of the inner n u c l e i , by the induced eddy cu r r e n t s . I n f r a r e d r e f l e c t i o n and Raman s c a t t e r i n g provide info r m a t i o n about the nature of the i n t e r c a l a t e s , but the v i b r a t i o n a l modes due to the i n t e r c a l a t e s ; are o f t e n unobserv- • a b l e , due to a combination of strong absorption and extensive r e f l e c t i o n of the i n c i d e n t l i g h t by these samples. There are 7 a l i m i t e d number of examples published i n v o l v i n g a d e t a i l e d v i b r a t i o n a l a n a l y s i s of the i n t e r c a l a t e . Due to the l i m i t e d number of d i r e c t methods a v a i l a b l e and the i n t r i n s i c l i m i t a t i o n s of these methods, often t e n s i m e t r i c measurements and thermal decomposition s t u d i e s have been used. Tensimetric measurements are based on the amount of vapours of a second reagent consumed during a q u a l i t a t i v e conversion of a l l i n t e r c a l a t e s . For example the 6 5 i n t e r c a l a t e d GeFg has r e p o r t e d l y been i d e n t i f i e d 1 by the consumption of F„ according t o : 50 C 1 2GeF 5 + \ F 2- C 1 2 :GeF 6 (1.8) The l i m i t a t i o n s of t h i s approach are twofold: F i r s t l y - t h e assumption that only the i n t e r c a l a t e w i l l r e a c t w i t h f l u o r i n e which may be a r a t h e r hazardous assumption, and secondly a 2-d i s c r i m i n a t i o n between. GeF^ and oligomers l i k e Ge2F^Q i s impossible. I t appears then t h a t t h i s approach i s more c o n t r o v e r s i a l and l e s s i n f o r m a t i v e as a complete bulk a n a l y s i s . As has been mentioned, the GIC can also be d e i n t e r c a l a t e d by continuous evacuation or thermal decomposition and the vapours r e l e a s e d be analyzed by I.R. or mass spectrometry. However d e i n t e r c a l a t i o n does not u l t i m a t e l y lead back to graphite but r a t h e r to what are ominously termed "residue compounds" i n d i c a t i v e of i r r e v e r s i b l e changes induced by the i n t e r c a l a t e . In a d d i t i o n d e i n t e r c a l a t i o n may be viewed as a r e d u c t i v e decomposition or r e v e r s a l of the i n i t i a l i n t e r c a l a -t i o n . Hence r e s i d u a l v o l a t i l e s obtained cannot r e a l l y provide good i n f o r m a t i o n . A t y p i c a l example f o r r e v e r s a l of i n i t i a l i n t e r c a l a t i o n during d e i n t e r c a l a t i o n i s found i n graphite - AsF^ system. The i n t e r c a l a t i o n compound obtained by r e a c t i n g 6 3 graphite with AsFg has been c h a r a c t e r i z e d by As - K s h e l l X-ray absorption studies to contain AsFg , AsF,- and AsFg , but the d e i n t e r c a l a t e d gases from t h i s compound contained 61 6 3 p r i m a r i l y A s F 5 . This may be a t t r i b u t e d to the r e v e r s a l of the e q u i l i b r i u m (1.9) i n the graphite - AsF 5 system during d e i n t e r c a l a t i o n . 3AsF r + 2e ===== 2AsF ~ + AsF, (1.9) 5 b o 51 Therefore i t i s e s s e n t i a l that the r e s u l t s of i n d i r e c t methods be complemented by one or' more of the spectroscopic techniques, before making any conclusion regarding the nature of the i n t e r c a l a t e . I . J VIBRATIONAL SPECTRA OF GRAPHITE AND ITS . INTERCALATION  COMPOUNDS Both Raman and I.R. spectrometric a n a l y s i s have been appli e d to study GIC s . There are however serious l i m i t a t i o n s to t h e i r use. Due to absorption as w e l l as r e f l e c t i o n of these m a t e r i a l s , normal geometries (e.g. transmi s s i o n geometry f o r I.R. and a 90° or 180° s c a t t e r i n g geometry f o r Raman) are unsuited. I n f r a r e d spectra are ther e f o r e best recorded i n the r e f l e c t i o n geometry, while Raman spectra are obtained i n the back s c a t t e r i n g geometry. The r e s u l t i n g spectra are ofte n of r e l a t i v e l y poor q u a l i t y . In a d d i t i o n , use of high energy l a s e r s i n Raman studies may I n i t i a t e d e i n t e r c a l a t i o n or i n t e r c a l a t e decomposition. On the other hand the pe n e t r a t i o n depth f o r I.R. r e f l e c t i o n measurements, or l i g h t s c a t t e r i n g o have been reported to be of the order of 10 0 0 A whereas the depth of i n t e r a c t i o n region i n X-ray photoelectron spectroscopy (XPS) or U.V. photoelectron spectroscopy (UPS) i s of the order ° 12 of 5 A . Therefore I.R. r e f l e c t i o n and Raman s c a t t e r i n g have found some l i m i t e d use i n the s t r u c t u r a l studies of GICs. V i b r a t i o n a l spectra obtained on GIC s provide i d e a l l y i n f o r m a t i o n on the graphite l a t t i c e as w e l l as on the i n t e r -c a l a t e . The i n t r a l a y e r bonding i n the carbon l a y e r s of both 52 graphite and GICs. i s much stronger than the i n t e r l a y e r a t t r a c t i o n s . Therefore v i b r a t i o n a l modes of the carbon l a t t i c e i n graphite and i n GICs show strong correspondence. S i m i l a r l y the i n t e r c a l a t e s w i l l r e t a i n by and large t h e i r 7 v i b r a t i o n a l c h a r a c t e r i s t i c s on i n t e r c a l a t i o n . As discussed before, the I n t e r c a l a t i o n of donor or acceptor species would change the e l e c t r o n d e n s i t y of the IT e l e c t r o n system, and hence would a f f e c t the i n t r a planar forces of the carbon l a y e r s r e s u l t i n g i n a f r e q u e n c y f : s h i f t which i s expected to r e f l e c t the extent of e l e c t r o n t r a n s f e r and u l t i m a t e l y the stage and l a y e r arrangement. I . J . I LATTICE MODES (a) LATTICE MODES OF GRAPHITE The three-dimensional graphite c r y s t a l belongs to the space group Dg^, while the i s o l a t e d carbon l a y e r belongs to D 15 p o i n t group . The c o r r e l a t i o n between the v i b r a t i o n a l modes of these two systems i s shown i n F i g . 1.11. The v i b r a t i o n a l modes of the c r y s t a l can be d i v i d e d i n t o in-plane and out of plane atomic displacements, r i g i d l a y e r displacements and the aco u s t i c modes. The d i r e c t i o n s of atomic displacements f o r each of these v i b r a t i o n a l modes are shown i n F i g . 1.12. The band p o s i t i o n s of a l l of these v i b r a t i o n a l modes have been determined experimentally and the reported frequencies are l i s t e d i n Table 1.3. 53 LAYER CRYSTAL D e h D 6 h E l u ( I R ) E 2 g ( R ) t i n Plane ... c , _ ) A tomic Disp lacements B 2 g . B 2 g JOu t of Plane " " * " " - - - - - - . * , I D J A tomic Disp lacements A 2 u (IR) A g u -B 2 9 ) Rigid Layer j Displacements E 2 g ( R ) « 2 u , E l u - ' - ' . . ( A c o u s t i c ) M o d e s E1 l u FIG. 1.11 THE CORRELATION OF THE ZONE CENTER VIBRATIONAL MODES OF GRAPHITE FOR A SINGLE LAYER AND THE 3-DIMENSIONAL CRYSTAL (RAMAN AND IR ACTVITY ARE INDICATED BY (R) - AND (TR)' -RESPECTIVELY) 54 R A M A N A C T I V E L A T T I C E M O D E S E 2 g i E 2 g 2 I N F R A R E D A C T I V E L A T T I C E M O D E S l u A 2 u F I G . 1 . 1 2 R A M A N , A N D I N F R A R E D A C T I V E L A T T I C E M O D E S O F P R I S T I N E G R A P H I T E ( F R O M R E F E R E N C E 7 ) T A B L E 1 . 3 : L A T T I C E V I B R A T I O N A L M O D E S O F G R A P H I T E V I B R A T I O N A L M O D E F R E Q U E N C Y ( c m - 1 ) R E F E R E N C E E 0 , ( R ) 4 2 6 4 2 K 1 E „ - C R ) 1 5 8 2 ± 1 6 6 , 7 3 2 g 2 E n ( I R ) 1 5 8 8 ± 1 5 8 , 6 7 l u A 0 ( I R ) 8 6 8 ± 1 6 4 2 u 5 6 ( b ) L A T T I C E M O D E S O F G R A P H I T E I N T E R C A L A T I O N C O M P O U N D S T h e e f f e c t o f i n t e r c a l a t i o n o n t h e f o r c e c o n s t a n t o f i n - p l a n e C - C v i b r a t i o n s i s r e f l e c t e d p r o m i n e n t l y i n t h e R a m a n a c t i v e E n _ m o d e f o u n d a t 1 5 8 2 c m ^ i n g r a p h i t e . O n i n t e r c a l a -2 g 2 t i o n t h e r e l a t i v e i n t e n s i t y o f t h e E n _ v i b r a t i o n a l m o d e 2 g 2 d r o p s g r a d u a l l y w i t h t h e c o n c o m m i t t a n t a p p e a r a n c e o f a R a m a n b a n d a t h i g h e r w a v e n u m b e r s ( a b o v e 1 6 0 0 c m W h e n t h e s a m p l e r e a c h e s a l a y e r s t o i c h i o m e t r y c o r r e s p o n d i n g t o s t a g e 2, t h e b a n d a t 1 5 8 0 c m ^ d i s a p p e a r s c o m p l e t e l y , w h i l e t h e n e w v i b r a t i o n a l m o d e r e a c h e s i t s m a x i m u m i n t e n s i t y a t s t a g e 1 c o m p o s i t i o n . T h e r e f o r e t h e a p p e a r a n c e o f t w o b a n d s b o t h o f ^ 2 g 2 s y m m e _ , : r ' y f ° r G I C s w i t h a s t a g e i n d e x > 2 i s a t t r i b u t e d t o l a t t i c e v i b r a t i o n s o f t h e b o u n d i n g c a r b o n l a y e r s ( a b o v e 1 6 0 0 c m , a n d o f i n t e r i o r c a r b o n l a y e r s ( a t ^ 1 5 8 0 c m " ' " ) i n t h e s a m e s a m p l e . , W h e n s t a g e 2 c o m p o s i t i o n i s r e a c h e d a l l c a r b o n l a y e r s b e c o m e b o u n d i n g l a y e r s a n d t h e v i b r a t i o n a l m o d e a t 1 5 8 0 c m ^ d i s a p p e a r s . I n t h e h i g h e r s t a g e c o m p o u n d s t h e i n t e r i o r c a r b o n l a y e r s a r e e f f e c t i v e l y s h i e l d e d b y b o u n d i n g l a y e r s f r o m t h e i n t e r c a l a t e s , t h e r e f o r e t h e f o r c e c o n s t a n t s o f C - C v i b r a t i o n s i n i n t e r i o r c a r b o n l a y e r s r e m a i n e s s e n t i a l l y t h e s a m e a s t h a t i n p r i s t i n e g r a p h i t e . T h e s h i f t t o h i g h e r w a v e n u m b e r s o b s e r v e d i n t h e E 0 n 2 g 2 v i b r a t i o n a l m o d e o f b o u n d i n g c a r b o n l a y e r s i s a t t r i b u t e d t o t h e i n t e r a c t i o n o f i n t e r c a l a t e l a y e r s . I t h a s b e e n 6 8 6 9 o b s e r v e d ' t h a t b o t h d o n o r a n d a c c e p t o r c o m p o u n d s e x h i b i t s t a g e d e p e n d e n c e i n i n t e n s i t y a s w e l l a s b a n d p o s i t i o n o f t h e E 2 2 m o d e s o f b o u n d i n g c a r b o n l a y e r s , a n d t h e o r e t i c a l 5 7 7 0 7 1 m o d e l s ' h a v e b e e n , p r o p o s e d t o e x p l a i n t h i s e f f e c t . T h e s t a g e d e p e n d e n c e o f ^2g2 m o d e s ° ^ S O ] T i e d o n o r a n d a c c e p t o r c o m p o u n d s a r e i l l u s t r a t e d I n F i g . 1 . 1 3 . F o r s t a g e 1 a c c e p t o r G I C s , t h e E n 0 m o d e i s o b s e r v e d a t h i g h e r w a v e n u m b e r s , - ~ 2 g 2 s h i f t e d f r o m i t s p o s i t i o n i n p r i s t i n e g r a p h i t e b y 5 0 - 6 0 c m F o r d o n o r G I C s , t h e h i g h e s t f r e q u e n c y o f t h e E « „ m o d e i s o b s e r v e d a t v e r y d i l u t e c o n c e n t r a t i o n s o f t h e i n t e r c a l a t e ( s t a g e i n d e x > 6 ) a n d a s h i f t t o l o w e r w a v e n u m b e r s ( b y ^ 1 0 c m " ' " ) o c c u r s d u r i n g f u r t h e r i n t e r c a l a t i o n . T a b l e 1 . 4 s u m m a r i z e s t h e F 2 g 2 ^ r e c l u e n c y ° f s o m e d o n o r a n d a c c e p t o r G I C S a n d t h e C - C b o n d l e n g t h s o f s o m e o f t h e s e c o m p o u n d s . I n t e r c a l a t i o n o f a c c e p t o r s p e c i e s i s e x p e c t e d t o l o w e r s l i g h t l y t h e b o n d o r d e r o f C - C b o n d s i n t h e b o u n d i n g l a y e r s d u e t o t h e l o s s o f n e l e c t r o n d e n s i t y f r o m b o n d i n g o r b i t a l s t o i n t e r c a l a t e s . B u t a l l a c c e p t o r G I C s s h o w a s h i f t t o h i g h e r w a v e n u m b e r s o f t h e E „ „ v i b r a t i o n a l m o d e l A l t h o u g h v e r y l 2 g 2 l i m i t e d n u m b e r o f d a t a a r e a v a i l a b l e f o r C - C b o n d l e n g t h s i n a c c e p t o r G I C s • a l l o f t h e m e a s u r e d v a l u e s s h o w a d e c r e a s e i n b o n d l e n g t h f r o m t h a t o f g r a p h i t e ( s e e T a b l e 1 . M - ) . T h e s i t u a t i o n s e e m s t o b e m o r e c o m p l i c a t e d f o r d o n o r G I C s . T h e b o n d l e n g t h d a t a a v a i l a b l e f o r d o n o r G I C s s h o w a g r a d u a l i n c r e a s e i n C - C b o n d l e n g t h s w i t h i n c r e a s i n g a m o u n t o f i n t e r c a l a t e , c o n s i s t e n t w i t h t h e o b s e r v e d l o w e r i n g o f t h e f r e q u e n c y o f E 2 g 2 m o d e s i n ^ e R a m a n s p e c t r u m . W h i l e f o r a l l s t a g e 2 c o m p o u n d s C - C b o n d s a r e s l i g h t l y l e n g t h e n e d , s t i l l t h e E 2 g 2 b a n d f ° u n d c m 1 h i g h e r t h a n i n g r a p h i t e . T h e s e c o m p l i c a t i o n s m a y b e d u e t o p a r t i a l o r b i t a l o v e r l a p b e t w e e n 58 1 6 4 0 1630 1620 1610 1600 1590 1 5 8 0 1570 T T h 2 g 2 « MiCl t (300 K ) o F*Clj (300*) • Br 2 ( 7 7 K ) 0 A*F 5 1300 K ) « 1CI (77 K) A A I D , (300 K) A MNOj (300K) • SOClj (300K) • MOPO (300K) 1620 1590 1580 )S70 1/Stoge — i i i i i • Cl(SOOK) ORb(77K) • »(SOOK) • K ( S O O K ) _ • Li (77K) • LI ( S O O K ) • -E'° 2 g 2 >, , i i • J 1 UStoge R E C I P R O C A L S T A G E D E P E N D E N C E : ' O F T H E R A M A N F R E Q U E N C I E S A S S O C I A T E D W I T H T H E G R A P H I T E I N T E R I O R ( E ° ) A N D B O U N D I N G ( E n . ) L A Y E R S Igl 2 g 2 F O R ( A ) A C C E P T O R A N D ( B ) D O N O R G I C s . ( F R O M R E F E R E N C E 7) 5 9 T A B L E . 1 . 4 : I N - P L A N E V I B R A T I O N A L M O D E S A N D C - C B O N D D I S T A N C E S O F G R A P H I T E A N D I T S I N T E R C A L A T I O N C O M P O U N D S M A T E R I A L G r a p h i t e S T A G E ' 2 K 2 F r e q ( c m ) 1 5 8 2 " C - C o ( A ) 1 . 4 2 1 R E F E R E N C E ~2R2 6 6 d C - C 1 5 D O N O R G I C s C „ K C 1 6 K C J b l b C „ C s C - i _ C s 1 6 C c L i b C 1 2 L i 1 2 1 2 1 2 1 2 1 5 0 0 ( b ) 1 5 9 9 1 5 0 0 ( b ) 1 6 0 2 1 5 0 0 ( b ) 1 5 9 8 1 5 9 0 1 6 0 0 1 . 4 3 2 1 . 4 2 6 1 . 4 3 1 1 . 4 3 1 1 . 4 3 5 1 . 4 2 9 6 9 6 9 6 9 6 9 6 9 6 9 6 8 6 8 7 5 7 6 7 5 7 5 7 5 7 5 A C C E P T O R G I C s C . c A s F c 1 b D C 1 1 . 3 N i C 1 2 . 1 3 C 5 . 9 F e C 1 3 C 1 0 H S O 3 F 2 2 1 1 1 6 2 2 1 6 2 7 1 6 4 3 1 . 4 1 8 1 . 4 2 0 1 . 4 1 7 6 9 6 8 7 4 7 7 7 8 7 2 6 0 c a r b o n a n d i n t e r c a l a t e a t o m s . . T h e e l e c t r o n i c e f f e c t s , c o n s i d e r i n g t h e c h a r g e t r a n s f e r w o u l d n o t e x p l a i n t h e s e e f f e c t s . T h e l a t t i c e s t r a i n i n t r o d u c e d b y i n t e r c a l a t e s h a s 7 1 • b e e n c o n s i d e r e d t o h a v e c o n t r i b u t e d t o t h e o b s e r v e d c h a n g e s i n b o n d l e n g t h s a n d b o n d e n e r g i e s o f d o n o r a n d a c c e p t o r G I C s . 7 2 T h e o r e t i c a l m o d e l s c o n s i d e r i n g t h e t o t a l e n e r g y o f t h e s y s t e m d u r i n g c h a r g e t r a n s f e r a r e b a s e d o n t h e a s s u m p t i o n t h a t t h e t r a n s f e r r e d c h a r g e t o c a r b o n l a y e r s i s l o c a l i z e d i n t h e b o u n d i n g l a y e r s w h i l e t h e s t r a i n i s e q u a l l y s h a r e d b y a l l l a y e r s . T h e s e m o d e l s h a v e s h o w n t h a t t h e c h a n g e i n b o n d l e n g t h ( U ) i n t h e b o u n d i n g c a r b o n p l a n e s o f a s t a g e n c o m p o u n d c a n b e e x p r e s s e d b y : U , I N ( A ) = 0 . 1 5 7 f + 0 . 1 4 6 . I f | 3 / 2 + 0 . 2 3 6 f 2 ( 1 . 1 0 ) ( n = 1 ) c 1 c 1 c a n d U r . ; 0 N = - U ' . , ( 1 . 1 1 ) ( n > 2 ) n ( n = l ) w h e r e f d e n o t e s t h e f r a c t i o n o f t h e c h a r g e o f a n e l e c t r o n a c q u i r e d b y e a c h c a r b o n a t o m i n t h e b o u n d i n g l a y e r s d u e t o t h e c h a r g e t r a n s f e r b e t w e e n g r a p h i t e a n d i n t e r c a l a t e . I n p r a c t i c e i t i s f o u n d t h a t E n „ v i b r a t i o n a l m o d e s o f 2 g 2 s t a g e 1 a n d 2 a c c e p t o r G I C s d i f f e r b y 2 0 - 3 * 0 ' • c m , a n d h e n c e t h e f r e q u e n c y o f t h i s m o d e ' i c a n b e u s e d a s a n i n d i c a t o r o f t h e a p p r o x i m a t e s t a g e i n d e x o f t h e i n t e r c a l a t i o n c o m p o u n d s . I n f r a r e d s p e c t r o s c o p y u s i n g F o u r i e r t r a n s f o r m m e t h o d s h a s b e e n u s e d t o s t u d y t h e v i b r a t i o n a l m o d e s o f G I C s . . T h e E - ^ u v i b r a t i o n a l m o d e o f i n t e r i o r c a r b o n l a y e r s i n 6 1 g r a p h i t e - A l C l ^ s a m p l e s , o f s t a g e s 2 t o 8 h a v e b e e n o b s e r v e d a t ^ 1 5 8 8 c m i n c l o s e p r o x i m i t y t o t h e s a m e v i b r a t i o n i n H O P G . T h e E - ^ v i b r a t i o n a l m o d e o f b o u n d i n g g r a p h i t e l a y e r s a r e 7 9 s h i f t e d t o l o w e r w a v e n u m b e r s . H o w e v e r , n o I . R . a c t i v e 7 v i b r a t i o n s a r e o b s e r v e d f o r s t a g e 1 i n t e r c a l a t i o n c o m p o u n d s . I . J . 2 I N T E R C A L A T E V I B R A T I O N S T h e v i b r a t i o n a l m o d e s o f i n t e r c a l a t e s a r e g e n e r a l l y v e r y r a r e l y o b s e r v e d i n t h e R a m a n s p e c t r a o f G I C s . S o m e e x c e p t i o n s w h e r e i n t e r c a l a t e v i b r a t i o n s o f a c c e p t o r G I C s a r e o b s e r v e d , a n d t h e v i b r a t i o n a l m o d e s o f t h e c o r r e s p o n d i n g i n t e r c a l a n t m o l e c u l e s , a r e l i s t e d i n T a b l e 1 . 5 . T h e i n t e r c a l a t e v i b r a t i o n a l m o d e s a r e o f t e n o b s e r v e d a t s l i g h t l y l o w e r w a v e n u m b e r s f r o m t h o s e o f f r e e m o l e c u l e s . T h i s e f f e c t h a s b e e n a t t r i b u t e d t o e i t h e r a r e d u c t i o n i n b o n d s t r e n g t h s o r f o r c e c o n s t a n t u p o n i n t e r c a l a t i o n , o r t h e v i b r a t i o n a l m i x i n g o f t h e i n t e r c a l a t e m o d e s w i t h g r a p h i t e l a t t i c e m o d e s , r e s u l t i n g i n a s h i f t t o l o w e r w a v e n u m b e r s o f t h e f o r m e r a n d t o h i g h e r w a v e n u m b e r s o f t h e l a t t e r . I . K . P U R P O S E O F T H I S W O R K T h e p r e c e d i n g s u r v e y h a d b e e n i n t e n d e d a s a n i n t r o d u c -t i o n i n t o t h e f i e l d o f g r a p h i t e i n t e r c a l a t i o n c o m p o u n d s w i t h p a r t i c u l a r e m p h a s i s o n a c c e p t o r i n t e r c a l a t i o n c o m p o u n d s . A n a t t e m p t w a s m a d e t o r e l a y a c l e a r , t h o u g h p e r h a p s n o t c o m p r e h e n s i v e a n d e x h a u s t i v e , v i e w o f t h e a i m s a n d t h e s c o p e o f c u r r e n t r e s e a r c h i n t h i s f i e l d a s s e e n f r o m a c h e m i s t ' s 6 2 T A B L E 1 . 5 : I N T E R C A L A T E V I B R A T I O N A L M O D E S O F S O M E G I C s G I C S T A G E I N T E R C A L A T E E Q U I V A L E N T R E F E R E N C E M O D E F R E Q . M O D E O F F R E E , - L I N T E R C A L A N T n ( c m } F R E Q . ( c m " 1 ) C B r 2 2 2 4 2 3 2 3 ( g ) 6 9 n 1 5 2 3 0 0 ( s ) 1 0 4 C I B r 2 1 2 3 0 2 6 8 ( g ) 6 9 n 2 0 0 1 1 0 9 6 C . . . I C I ; 1 1 8 6 3 8 4 ( g ) 6 9 n C 1 0 H S O 3 F 1 1 1 5 0 - 1 2 7 0 1 2 3 0 - 1 4 4 5 7 4 1 0 5 0 - 1 0 7 5 1 1 7 8 9 2 0 - 9 6 0 9 6 0 7 9 0 - 8 2 0 8 5 0 63 s t a n d p o i n t . W h i l e g r e a t a c h i e v e m e n t s h a v e b e e n m a d e , p a r t i c u -l a r l y i n t h e l a s t d e c a d e , t o w a r d s a b e t t e r u n d e r s t a n d i n g o f t h i s c l a s s o f c o m p o u n d s , i t s e e m s c l e a r t h a t n o t a l l q u e s t i o n s h a v e b e e n a n s w e r e d , n o t a l l s y s t e m s a r e c o m p l e t e l y u n d e r s t o o d a n d t h a t r o o m s t i l l e x i s t s i n t h i s f i e l d f o r c h e m i c a l r e s e a r c h . O u r i n t e r e s t i s f o u n d o n t w o i n t e r - r e l a t e d a p p r o a c h e s : ( i ) t h e e x p l o r a t i o n o f n e w s y n t h e t i c m e t h o d s t o a c c e p t o r G I C s a n d ( i i ) t h e d e v e l o p m e n t , o f a n a l y t i c a l a n d s p e c t r o s c o p i c m e t h o d s f o r t h e s t u d y o f t h e s e m a t e r i a l s . T h e s y n t h e t i c a t t e m p t s a r e b a s e d o n t h e u s e o f b i s ( f ' l u o r o -s u l f u r y l ) p e r o x i d e , ^ O g F ^ ^ a s a p r i m a r y o x i d a t i v e i n t e r c a l a n t . T h e v e r s a t i l i t y o f t h i s r e a g e n t t o w a r d s t h e s y n t h e s e s o f s e v e r a l t r a n s i t i o n m e t a l f l u o r o s u l f a t e s h a s i n t h e p a s t b e e n e x t e n s i v e l y s t u d i e d i n o u r g r o u p , a n d t h e a d o p t i o n o f s i m i l a r r e a c t i o n s t o l a y e r e d m a t e r i a l s a p p e a r e d t o b e a p l a u s i b l e r o u t e t o n o v e l a c c e p t o r i n t e r c a l a t i o n c o m p o u n d s . A t t h e t i m e o f 2 8 a i n c e p t i o n o f t h i s w o r k o n l y a c o m m u n i c a t i o n b y B a r t l e t t e t a l . o n t h e f o r m a t i o n o f g r a p h i t e f l u o r o s u l f a t e , w i t h a s t a g e 1 c o m p o s i t i o n o f C - ^ S O ^ F b a s e d o n t h e r e a c t i o n o f S 2 0 g F 2 o n g r a p h i t e , h a d b e e n p u b l i s h e d ; h o w e v e r t h e . ^ l i m i t i n g 2 8 b c o m p o s i t i o n w a s l a t e r r e v i s e d t o b e C g S O ^ F . O u r s y n t h e t i c a t t e m p t s b a s e d o n t h e l i q u i d p h a s e r e a c t i o n o f S 2 0 6 F 2 o n H O P G a n d S P 1 g r a p h i t e w e r e c o m p l e m e n t e d b y t h e g a s p h a s e s t u d i e s o f t h e s a m e r e a c t i o n u s i n g v a r i o u s t y p e s a n d p h y s i c a l s h a p e s 64 o f g r a p h i t e , c a r r i e d o u t s i m u l t a n e o u s l y b y P r o f e s s o r J . G . H o o l e y o f t h i s d e p a r t m e n t a n d s o m e o f h i s r e s u l t s h a v e n o w b e e n 8 0 p u b l i s h e d . T h e l i q u i d p h a s e i n t e r c a l a t i o n r e a c t i o n s c a r r i e d 8 1 o u t b y u s e s t a b l i s h e d a l i m i t i n g c o m p o s i t i o n C ^ S O ^ F w i t h n r a n g i n g . f r o m 7 . 0 4 - t o 7 . 5 6 w h i l e g a s p h a s e s t u d i e s b y H o o l e y g s u g g e s t e d C ^ S O ^ F . A l a t e r r e p o r t b y B a r t l e t t e t a l . a l s o s u g g e s t e d C ^ S O ^ F a s t h e l i m i t i n g c o m p o s i t i o n . B a s e d o n t h e l i g a n d r e p l a c e m e n t r e a c t i o n s e s t a b l i s h e d o v e r t h e y e a r s i n o u r g r o u p f o r t h e c o n v e r s i o n o f t r a n s i t i o n m e t a l f l u o r o s u l f a t e s t o n o v e l c o m p o u n d s , t h e c h e m i c a l r e a c t i o n s o f t h e i n t e r c a l a t e d f l u o r o s u l f a t e g r o u p w e r e s e l e c t e d b y u s a s p o t e n t i a l s y n t h e t i c r o u t e s t o n o v e l a c c e p t o r G I C s . M a j o r a d v a n t a g e s o f t h e s e r e a c t i o n s c o u l d b e q u o t e d a s : ( I ) T h e s e l e c t i o n o f " w e l l u n d e r s t o o d " r e a c t i o n s w h i c h g o t o c o m p l e t i o n w i t h o u t f o r m i n g b y p r o d u c t s p o s i n g d i f f i c u l t s e p a r a t i o n p r o b l e m s , a n d r e q u i r e o n l y " m i l d r e a c t i o n c o n d i t i o n s " t o a v o i d e x c e s s i v e s i d e r e a c t i o n s , s e e m e d t o p r o m i s e r a t h e r c e r t a i n s u c c e s s , b a s e d o n t h e l o n g s t a n d i n g r e s e a r c h e x p e r i e n c e o f o u r g r o u p i n t h i s a r e a . T h e i n v e s t i g a t i o n o f t h e i n t e r a c t i o n o f h a l o g e n f l u o r o s u l f a t e s w i t h g r a p h i t e w a s t o b e u n d e r t a k e n d u e t o t h e i r c h a r a c t e r i s t i c s a s o x i d i z i n g a s w e l l a s f l u o r o -s u l f o n a t i n g a g e n t s w h i c h i n t h e p a s t h a v e b e e n s u c c e s s -f u l l y a d o p t e d f o r t h e s y n t h e s e s o f t r a n s i t i o n m e t a l c o m p o u n d s i n o u r r e s e a r c h g r o u p . 65 ( i i ) T h e a v a i l a b i l i t y o f s u i t a b l e p r e c e d e n t s f o r t h e s e r e a c t i o n s s h o u l d h e l p t o e s t a b l i s h a h o p e f u l l y b e t t e r i d e n t i f i c a t i o n o f t h e n a t u r e o f i n t e r c a l a t e d s p e c i e s , u s i n g t h e e x i s t i n g a n a l o g u e s . ( i i i ) T h e f o r m a t i o n o f G I C S w i t h o u t t h e c o i n t e r c a l a t i o n o f s o l v e n t s a n d o t h e r e x t e r n a l r e a g e n t s w a s t o b e a t t e m p t e d t o a c h i e v e r e p r o d u c i b i l i t y i n t h e s e r e a c t i o n s . T h e u s e o f a p p r o p r i a t e t e c h n i q u e s a n d s u i t a b l e e q u i p m e n t t o h a n d l e t h e c o r r o s i v e a n d m o i s t u r e s e n s i t i v e i n t e r c a l a n t s w e r e s e e n a s a n e s s e n t i a l p r e r e q u i s i t e f o r t h i s p u r p o s e . T h e c o m p o s i t i o n o f t h e f i n a l p r o d u c t o f i n t e r c a l a t i o n h a s o f t e n b e e n d e t e r m i n e d o n l y g r a v i m e t r i c a l l y , w h i c h c a n b e r a t h e r a m b i g u o u s . I n m a n y c a s e s n o s e r i o u s a t t e m p t a t a q u a n t i t a t i v e c o m p o s i t i o n d e t e r m i n a t i o n h a s b e e n u n d e r t a k e n . W h i l e c o m p l e t e q u a n t i t a t i v e a n a l y s i s o f n o v e l G I C s d o e s n o t a n s w e r a l l t h e q u e s t i o n s r e g a r d i n g t h e n a t u r e o f t h e i n t e r -c a l a t e a n d t h e e x t e n t o f c h a r g e t r a n s f e r , i t i s i n o u r v i e w a n e c e s s a r y f i r s t s t e p t o w a r d s a b e t t e r u n d e r s t a n d i n g . I n t h e a b s e n c e o f d i r e c t i n f o r m a t i o n f r o m X - r a y s i n g l e c r y s t a l s t u d i e s , s t r u c t u r a l c o n c l u s i o n s a r e l a r g e l y b a s e d o n s u p p o r t i n g p h y s i c a l a n a l y t i c a l t e c h n i q u e s . H o w e v e r d u e t o t h e c o m p l e x n a t u r e o f t h e s e m a t e r i a l s a c o m b i n a t i o n o f s e v e r a l c o m p l e -m e n t a r y t e c h n i q u e s i s n e e d e d , i f t h e i d e n t i t y o f t h e i n t e r -c a l a t e i s t o b e c l e a r l y e s t a b l i s h e d . I n a d d i t i o n a l l t h e s e t e c h n i q u e s h a v e l i m i t a t i o n s , b u t t h e i r c o n c e r t e d u s e r e d u c e s s o m e o f t h e s e l i m i t a t i o n s . 6 6 C o m p l e t e c h e m i c a l a n a l y s e s t o d e t e r m i n e t h e c o m p o s i t i o n w a s s e e n a s a c o r n e r s t o n e o f t h i s s t u d y , t o c h a r a c t e r i z e t h e G I C s . I n t h i s m a t t e r t h e t e c h n i q u e d e v e l o p e d b y B o r d a e t a l . o f t h i s d e p a r t m e n t t o d e t e r m i n e t h e . e a r b o n o c o n t e h t s o f m a t e r i a l s r i c h i n c a r b o n w a s f o u n d t o b e s u i t a b l e a n d 2 8 b r e l a t i v e l y f r e e o f t h e p r o b l e m s u s u a l l y e n c o u n t e r e d i n t h e a n a l y s e s o f G I C s p r o v i d i n g r e s u l t s w i t h a h i g h d e g r e e o f a c c u r a c y . R a m a n a n d I . R . S p e c t r o m e t e r s w e r e r e a d i l y a v a i l a b l e t o o u r r e s e a r c h g r o u p . A s o l i d s t a t e p u l s e d F T - N M R i n s t r u m e n t i n t h i s d e p a r t m e n t w a s a l s o t o b e m a d e a v a i l a b l e o n a p a r t t i m e b a s i s . T h e s e i n s t r u m e n t s w e r e t o b e u s e d w i t h s u i t a b l e m o d i f i c a t i o n s r e q u i r e d t o a n a l y z e G I C s . T h e d e v e l o p m e n t o f t h e s e p h y s i c a l m e t h o d s t o c h a r a c t e r i z e G I C s w a s a n e s s e n t i a l p r e - r e q u i s i t e f o r o u r s t u d i e s . T o d e t e r m i n e t h e i n t e r l a y e r s e p a r a t i o n o f t h e G I C s , a n X - r a y p o w d e r d i f f r a c t o m e t e r w a s t o b e u s e d s i n c e i t w a s a v a i l a b l e t o u s i n t h e d e p a r t m e n t . T h e s t u d y o f e l e c t r i c a l c o n d u c t i v i t y o f t h e i n t e r -c a l a t i o n c o m p o u n d s s y n t h e s i z e d i n t h i s t h e s i s w a s t o b e u n d e r t a k e n w i t h t h e p u r p o s e o f e s t a b l i s h i n g t h e e f f e c t o f t h e n a t u r e a n d p a c k i n g o f t h e i n t e r c a l a t e s o n t h e e l e c t r i c a l c o n d u c t i v i t y o f t h e s e m a t e r i a l s . A n i n v e s t i g a t i o n o f t h e e l e c t r i c a l c o n d u c t i v i t y o f t h e a c c e p t o r G I C s w i t h v a r i o u s d e g r e e s o f c h a r g i n g i n t h e i n t e r c a l a t e l a y e r s w a s e x p e c t e d t o p r o v i d e a b e t t e r i n s i g h t i n t o t h e e f f e c t o f t h e i o n i c s a l t l i m i t o f t h e G I C s o n t h e i r p h y s i c a l p r o p e r t i e s . 67 C H A P T E R I I E X P E R I M E N T A L 6 8 C H A P T E R I I E X P E R I M E N T A L I I . A . G E N E R A L C O M M E N T S T h i s c h a p t e r w i l l d e a l w i t h g e n e r a l e x p e r i m e n t a l t e c h n i q u e s a n d t h e s o u r c e s o f s t a r t i n g m a t e r i a l s u s e d i n t h i s s t u d y ; s p e c i f i c s y n t h e s e s w i l l b e d e s c r i b e d I n t h e a a p p r o p r i a t e c h a p t e r s . S i n c e m o s t o f t h e r e a g e n t s a n d t h e p r o d u c t s w e r e h y g r o s c o p i c , . . s p e c i a l p r e c a u t i o n s w e r e t a k e n a t a l l s t a g e s t o a v o i d c o n t a c t w i t h m o i s t a i r . A P y r e x v a c u u m l i n e a n d a m e t a l v a c u u m l i n e w e r e u s e d t o m a n i p u l a t e g a s e s a n d v o l a t i l e m a t e r i a l s . S o l i d s w e r e h a n d l e d i n a d r y b o x . I I . B . V A C U U M L I N E S I l i i B . l . P Y R E X V A C U U M L I N E A g e n e r a l p u r p o s e P y r e x v a c u u m l i n e o f a b o u t 6 0 c m l e n g t h w i t h f i v e o u t l e t s f i t t e d w i t h K o n t e s T e f l o n s t e m s t o p -c o c k s w a s u s e d t o m a n i p u l a t e v o l a t i l e l i q u i d s a n d g a s e s , f o r w h i c h t h e r e a c t i o n w i t h t h e g l a s s I s n e g l i g i b l e . T h i s v a c u u m l i n e w a s c o n n e c t e d t o a W e l c h D u o - S e a l m e c h a n i c a l p u m p ( m o d e l 1 4 0 5 ) v i a a l i q u i d N 2 c o l d - t r a p t o p r o t e c t t h e p u m p f r o m c o r r o s i v e v o l a t i l e m a t e r i a l s . P r e s s u r e s f r o m c a . 0 . 5 T o r r t o 1 a t m . w e r e m e a s u r e d u s i n g a m e r c u r y m a n o m e t e r . W h e n h a n d l i n g r e a g e n t s w h i c h w e r e k n o w n t o r e a c t r a p i d l y w i t h m e r c u r y , t h e o u t l e t f o r t h e m e r c u r y m a n o m e t e r w a s c l o s e d a n d t h e r e q u i r e d 6 9 p r e s s u r e s w e r e m a i n t a i n e d b y k e e p i n g t h e s o u r c e o f v a p o u r i n c o n s t a n t t e m p e r a t u r e s l u s h b a t h s m a d e b y a d d i n g s u f f i c i e n t a m o u n t s o f d r y i c e i n t o t r i c h l o r o e t h y l e n e i n a D e w a r f l a s k . W h e n t r a n s f e r r i n g l i q u i d s , a T - c o n n e c t i n g b r i d g e w a s a t t a c h e d t o t h e v a c u u m l i n e . T h i s T - p i e c e h a d B I O s o c k e t s a t e i t h e r e n d , a n d a B I O c o n e c o n n e c t i n g i t t o t h e m a i n m a n i f o l d v i a a K o n t e s T e f l o n s t e m s t o p c o c k . A t y p i c a l v a c u u m g e n e r a t e d _ 2 o n s u c h a l i n e w a s o f t h e o r d e r o f 1 0 T o r r . I I . B . 2 . M E T A L V A C U U M L I N E A m e t a l v a c u u m l i n e w a s u s e d t o m a n i p u l a t e A s F j - , d u e t o i t s v e r y h i g h r e a c t i v i t y w i t h g l a s s a t r o o m t e m p e r a t u r e . T h i s v a c u u m l i n e w a s m a d e o f 1 / 4 i n c h O . D . m o n e l t u b i n g e q u i p p e d w i t h W h i t e y s t a i n l e s s s t e e l v a l v e s ( I K S 4 3 1 6 ) , a n d w a s a t t a c h e d t o t h e m e c h a n i c a l p u m p v i a a g l a s s t r a p c o o l e d b y l i q u i d N ^ . C o p p e r t u b i n g ( 1 / 4 i n c h O . D . ) w a s u s e d a t t h e m e t a l g l a s s j o i n t . T h e p r e s s u r e i n t h e s y s t e m w a s m o n i t o r e d b y a N R S 8 0 1 t h e r m o c o u p l e v a c u u m g a u g e . T y p i c a l v a c u u m - 4 g e n e r a t e d i n t h i s m a n i f o l d w a s o f t h e o r d e r o f 1 0 T o r r . T h e b a s i c h a n d l i n g a n d m a n i p u l a t i o n t e c h n i q u e s o n t h e v a c u u m l i n e 8 3 w e r e s i m i l a r t o t h o s e d e s c r i b e d b y P e a c o c k A d i f f e r e n t m e t a l l i n e o f a m o r e s p e c i f i c d e s i g n w a s u s e d f o r t h e s y n t h e s i s o f S o 0 r F o a n d i t i s d e s c r i b e d i n J I fa I s e c t i o n I I . G . 70 I I . C . R E A C T I O N V E S S E L S I I . C . l . P Y R E X V E S S E L S P y r e x r e a c t i o n v e s s e l s w e r e u s e d f o r m o s t r e a c t i o n s . T h e s e P y r e x v e s s e l s w e r e m a i n l y o f t w o t y p e s . T h e s i m p l e s t t y p e w a s a t w o - p a r t r e a c t o r w h i c h c o n s i s t e d o f a 5 0 m l E r l e n m e y e r f l a s k w i t h a s t a n d a r d t a p e r B 1 9 g r o u n d g l a s s c o n e a n d a n a d a p t e r t o p c o n s i s t i n g o f a K o n t e s T e f l o n s t e m s t o p -c o c k b e t w e e n a B 1 9 s o c k e t a n d a B I O c o n e f o r a t t a c h m e n t t o t h e v a c u u m l i n e a s s h o w n i n F i g . 2 . 1 ( a ) . T h e f l a t b o t t o m o f a n E r l e n m e y e r f l a s k p e r m i t t e d t h e s p r e a d i n g o u t o f t h e p o w d e r e d g r a p h i t e , o r t h e i n t e r c a l a t i o n c o m p o u n d s h e n c e i n c r e a s i n g t h e a r e a o f s a m p l e e x p o s e d t o i n t e r c a l a n t v a p o u r , w h e n t h e i n t e r c a l a t i o n w a s c a r r i e d o u t a t r o o m t e m p e r a t u r e u s i n g t h e v a p o u r t r a n s p o r t m e t h o d . A l s o u n i f o r m e v a c u a t i o n o f t h e s a m p l e , w h e n r e m o v i n g t h e e x c e s s r e a g e n t s a n d b y p r o d u c t s w a s f a c i l i t a t e d b y t h e e v e n s p r e a d o f t h e s o l i d o n t h e f l a t b o t t o m o f t h e r e a c t o r . T h e t w o - p a r t a r r a n g e m e n t w a s u s e f u l f o r a d d i t i o n o r r e m o v a l o f s a m p l e s i n t h e s h a p e o f b i g p l a t e s , w i t h o u t h a v i n g t o b r e a k t h e r e a c t o r . T h e p r e s e n c e o f g r e a s e ( F l u o r o l u b e g r e a s e w a s u s e d e x t e n s i v e l y ) i n t h e g r o u n d g l a s s j o i n t n e v e r t h e l e s s c a u s e d s o m e c o n t a m i n a t i o n p r o b l e m s i n s o m e o f t h e r e a c t i o n s o f S o 0 r F . B r o m i n e ( I ) f l u o r o s u l f a t e , B r S 0 o F , Z b Z o r e a c t e d w i t h g r e a s e w i t h e v o l u t i o n o f g a s e o u s B r ^ w h i c h d i s s o l v e d i n t h e B r S O g F r e c o g n i z a b l e b y i t s d a r k r e d c o l o u r . T o a v o i d i n t e r f e r e n c e f r o m g r e a s e , o n e - p a r t r e a c t o r s w e r e u s e d f o r m o s t o f t h e r e a c t i o n s . T y p i c a l o n e - p a r t r e a c t o r s 7 . 1 F I G . 2 . 1 P Y R E X R E A C T I O N V E S S E L S ( A ) T W O - P A R T R E A C T I O N V E S S E L ( B ) S E A L - O F F O N E - P A R T R E A C T I O N V E S S E L 7 2 t h a t w e r e u s e d a r e s h o w n i n F i g u r e s 2 . 1 ( b ) , 2 . 2 ( a ) a n d 2 . 2 ( b ) . T h e o n e - p a r t r e a c t o r o f t h e t y p e s h o w n i n F i g . 2 . 1 ( b ) c o n s i s t s o f a P y r e x E r l e n m e y e r f l a s k ( 5 0 m l ) w i t h a c o n s t r i c t i o n a n d B 1 9 c o n e a t t h e t o p a n d a s i d e a r m l e a d i n g t o a B I O c o n e v i a a K o n t e s T e f l o n s t e m s t o p c o c k . A f t e r a d d i n g t h e s o l i d r e a c t a n t s i n t h e d r y b o x , t h e c a p p e d r e a c t i o n v e s s e l w o u l d b e f l a m e s e a l e d a t t h e c o n s t r i c t i o n . T h e l i q u i d o r g a s e o u s r e a g e n t s w o u l d t h e n b e a d d e d t h r o u g h t h e v a c u u m l i n e . T h e o n l y d i s a d v a n t a g e o f t h i s t y p e o f r e a c t o r w a s t h a t i t h a d t o b e b r o k e n i n t h e d r y b o x t o r e m o v e s o l i d p r o d u c t s . O n e - p a r t r e a c t i o n v i a l s ( F i g . 2 . 2 ( a ) ) a n d o n e - p a r t r e a c t i o n b u l b s ( F i g . 2 . 2 ( b ) ) w e r e a l s o u s e d f o r r e a c t i o n s , w h e r e p o w d e r y s a m p l e s w e r e e a s i l y a d d e d o r r e m o v e d i n t h e d r y b o x . T h e s e r e a c t o r s w e r e f o u n d s u i t a b l e f o r r e a c t i o n s i n v o l v i n g g r a p h i t e a n d a l i q u i d r e a g e n t , w h e r e t h e l i q u i d c o u l d b e d i s t i l l e d i n t o t h e r e a c t o r a n d t h e m i x t u r e m a g n e t i c a l l y s t i r r e d . T e f l o n c o a t e d s t i r r i n g b a r s w e r e u s e d t o s t i r t h e s o l i d - l i q u i d m i x t u r e s u s i n g a n e x t e r n a l m a g n e t i c s t i r r e r . T h e c a p a c i t y o f t h e r e a c t i o n v e s s e l s w a s a b o u t 1 0 0 m l , a n d l a r g e r v e s s e l s o f t h e t y p e s h o w n i n F i g . 2 . 2 ( a ) o f c a p a c i t y ^ 5 0 0 m l w e r e u s e d f o r t h e s t o r a g e o f l i q u i d r e a g e n t s s u c h a s ^2^Q^2' I I . C . 2 . M E T A L R E A C T O R A t w o - p a r t m o n e l m e t a l r e a c t i o n v e s s e l ( F i g . 2 . 3 ) -w a s u s e d f o r r e a c t i o n s i n v o l v i n g A s F , - . T h e t o p p a r t o f t h i s r e a c t o r w a s f i t t e d w i t h a W h i t e y v a l v e a n d a s w a g e l o c k ( 1 / 4 " ) c o n n e c t o r t o a t t a c h d i r e c t l y t o t h e m e t a l v a c u u m l i n e . T h e 73 F I G . 2.2 PYREX O N E - P A R T R E A C T I O N AND STORAGE V E S S E L S 74 V I — J Whitey Valve (1KS4) 13 Monel Metal Reaction Vessel F I G . 2 . 3 M O N E L M E T A L T W O - P A R T R E A C T I O N V E S S E L 7 5 t o p a n d b o t t o m p a r t s w a r e h e l d t o g e t h e r w i t h s i x b o l t s t o w i t h s t a n d h i g h p r e s s u r e . A T e f l o n 0 - r i n g w a s u s e d a s g u a r d . T h e t o t a l v o l u m e o f t h i s r e a c t o r w a s ^ 1 5 0 m l . S o l i d s a m p l e s w e r e e a s i l y l o a d e d a n d r e m o v e d i n t h e d r y b o x , h o w e v e r t h e w e i g h t c h a n g e s d u r i n g r e a c t i o n s c o u l d n o t b e d e t e r m i n e d a c c u r a t e l y d u e t o t h e w e i g h t o f t h i s r e a c t o r . I I . D . S P E C I A L G L A S S A P P A R A T U S I I . D . l . S o 0 r F o A D D I T I O N T R A P S z b Z  I n s o m e p r e p a r a t i o n s a n e x a c t a m o u n t o f S „ 0 „ F „ h a d z b z t o b e a d d e d t o a r e a c t i o n m i x t u r e . T o a c c o m p l i s h t h i s a m e a s u r i n g t r a p ( F i g . 2 . 4 ) w a s c o n s t r u c t e d t o d e l i v e r v o l u m e s u p t o 0 . 5 0 m l . T h i s t r a p c o n s i s t e d o f a p i p e t t e ( 0 . 0 0 - 0 . 5 0 m l ) s e a l e d o f f a t o n e e n d a n d c o n n e c t e d t o a B I D c o n e t h r o u g h a p i e c e o f P y r e x t u b i n g ( 2 0 m m l o n g a n d 1 0 m m O . D . ) , a n d a T e f l o n s t e m s t o p c o c k . T h i s t r a p w a s c a l i b r a t e d p r i o r t o u s e t o a l l o w t h e t r a n s f e r o f e x a c t v o l u m e s o f s o l u t i o n s , I t s s m a l l s i z e a l l o w e d a l s o t h e w e i g h i n g o f t h i s t r a p w i t h t h e l i q u i d , t h u s p r o v i d i n g a d i r e c t c o n t r o l . T h e t r a n s f e r o f ^ f l b ^ l a r e a c t o r c o u l d b e m a d e q u a n t i t a t i v e l y b y a t t a c h i n g t h e t r a p t o o n e a r m o f a T - c o n n e c t i n g b r i d g e t h e o t h e r a r m o f w h i c h i s a t t a c h e d t o t h e r e a c t o r , a n d c a r r y i n g o u t a s l o w s t a t i c v a c u u m d i s t i l l a t i o n . W h e n l a r g e r a m o u n t s o f S 2 0 g F 2 w e r e r e q u i r e d f o r r r e a c t i o n s , a 1 0 0 m l o n e - p a r t r e a c t i o n v i a l w a s c a l i b r a t e d i n a s i m i l a r m a n n e r a s d e s c r i b e d p r e v i o u s l y a n d w a s f o u n d t o 7 6 m l fo - i 0-2 (K3 M l F I G . 2 . 4 S o 0 r F o A D D I T I O N T R A P 2 b z 7 7 d e l i v e r 0 . 4 0 g o f S ^ O g F ^ ^ p e r m m . l e n g t h o f t h e c y l i n d r i c a l p a r t . I I . D . 2 . V A C U U M F I L T R A T I O N O c c a s i o n a l l y w h e n t h e s a m p l e s w e r e w a s h e d w i t h 8 4 a n o t h e r r e a g e n t , a v a c u u m f i l t r a t i o n a p p a r a t u s s h o w n m F i g . 2 . 5 , w a s u s e d f o r t h i s p u r p o s e . T h e s o l i d s a m p l e s w e r e a d d e d i n t o t h e t o p p a r t o f t h e f i l t e r i n t h e d r y b o x . T h e l i q u i d w a s e i t h e r d i s t i l l e d i n t o i t o r t r a n s f e r r e d i n t h e d r y b o x u s i n g a p i - p u m p p i p e t t i n g d e v i c e a t t a c h e d t o a p i p e t t e . A f t e r w a s h i n g t h e p r o d u c t t h e l i q u i d w a s " f i l t e f e d v o f f b y a t t a c h i n g t h e v a c u u m f i l t e r t o t h e v a c u u m m a n i f o l d t h r o u g h t h e B I O c o n e . I I . E . G E N E R A L E Q U I P M E N T I I . E . l . D R Y B O X T h e h a n d l i n g o f h y g r o s c o p i c s o l i d s , a n d l i q u i d s w i t h v e r y l o w v o l a t i l i t y a t r o o m t e m p e r a t u r e r e q u i r e d - a m o i s t u r e f r e e e n v i r o n m e n t . T h i s w a s p r o v i d e d b y a V a c u u m A t m o s p h e r e C o r p o r a t i o n D r y - L a b , m o d e l H E - 4 3 - 2 , e q u i p p e d w i t h a D r i - T r a i n , m o d e l H E - 9 3 - B r e c i r c u l a t i n g u n i t . D r y n i t r o g e n , c o n s t a n t l y c i r c u l a t e d o v e r m o l e c u l a r s i e v e s w a s u s e d t o p r o v i d e a n i n e r t a t m o s p h e r e . T h e s e s i e v e s w e r e r e g e n e r a t e d a f t e r a b o u t a m o n t h ' s u s e b y t h e h e a t i n g u n i t . A d i s h o f P ^ 0 k e p t i n s i d e t h e d r y b o x s e r v e d a s a m o i s t u r e i n d i c a t o r . 7 9 I I . E . 2 . . I . R . S P E C T R O S C O P Y I n f r a r e d s p e c t r a w e r e r e c o r d e d a t r o o m t e m p e r a t u r e u s i n g a P e r k i n - E l m e r 5 9 8 g r a t i n g s p e c t r o p h o t o m e t e r , w i t h a s p e c t r a l r a n g e o f 4 0 0 0 - 2 0 0 c m " 1 . A g C l , A g B r a n d K R S - 5 ( t h a l l i u m b r o m i d e - i o d i d e ) w i n d o w s w i t h t r a n s m i s s i o n r a n g e - 1 - 1 - 1 d o w n t o 4 0 0 c m , 3 0 0 c m a n d 2 5 0 c m r e s p e c t i v e l y w e r e u s e d . S i n c e t h e s a m p l e s w e r e h y g r o s c o p i c a n d o f t e n r e a c t e d w i t h c o n v e n t i o n a l m u l l i n g a g e n t s l i k e N u j o l a n d h e x a c h l o r o b e n z e n e , a s o l i d f i l m o f t h e s a m p l e b e t w e e n t h e w i n d o w s w a s p r o t e c t e d f r o m a t m o s p h e r i c m o i s t u r e b y b l a c k e l e c t r i c a l i n s u l a t i o n t a p e w r a p p e d a r o u n d t h e e d g e s o f t h e w i n d o w s . S a m p l e s w e r e p r e p a r e d i n s i d e t h e d r y b o x a n d s p e c t r a w e r e r e c o r d e d a s s o o n a s t h e s a m p l e s w e r e t a k e n o u t o f t h e d r y b o x , t o p r e v e n t a t t a c k o n t h e w i n d o w s b y t h e s a m p l e s . S p e c t r a w e r e r e c o r d e d i n b o t h t r a n s m i s s i o n a n d r e f l e c t i o n g e o m e t r i e s . F o r t h e l a t t e r a P e r k i n - E l m e r s p e c u l a r r e f l e c t a n c e a c c e s s o r y , ( m o d e l 1 8 6 - 0 1 8 8 ) w a s f i t t e d t o t h e I . R . s p e c t r o p h o t o m e t e r . T h e r e f l e c t i o n g e o m e t r y i n t h e s p e c u l a r r e f l e c t a n c e a r r a n g e m e n t w a s f o u n d t o b e v e r y u s e f u l f o r o p a q u e s a m p l e s l i k e G I C s . A s s h o w n I n F i g . 2 . 6 , t h e t o r o i d a l m i r r o r ( M g ) , w h i c h r e f o c u s e s t h e s o u r c e i m a g e o n t h e m o n o c h r o m a t o r e n t r a n c e s l i t , e n h a n c e s t h e a b i l i t y o f t h i s a c c e s s o r y t o m e a s u r e r e f l e c t a n c e f r o m a s m a l l s a m p l e a r e a , t h e r e b y p r e v e n t -i n g t h e a b s o r p t i o n o f r a d i a t i o n . I n a d d i t i o n , a m o n e l m e t a l g a s c e l l , 7 c m l o n g a n d e q u i p p e d w i t h A g C l w i n d o w s , w a s u s e d f o r o b t a i n i n g t h e I . R . s p e c t r a o f g a s e s . A l l i n f r a r e d s p e c t r a w e r e c a l i b r a t e d w i t h a p o l y s t y r e n e f i l m 80 F I G . 2 . 6 O P T I C A L S C H E M A T I C A R R A N G E M E N T F O R S P E C U L A R R E F L E C T A N C E 8 1 r e f e r e n c e . I I . E . 3 . R A M A N S P E C T R O S C O P Y R a m a n s p e c t r a w e r e r e c o r d e d u s i n g a S p e x R a m a l o g - 5 s p e c t r o m e t e r , e q u i p p e d w i t h a S p e c t r a P h y s i c s 1 6 4 A r g o n i o n l a s e r . T h e g r e e n l i n e a t 5 1 4 . 5 n m w a s u s e d f o r e x c i t a t i o n . L i q u i d s a m p l e s w e r e v a c u u m d i s t i l l e d i n t o q u a r t z c a p i l l a r i e s w h i c h w e r e t h e n f l a m e s e a l e d . F o r s o l i d s a m p l e s , b e c a u s e o f 8 5 t h e i r v e r y h i g h a b s o r p t i o n , a b a c k s c a t t e r i n g g e o m e t r y w a s a d o p t e d . T o o b t a i n t h e h i g h e s t i n t e n s i t y o f t h e p e a k s , t h e i n c i d e n t l a s e r w a s a t a n a n g l e o f i n c i d e n c e e q u a l o r c l o s e r t o t h e B r e w s t e r a n g l e o f t h e t w o m e d i a . F o r t w o m e d i a w i t h t h e r e f r a c t i v e i n d i c e s n ^ a n d a s s h o w n i n F i g . 2 . 7 , - 1 n 2 t h e B r e w s t e r a n g l e 9 = t a n ( — } ) . F o r e . g . w h e n t h e n l l a s e r e n t e r s f r o m a i r ( r e f r a c t i v e i n d e x = 1 ) I n t o a q u a r t z w i n d o w ( r e f r a c t i v e i n d e x = 1 . 4 5 8 4 ) , t h e B r e w s t e r a n g l e f o r t h e s e t w o m e d i a w o u l d b e 5 5 ° 8 4 ' . A t t h i s a n g l e o f i n c i d e n c e , l o s s o f l a s e r p o w e r a t t h e q u a r t z w i n d o w w o u l d b e m i n i m i z e d . A l s o t h i s a r r a n g e m e n t p r e v e n t s a n y c h a n g e i n p o l a r i z a t i o n o f t h e i n c i d e n t b e a m a n d h e n c e f o r s a m p l e s m a d e f r o m H O P G p l a t e s , t h e s p e c t r a c a n b e t a k e n w i t h t h e i n c i d e n t e l e c t r i c f i e l d i n t h e l a y e r p l a n e s s o t h a t o n l y t h e i n - p l a n e l a t t i c e m o d e s w o u l d b e e x c i t e d . A t h i n f i l m o f t h e s a m p l e w a s t r a n s f e r r e d i n t o t h e T e f l o n c e l l , i n t h e d r y b o x . A f t e r p l a c i n g t h e q u a r t z w i n d o w o v e r t h i s f i l m i t w a s c o v e r e d w i t h a T e f l o n O - r i n g a n d b l a c k e l e c t r i c a l i n s u l a t i o n t a p e w a s w r a p p e d a r o u n d t h e e d g e t o 8 2 F I G . 2 . 7 T H E B R E W S T E R A N G L E 8 3 p r e v e n t a n y c o n t a m i n a t i o n b y a t m o s p h e r i c m o i s t u r e . T h e c e l l w a s t h e n m o u n t e d i n t h e b a c k s c a t t e r i n g a r r a n g e m e n t a s s h o w n i n F i g . 2 . 8 . T h e a n g l e - o f i n c i d e n c e o f t h e ^ l a s e r b e a m w a s a d j u s t e d t o a s e m i - B r e w s t e r a n g l e s o t h a t m a x i m u m i n t e n s i t y o f t h e p e a k s c a n b e o b t a i n e d . T h e m i r r o r a n d t h e s a m p l e h o l d e r w e r e a d j u s t e d s o t h a t t h e l a s e r b e a m c a n b e c o l l e c t e d a t 9 0 ° t o t h e s a m p l e s u r f a c e , w h i l e m a i n t a i n i n g a s e m i - B r e w s t e r a n g l e o f i n c i d e n c e . S a m p l e s w e r e e x c i t e d w i t h l o w l a s e r p o w e r s ( < 5 0 m W ) t o a v o i d d e i n t e r c a l a t i o n d u e t o l o c a l h e a t i n g o f t h e s a m p l e . 8 6 A r o t a t i n g R a m a n c e l l w a s u s e d t o o b t a i n s p e c t r a o f s o m e o f t h e s a m p l e s w h i c h w e r e f o u n d t o l i b e r a t e p a r t o f t h e i n t e r c a l a t e d m a t e r i a l e v e n a t v e r y l o w l a s e r p o w e r . T h i s c e l l w a s o f c y l i n d r i c a l s h a p e ( d i a m e t e r = 2 . 0 c m a n d h e i g h t = 3 . 0 c m ) , a n d h a d a B 1 9 s o c k e t a t t h e t o p . S a m p l e s w e r e t r a n s f e r r e d i n t o t h i s c e l l I n t h e d r y b o x , a n d t h e t o p w a s c l o s e d b y a t i g h t l y f i t t i n g T e f l o n s t o p c o c k w h i c h w a s h e l d a t t a c h e d t o t h e c e l l b y t w o m e t a l s p r i n g s . T h e s t o p c o c k h a d a m e t a l r o d a t t a c h e d a t t h e t o p t h r o u g h w h i c h i t w a s c o n n e c t e d t o a m o t o r . T h e r e s t o f t h e o p t i c a l a r r a n g e m e n t s w e r e s i m i l a r t o t h o s e d e s c r i b e d b e f o r e . T h e c y l i n d r i c a l c e l l w a s r o t a t e d b y t h e m o t o r a t ( 2 0 0 - 5 0 0 ) r . p . m . P o w d e r e d s a m p l e s a c c u m u l a -t e d o n . t h e c i r c u l a r e d g e o f t h e c e l l d u e t o r o t a t i o n , a n d t h e s c a t t e r e d l i g h t f r o m t h e s a m p l e w a s c o l l e c t e d a t 9 0 ° t o t h e e d g e o f t h e c e l l . T h i s a r r a n g e m e n t m i n i m i z e d t h e d e c o m p o s i t i o n o f t h e u n s t a b l e s a m p l e s . L a t t i c e v i b r a t i o n a l m o d e s o b s e r v e d b y t h i s m e t h o d w e r e o f l o w e r i n t e n s i t y a n d b r o a d e r t h a n t h o s e o b s e r v e d i n s t a t i o n a r y s a m p l e s . H e n c e u s e 8 4 Back-scattering Arrangement Used for Raman Spectra mirror F I G . 2 . 8 8 5 o f t h i s m e t h o d w a s r e s t r i c t e d t o s a m p l e s w h i c h w e r e f o u n d t o d e c o m p o s e w h e n t a k i n g t h e i r R a m a n s p e c t r a i n t h e s t a t i o n a r y c e l l . I I . E . 4 . E L E C T R O N S P I N R E S O N A N C E A V a r i a n A s s o c i a t e s m o d e l E - 3 s p e c t r o m e t e r e q u i p p e d w i t h a 1 0 0 . K H z f i e l d m o d u l a t i o n w a s u s e d t o r e c o r d e l e c t r o n s p i n r e s o n a n c e s p e c t r a a t r o o m t e m p e r a t u r e . A H e w l e t t - P a c k a r d 5 2 4 5 L e l e c t r o n i c c o u n t e r w i t h a 5 2 5 . 6 n m f r e q u e n c y c o n v e r t e r 8 - 1 8 G H z w a s u s e d t o c a l i b r a t e t h e X - b a n d m i c r o w a v e f r e q u e n c y . P o w d e r e d s a m p l e s w e r e c o n t a i n e d i n m e l t i n g p o i n t c a p i l l a r i e s t h a t w e r e t e s t e d b e f o r e h a n d t o c o n f i r m t h e a b s e n c e o f a n y s p u r i o u s s i g n a l . I I . E . 5 . N U C L E A R M A G N E T I C R E S O N A N C E S o l i d s t a t e N M R s p e c t r a w e r e r e c o r d e d a t r o o m t e m p e r a t u r e u s i n g a B r u k e r C X P - 2 0 0 F T - N M R s p e c t r o m e t e r 1 9 1 e q u i p p e d w i t h a h i g h p o w e r p r o b e . F a n d H N M R s p e c t r a w e r e t a k e n a t 1 8 8 . 1 5 M H z a n d 2 0 0 . 0 0 M H z r e s p e c t i v e l y . S a m p l e s 1 9 1 f o r b o t h F a n d H N M R s p e c t r a w e r e s e a l e d m N M R t u b e s o f 1 3 3 0 m m l e n g t h a n d 5 m m O . D . S o l i d s t a t e C N M R s p e c t r a w e r e t a k e n a t r o o m t e m p e r a t u r e a t 5 0 . 3 0 M H z . S a m p l e s f o r t h e s e s p e c t r a w e r e s e a l e d i n c y l i n d r i c a l t u b e s o f 5 0 m m l e n g t h a n d 1 0 m m d i a m e t e r . H i g h r e s o l u t i o n N M R s p e c t r a o f l i q u i d s a n d s o l u t i o n s w e r e r e c o r d e d i n : 1 H - V a r i a n E M - 3 6 0 , o p e r a t e d a t 6 0 M H z . 8 6 F - C . W . s p e c t r a w e r e r e c o r d e d o n a V a r i a n E M - 3 6 0 , o p e r a t e d a t 5 6 . 4 5 M H z . T h e l o c k s i g n a l w a s p r o v i d e d e i t h e r b y e x t e r n a l C F C 1 3 o r i n t e r n a l H S O ^ F . F T - N M R s p e c t r a w e r e r e c o r d e d o n a V a r i a n X L - 1 0 0 o p e r a t e d a t 9 4 . 1 M H z . T h e l o c k s i g n a l w a s p r o v i d e d b y e x t e r n a l D r - a c e t o n e . b T h e l i q u i d s a m p l e s w e r e c o n t a i n e d i n s t a n d a r d N M R t u b e s ( 5 m m O . D . ) . A l l c h e m i c a l s h i f t s a r e r e p o r t e d i n 6 s c a l e w i t h p o s i t i v e s h i f t s t o t h e h i g h f r e q u e n c y ( l o w f i e l d ) o f t h e r e f e r e n c e . T h e f o l l o w i n g l i q u i d s w e r e u s e d a s e x t e r n a l r e f e r e n c e s : T e t r a m e t h y l s i l a n e ( T M S ) F r e o n 1 1 ( C F C l g ) B e n z e n e I I . E . 6 . X - R A Y D I F F R A C T I O N X - r a y p o w d e r p h o t o g r a p h s w e r e o b t a i n e d o n a P h i l l i p s p o w d e r c a m e r a o f 5 7 m m r a d i u s a n d h a v i n g a c o n v e n t i o n a l o S t r a u m a n i s a r r a n g e m e n t . C u - K X - r a y r a d i a t i o n ( X = 1 . 5 4 0 5 A ) w a s u s e d w i t h a n i c k e l f i l t e r t o r e d u c e K . r a d i a t i o n . T h e p p o w d e r e d s a m p l e s w e r e s e a l e d I n 0 . 5 m m O . D . , L i n d e m a n n g l a s s c a p i l l a r i e s . K o d a k N S - 3 9 2 T f i l m w a s u s e d t o o b t a i n X - r a y p o w d e r p h o t o g r a p h s . T i m e o f e x p o s u r e g e n e r a l l y r a n g e d b e t w e e n 5 - 1 2 h o u r s . H N M R -1 9 F N M R -1 3 C N M R -8 7 T h e l i n e s i n t h e \ p h o t o g r a p h o b t a i n e d w e r e m e a s u r e d o n a f i l m i l l u m i n a t o r . T h i s i l l u m i n a t o r h a d a m e t e r s t i c k t o w h i c h a s l i d i n g a s s e m b l y c o n t a i n i n g a V e r n i e r s c a l e a n d a m a g n i f i e d c r o s s - h a i r f o r l o c a t i n g t h e d i f f r a c t i o n l i n e s w a s a t t a c h e d . T h e r e l a t i v e i n t e n s i t y o f t h e l i n e s w e r e m e a s u r e d b y u s i n g a d e n s i t o m e t e r . I I . E . 7 . E L E C T R I C A L C O N D U C T A N C E ' M E A S U R E M E N T S I I . E . 7 ( a ) E L E C T R I C A L C O N D U C T A N C E O F S U S P E N S I O N S O F G R A P H I T E F L U O R O S U L F A T E I N F L U O R O S U L F U R I C A C I D E l e c t r i c a l c o n d u c t a n c e s o f s u s p e n s i o n s o f g r a p h i t e f l u o r o s u l f a t e C ^ S O ^ F i n H S O ^ F w e r e m e a s u r e d u s i n g a W a y n e - K e r r 8 7 U n i v e r s a l B r i d g e , m o d e l B 2 2 1 A . T h e c o n d u c t i v i t y c e l l s h o w n i n F i g . 2 . 9 , h a d p l a t i n u m e l e c t r o d e s w h i c h w e r e c o a t e d w i t h p l a t i n u m b l a c k . T h i s c o a t i n g w a s r e n e w e d b y e l e c t r o p l a t i n g f r o m a s o l u t i o n o f H 0 P t C l c • . T h e c e l l c o n s t a n t w a s d e t e r m i n e d 2 b 8 8 u s i n g a q u e o u s K C 1 s o l u t i o n s o f ^ 0 . 1 M a n d h a d v a l u e s r a n g i n g _ 1 f r o m 8 . 0 5 t o 8 . 1 0 c m . A n o i l b a t h o f ^ 3 5 L c a p a c i t y a n d a S a r g e n t T h e r m o n i t o r , m o d e l S T t h e r m o s t a t w e r e u s e d t o m a i n t a i n a t e m p e r a t u r e o f ( 2 5 . 0 0 ± 0 . 0 1 ) ° C f o r c o n d u c t i v i t y m e a s u r e m e n t s . A f t e r d r y i n g a n d w e i g h i n g t h e c o n d u c t a n c e c e l l , i t w a s a t t a c h e d t o t h e f l u o r o s u l f u r i c a c i d d o u b l e d i s t i l l a t i o n a p p a r a t u s . A p p r o x i m a t e l y 1 0 m l o f H S O g F w e r e c o l l e c t e d i n t h e c e l l , a n d i t s w e i g h t w a s c h e c k e d o n a b a l a n c e . T h i s c e l l w a s t h e n i m m e r s e d p a r t i a l l y i n t h e o i l b a t h s o t h a t t h e a c i d l e v e l i n s i d e t h e c e l l w a s w e l l ^ b e l o w t h e o i l l e v e l , a n d a n F I G . 2 . 9 C O N D U C T I V I T Y C E L L 89 I o FIG. 2 . 1 0 Weight D r o p p e r u s ed f o r So l u t e A d d i t i o n s 9 0 e q u i l i b r i u m p e r i o d o f a b o u t 1 0 m i n u t e s w e r e a l l o w e d b e f o r e m e a s u r i n g t h e c o n d u c t a n c e . I t w a s o b s e r v e d t h a t t h e c o n d u c - v , t a n c e r e m a i n e d c o n s t a n t a f t e r a b o u t 5 m i n u t e s . S i n c e t h e s o l i d m a t e r i a l a d d e d t o H S O ^ F d u r i n g c o n d u c t a n c e m e a s u r e m e n t s w a s h y g r o s c o p i c , t h i s a d d i t i o n h a d t o b e d o n e b y u s i n g a w e i g h t d r o p p e r , s h o w n i n F i g . 2 . 1 0 . T h i s d r o p p e r w a s f i l l e d i n t h e d r y b o x a n d w e i g h e d o u t s i d e b e f o r e a n d a f t e r e a c h a d d i t i o n o f t h e c o m p o u n d t o H S O ^ F . T h e c o n d u c t a n c e c e l l w a s s h a k e n a f t e r e a c h a d d i t i o n o f t h e s o l i d m a t e r i a l t o e n s u r e c o m p l e t e m i x i n g o f t h e s o l i d a n d t h e a c i d . T h e a d d i t i o n o f s o l i d m a t e r i a l , n e v e r t h e l e s s i n t r o d u c e d a s m a l l a m o u n t o f m o i s t u r e i n t o t h e c e l l , h e n c e c a u s i n g a s m a l l i n c r e a s e i n c o n d u c t a n c e d u e t o f o r m a t i o n o f H F a n d H ^ S O ^ . T h i s e f f e c t w a s t a k e n i n t o c o n s i d e r a t i o n w h e n i n t e r p r e t i n g t h e r e s u l t s . I I . E . 7 C b ) E L E C T R I C A L C O N D U C T I V I T Y O F A C C E P T O R G I C s R o o m t e m p e r a t u r e e l e c t r i c a l c o n d u c t i v i t y m e a s u r e r - : , m e n t s o n g r a p h i t e i n t e r c a l a t i o n c o m p o u n d s w e r e m a d e b y t h e c o n t a c t l e s s r a d i o f r e q u e n c y i n d u c t i o n t e c h n i q u e . D e t a i l s o f t h i s m e t h o d a r e d i s c u s s e d i n C h a p t e r V I I . I I . F . C H E M I C A L S A N D O T H E R M A T E R I A L S " : I I . F . l . C H E M I C A L S O B T A I N E D F R O M C O M M E R C I A L S O U R C E S T h e f o l l o w i n g t a b l e l i s t s t h e c h e m i c a l s o b t a i n e d f r o m c o m m e r c i a l s o u r c e s a l o n g w i t h t h e i r s u p p l i e r s . 9 1 T A B L E , .2.1: C H E M I C A L S O B T A I N E D F R O M C O M M E R C I A L S O U R C E S S O U R C E C H E M I C A L S R E M A R K S A l l i e d C h e m i c a l s S03 ( S u l f a n ) H2S04 HS03F ( t e c h . ) 9 6 % A C S R e a g e n t . D o u b l e d i s t i l l e d a c c o r d i n g t o s e c t i o n ( i ) . M i n n e s o t a M i n i n g a n d M a n u f a c t u r i n g C o . HSO3CF3 D i s t i l l e d a s d e s c r i b e d i n s e c t i o n ( i i ) 3. M a l l i n c k r o d t I n c . B r , A n a l y t i c a l R e a g e n t , P u r i f i e d b y s t o r -i n g o v e r P2O5 " t o r e m o v e m o i s t u r e a n d K B r t o r e m o v e . C l 2 -4. M a t h e s o n o f C a n a d a L t d . C I , P a s s e d t h r o u g h K M n O u t o r e m o v e HC1 a n d b u b b l e d t h r o u g h c o n e . H2SO4 t o r e m o v e m o i s t u r e . S O , U s e d a s r e c e i v e d 9 8 % p u r e , p a s s e d t h r o u g h N a F d r y i n g t o w e r t o r e m o v e H F , 5. O z a r k M a h o n i n g C o S b F r P u r i f i e d a c c o r d i n g t o s e c t i o n ( i i i ) A s F c P u r i f i e d b y t r a p t o t r a p d i s t i l l a -t i o n . 9 2 A d d i t i o n a l p u r i f i c a t i o n s w e r e r e q u i r e d , f o r s o m e c h e m i c a l s , t h e m e t h o d s a d o p t e d t o p u r i f y t h e s e c h e m i c a l s a r e d e s c r i b e d b e l o w : ( i ) H S O g F C o m m e r c i a l l y a v a i l a b l e H S O ^ F w a s o f t e c h n i c a l g r a d e , t h e r e f o r e a d o u b l e d i s t i l l a t i o n m e t h o d w a s u s e d t o p u r i f y i t b e f o r e u s i n g f o r s y n t h e t i c r e a c t i o n s a n d c o n d u c t a n c e m e a s u r e -m e n t s . T h e P y r e x a p p a r a t u s u s e d f o r t h i s p u r p o s e i s s h o w n i n F i g . 2 . 1 1 . T h i s s y s t e m w a s f i r s t d r i e d b y f l a m i n g i t p e r i o d i c a l l y a n d f l u s h i n g o u t b y d r y N 2 • I n t h e f i r s t d i s t i l l a t i o n m o s t o f t h e H F i m p u r i t y w a s r e m o v e d f r o m t h e a c i d b y a c o u n t e r s t r e a m o f N 2 • T h e c o n s t a n t b o i l i n g f r a c t i o n a t 1 6 3 ° C f r o m t h e s e c o n d d i s t i l l a t i o n w a s c o l l e c t e d i n a s t o r a g e c o n t a i n e r . S p e c i f i c c o n d u c t a n c e o f t h e a c i d c o l l e c t e d - 4 - 1 - 1 w a s d e t e r m i n e d t o b e ( 1 . 1 0 - 1 . 3 0 ) x 1 0 o h m c m w h i c h w a s 8 9 - 4 - 1 - 1 s i m i l a r t o t h e r e p o r t e d v a l u e o f 1 . 0 8 5 x 1 0 o h m c m ( i i ) H S 0 3 C F 3 S i n c e t h e p u r i t y o f c o m m e r c i a l l y a v a i l a b l e H S 0 3 C F 3 w a s n o t k n o w n , i t w a s d i s t i l l e d a t r e d u c e d p r e s s u r e u s i n g a c o n v e n t i o n a l d i s t i l l a t i o n a p p a r a t u s e q u i p p e d w i t h a V i g r e u x c o l u m n , a n d a f r a c t i o n s e p a r a t o r . T h i s d i s t i l l a t i o n a p p a r a t u s w a s c o n n e c t e d t o t h e v a c u u m l i n e w i t h T y g o n t u b i n g . H S 0 3 C F 3 w a s d i s t i l l e d f r o m c o n c e n t r a t e d E ^ S O ^ , a d d e d t o r e m o v e H 2 0 , a t ^ 1 5 T o r r o f d r y N 2 . T h e c o n s t a n t b o i l i n g f r a c t i o n a t ^ 1 1 0 ° C w e r e c o l l e c t e d i n s t o r a g e c o n t a i n e r s . T h i s a c i d w a s d i s t i l l e d F I G . 2 . 1 1 F L U O R O S U L F U R I C A C I D D I S T I L L A T I O N A P P A R A T U S 94 b y t r a p t o t r a p d i s t i l l a t i o n b e f o r e u s e . ( i i i ) S b F c b A n t i m o n y p e n t a f l u o r i d e , S b F j - , w a s p u r i f i e d b y f i r s t p u r g i n g i t w i t h d r y i n a 5 0 0 m l t w o - n e c k e d f l a s k f i t t e d w i t h a D r i e r i t e g u a r d t u b e . M o s t o f t h e H F w a s r e m o v e d b y t h i s p r o c e s s a n d t h e ' ' m a t e r i a l b e c a m e r e l a t i v e l y v i s c o u s . T h i s w a s p u r i f i e d f u r t h e r b y d i s t i l l i n g u n d e r N 2 5 a n d s t o r e d i n a P y r e x c o n t a i n e r s h o w n i n F i g . 2 . 1 2 . T h e s m a l l a m o u n t o f H F t h a t r e m a i n e d a f t e r t h i s s t a g e w a s r e m o v e d b y i n t e r m i t t a n t p u m p i n g u n t i l t h e e v o l u t i o n o f g a s b u b b l e s w a s n o t o b s e r v e d . A n t i m o n y p e n t a f l u o r i d e w a s d i s t i l l e d f r o m t h i s s t o r a g e v e s s e l i n t o t h e r e a c t o r b y a t t a c h i n g t h e l a t t e r t o t h e s i d e a r m o f t h e s t o r a g e v e s s e l w h i c h w a s a t t a c h e d t o t h e v a c u u m m a n i f o l d . ( i v ) A s F 5 A r s e n i c p e n t a f l u o r i d e , A s F ^ , w a s p u r i f i e d b y t r a p t o t r a p d i s t i l l a t i o n a n d s t o r e d i n m o n e l m e t a l c o n t a i n e r s e q u i p p e d w i t h W h i t e y v a l v e s a n d S w a g e l o c k c o n n e c t i o n s . I I . F . 2 . O T H E R C O M M E R C I A L L Y O B T A I N E D M A T E R I A L  G R A P H I T E T h r e e t y p e s o f g r a p h i t e w e r e u s e d i n t h i s w o r k : ( a ) S P 1 . G R A P H I T E : S p e c t r o s c o p i c g r a d e p u r i f i e d n a t u r a l g r a p h i t e ( 5 0 y ) w a s o b t a i n e d f r o m U n i o n - C a r b i d e L t d . , 95 F I G . 2 . 1 2 S T O R A G E V E S S E L F O R SbF^ 9 6 T A B L E 2 . 2 : C O M M E R C I A L L Y A V A I L A B L E T Y P E S O F A P P A R A T U S A p p a r a t u s M a n u f a c t u r e r o r S u p p l i e r W e l s h D u o - S e a l V a c u u m P u m p , M o d e l 1 4 0 0 W e l s h S c i e n t i f i c C o m p a n y ; S k o k i e , I l l i n o i s . K o n t e s H i g h v a c u u m g l a s s a n d K o n t e s ; F r a n k l i n P a r k , I l l i n o i s T e f l o n - s t e m s t o p c o c k s M e t a l h i g h p r e s s u r e a n d v a c u u m v a l v e s W h i t e y ; C o l u m b i a V a l v e a n d F i t t i n g C o . , V a n c o u v e r , B r i t i s h C o l u m b i a . H o k e ; H o k e I n c . , C r e s k i l l , N e w J e r s e y . A u t o c l a v e ; A u t o c l a v e E n g i n e e r i n g I n c . , E r i e , P e n n s y l v a n i a . F l u o r o l u b e G r e a s e , G R - 9 0 H o o k e r C h e m i c a l C o r p o r a t i o n ; G R - 3 6 2 , F l u o r o l u b e O i l , M O - 1 0 N o r t h V a n c o u v e r , B r i t i s h C o l u m b i a . T y g o n t u b i n g T e f l o n c o a t e d s t i r r i n g b a r s F i s h e r r S c i e n t i f i c C o . ; V a n c o u v e r , B r i t i s h C o l u m b i a , L i n d e C h r o m a t o g r a p h - g r a d e 5 A m o l e c u l a r s i e v e s U n i o n C a r b i d e ; R e d o n d o B e a c h , C a l i f o r n i a . D r i - L a b ( V A C ) M o d e l H E - 4 3 - 2 D r i r T r a i n ( V A C ) M o d e l H E - 9 3 - B V a c u u m a t m o s p h e r e s C o r p o r a t i o n ; N o r t h H o l l y w o o d , C a l i f o r n i a M e t t l e r G r a m - a t i c # 1 - 9 1 1 a n d P 1 6 0 B a l a n c e s F i s h e r S c i e n t i f i c C o . ; V a n c o u v e r , B r i t i s h C o l u m b i a I R w i n d o w m a t e r i a l s ( K R S - 5 , B a F 2 , C s l , A g B r a n d A g C l ) H a r s h a w C h e m i c a l C o m p a n y ; C l e v e l a n d , O h i o 9 7 P a r m a , . O h i o . T h i s w a s u s e d f o r s y n t h e t i c p u r p o s e s . ( b ) H O P G : H i g h l y o r i e n t e d p y r o l y t i c g r a p h i t e w a s o b t a i n e d f r o m U n i o n C a r b i d e L t d . , P a r m a , O h i o . T h i s w a s u s e d t o p r e p a r e G I C s f o r e l e c t r i c a l c o n d u c t i v i t y m e a s u r e m e n t s . ( c ) N a t u r a l g r a p h i t e : N a t u r a l g r a p h i t e f l a k e s o b t a i n e d f r o m T i c o n d e r o g a a r e a i n N e w Y o r k w e r e u s e d f o r s o m e s y n t h e s e s . I I . G . P R E P A R A T I V E R E A C T I O N S . S o m e o f t h e r e a g e n t s w e r e n o t c o m m e r c i a l l y a v a i l a b l e , a n d w e r e - r p c e p a r e d a c c o r d i n g t o t h e m e t h o d s i n t h e l i t e r a t u r e . ( i ) S 2 ° 6 F 2 B i s ( f l u o r o s u l f u r y l ) p e r o x i d e , S20gF2 9 w a s p r e p a r e d b y t h e r e a c t i o n o f f l u o r i n e a n d s u l f u r t r i o x i d e a t ^ 1 8 0 ° C i n t h e 9 0 9 1 p r e s e n c e o f AgF2 c a t a l y s t ' . T h e a p p a r a t u s u s e d f o r t h i s s y n t h e s i s i s s h o w n i n F i g . 2 . 1 3 . T h e l i n e a n d t h e f l o w a p p a r a t u s w e r e b u i l t f r o m c o p p e r t u b i n g ( 1 / 4 i n c h , O . D . ) o n a m e t a l f r a m e w o r k . A l l c o n n e c t i o n s w e r e m a d e b y S w a g e l o c k f i t t i n g s . T h e p r e s s u r e o f F 2 w a s r e g u l a t e d b y A u t o c l a v e s E n g i n e e r i n g v a l v e s . F l u o r i n e w a s p a s s e d t h r o u g h a s t a i n l e s s s t e e l c y l i n d e r c o n t a i n i n g N a F t o r e m o v e H F i m p u r i t i e s . S u l f u r t r i o x i d e c o n t a i n e d i n a P y r e x f l a s k w a s c a r r i e d b y d r y N 2 t o t h e r e a c t o r w h e r e i t w a s m i x e d w i t h a s t r e a m o f F 2 • A f l u o r o l u b e o i l b u b b l e c o u n t e r w a s u s e d t o d e t e c t t h e f l o w o f e x c e s s F 2 • T h e d i m e n s i o n s o f t h e r e a c t o r a n d t h e r e a c t i o n 00 cr> To Flowmeter Copper Gloss _ l _ x ! nr To Flowmeter SOOml. Pyre* Flask Reactor (J) Whitey Valve •O" Hoke 413 Valve i f ] Autoclave Engineering Valves N o F Trop - | f 1 rTl L _ T _ J — " M • - 2 0 c m * ostjy Pr Guog* F 2 Outlet Copper t B34 B 3 4 A B B 34 C •ft -1 To cylinder To Soda - lime Trap -Fluorolube Oil Tube F I G . 2 . 1 3 Apparatus" for the Preparation of S 2 O e F2 9 9 c o n d i t i o n s w e r e m o d i f i e d f r o m t h o s e i n t h e l i t e r a t u r e . A l a r g e r r e a c t o r ( 1 2 0 e m x 7 . 6 c m ) a n d a r e a c t i o n t e m p e r a t u r e o f 1 8 0 ° C a s w e l l a s h e a t i n g t h e s u l f u r t r i o x i d e t o 5 0 ° C y i e l d e d l a r g e r q u a n t i t i e s o f t h e p r o d u c t a t a f a s t e r r a t e . T h e p r o d u c t s f o r m e d i n t h e r e a c t i o n w e r e c o n d e n s e d i n t h e c o l d -t r a p s A , B a n d C . T h e f i r s t t r a p w a s l e f t a s a n a i r c o o l e r t o a l l o w o b s e r v a t i o n a n d r e m o v a l o f p o s s i b l e n o n - v o l a t i l e s i d e p r o d u c t s . T h e l a s t t r a p w a s c o o l e d b y d r y i c e C - 7 8 ° C ) t o p r e v e n t t h e 9 1 c o n d e n s a t i o n o f t h e p o t e n t i a l l y e x p l o s i v e b y p r o d u c t F S O ^ F A s o d a l i m e f i l l e d r e a c t o r w a s u s e d t o r e n d e r e x c e s s F 2 a n d F S O ^ F i n a c t i v e . T h e c o n d e n s e d l i q u i d w a s c o l o u r l e s s , w i t h s o m e f l a k y s o l i d s o f u n r e a c t e d s u l f u r t r i o x i d e s t i l l r e m a i n i n g i n i t . T h e s e f l a k e s w e r e r e m o v e d b y w a s h i n g t h e c r u d e p r o d u c t w i t h 9 6 - 9 8 % H ^ S O ^ i n a s e p a r a t i n g f u n n e l i n t h e f u m e h o o d . T h e a b s e n c e o f F 2 o r F S O ^ F w a s i n d i c a t e d b y t h e a b s e n c e o f a n y g r e e n i s h t i n t i n t h e p r o d u c t . T h i s p r o d u c t w a s v a c u u m d i s t i l l e d i n t o P y r e x s t o r a g e v e s s e l s . I n g e n e r a l , q u a n t i t i e s o f s e v e r a l k i l o - g r a m m e s w e r e p r e p a r e d a t a t i m e a n d s t o r e d . T h e p u r i t y o f t h i s p r o d u c t w a s c h e c k e d b y g a s p h a s e I . R . 1 9 s p e c t r u m a n d F N M R o n t h e l i q u i d . ( i i ) B r O S 0 2 F B r o m i n e ( I ) f l u o r o s u l f a t e , B r O S C ^ F , w a s p r e p a r e d b y t h e d i r e c t r e a c t i o n o f B r 2 w i t h S 2 0 g F 2 a c c o r d i n g t o t h e m e t h o d 9 2 p u b l i s h e d b y A u b k e a n d G i l l e s p i e . A s l i g h t e x c e s s o f S „ 0 _ F 9 w a s u s e d t o p r e v e n t e x c e s s b r o m i n e f r o m r e m a i n i n g i n 1 0 0 t h e p r o d u c t . T h e l i q u i d w a s s t o r e d i n a P y r e x v e s s e l a n d v a c u u m d i s t i l l e d b e f o r e u s e . B r 2 + S 2 0 g F 2 2 5 ° C > 2 B r O S 0 2 F ( 2 . 1 ) ( i i i ) C 1 0 . S . 0 2 F C h l o r i n e ( I ) f l u o r o s u l f a t e , C 1 0 S 0 2 F , w a s p r e p a r e d b y r e a c t i n g C l 2 w i t h a s t o i c h i o m e t r i c a m o u n t o f S 2 0 g F 2 i n a m o n e l 9 3 m e t a l r e a c t o r . a t 1 2 5 ° C f o r 5 d a y s 1 ? R °'V C l 0 + S o 0 c F o x z s -. > 2 C 1 0 S 0 o F ( 2 . 2 ) I Z b Z Z T h e p r o d u c t w a s s t o r e d i n a m o n e l m e t a l c o n t a i n e r a n d v a c u u m d i s t i l l e d b e f o r e u s e . ( i v ) .IQS.02F I o d i n e ( I ) f l u o r o s u l f a t e , I 0 S 0 2 F , w a s p r e p a r e d b y a 9 4 s t o i c h i o m e t r i c r e a c t i o n o f w i t h S 2 0 g F 2 i i n a P y r e x r e a c t o r a t 6 0 ° C . I „ + S o 0 _ F o 6 ° ° ° > 2 I 0 S 0 o F ( 2 . 3 ) Z I b I Z T h e d a r k b r o w n l i q u i d f o r m e d a t t h i s t e m p e r a t u r e y i e l d e d a c r y s t a l l i n e p r o d u c t a t r o o m t e m p e r a t u r e . D u e t o t h e u n s t a b l e n a t u r e o f t h i s c o m p o u n d i t w a s u s e d i m m e d i a t e l y f o r i n t e r -c a l a t i o n r e a c t i o n s . 1 0 1 I I . H . ' E L E M E N T A L A N A L Y S E S C a r b o n a n d H y d r o g e n a n a l y s e s w e r e c a r r i e d o u t b y M r . P . B o r d a o f t h e C h e m i s t r y D e p a r t m e n t , T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . A C a r l o E l b a M o d e l 1 1 0 6 a n a l y z e r e m p l o y i n g a f l a s h o x i d a t i o n t e c h n i q u e w a s u s e d . T h e s a m p l e s w e r e f i r s t t r e a t e d w i t h p u r e p o w d e r e d C u O . D e t a i l s o f t h i s m e t h o d h a v e 82 b e e n p u b l i s h e d . M i c r o a n a l y s e s f o r s u l f u r , h a l o g e n s , a r s e n i c a n d a n t i m o n y w e r e p e r f o r m e d b y A n a l y t i s c h e L a b o r a t o r i e n ( f o r m e r l y A . B e r n h a r d t ) , G u m m e r s b a c h , W e s t G e r m a n y . S a m p l e s f o r m i c r o a n a l y s e s w e r e t r a n s f e r r e d i n t o g l a s s t u b e s i n t h e d r y b o x a n d f l a m e s e a l e d . 102 CHAPTER I I I GRAPHITE F L U O R O S U L F A T E S 1 0 3 C H A P T E R I I I G R A P H I T E F L U O R O S U L F A T E S I I I . A . • I N T R O D U C T I O N A c i d s a l t s o f g r a p h i t e h a v e b e e n a w i d e l y s t u d i e d g r o u p o f l a m e l l a r c o m p o u n d s . T h e i r c h e m i c a l a n d p h y s i c a l 7 8 9 p r o p e r t i e s h a v e b e e n d i s c u s s e d i n r e c e n t r e v i e w a r t i c l e s ' ' . I t h a s g e n e r a l l y b e e n a c c e p t e d t h a t m o s t o f t h e p r o t o n i c a c i d s w i t h l i t t l e o x i d i z i n g a b i l i t y d o n o t i n t e r c a l a t e i n t o g r a p h i t e t o a n y s i g n i f i c a n t e x t e n t , u n l e s s t h e g r a p h i t e l a t t i c e i s o x i d i z e d e l e c t r o c h e m i c a l l y o r b y a c h e m i c a l o x i d i z i n g a g e n t s u c h a s C r O g • E l e c t r o c h e m i c a l i n t e r c a l a t i o n o f H S O ^ F w a s 2 5 f i r s t r e p o r t e d b y U b b e l o h d e . T h e e l e c t r o l y s i s o f a n h y d r o u s H S O ^ F u s i n g g r a p h i t e a s a n o d e , a p p a r e n t l y y i e l d e d a s t a g e o n e c o m p o u n d , b u t t h i s p r o d u c t w a s n o t c h a r a c t e r i z e d f u r t h e r , d u e 9 5 t o t h e p r o b l e m s i n h a n d l i n g t h e s a m p l e . S u b s e q u e n t s t u d i e s b y H e r o l d , u s i n g c y c l i c v o l t a m e t r y a n d w e i g h t i n c r e a s e d u r i n g e l e c t r o c h e m i c a l i n t e r c a l a t i o n o f H S O g F I n t o g r a p h i t e c o n f i r m e d t h e c o m p o s i t i o n o f t h e s t a g e 1 c o m p o u n d t o b e C ^ S O ^ F ' r m H S O ^ F , w i t h m r a n g i n g f r o m 2 t o 2 . 5 . A n a t t e m p t t o I n t e r c a l a t e p u r e 4 - 9 H S O g F w i t h o u t a n y o x i d i z i n g a g e n t p r e s e n t , r e s u l t e d o n l y i n a m a t e r i a l c l a i m e d t o b e a f i f t h s t a g e c o m p o u n d w i t h a o r e p o r t e d l a y e r r e p e a t d i s t a n c e I o f 2 1 . 3 5 A . T h e s a m e 4 9 a u t h o r s r e p o r t e d t h a t t h e a d d i t i o n o f C r O ^ t o H S O g F l e d t o a s t a g e 1 i n t e r c a l a t i o n c o m p o u n d o f t h e c o m p o s i t i o n c l a i m e d o t o b e C r , H S 0 o F , w i t h a c - a x i s l a y e r r e p e a t d i s t a n c e o f 8 . 0 4 A . 5 ± 1 3 1 0 4 I t s h o u l d b e p o i n t e d o u t h o w e v e r t h a t t h i s f o r m u l a t i o n i s b a s e d o n g r a v i m e t r y a n d n o c o m p l e t e a n a l y s i s s e e m s t o h a v e 7 4 b e e n c a r r i e d o u t . A R a m a n s p e c t r u m o f t h i s c o m p o u n d w a s i n t e r p r e t e d i n t e r m s o f t i g h t l y p a c k e d a c i d m o l e c u l e s i n t h e l a m e l l a r s p a c e s . T h e f l u o r o s u l f a t e a n i o n s w h i c h a r e n e c e s s a r y t o m a i n t a i n e l e c t r i c a l n e u t r a l i t y w i t h t h e p o s i t i v e l y c h a r g e d c a r b o n l a y e r m a c r o c a t i o n s a r e h o w e v e r n o t e a s i l y d e t e c t e d b y R a m a n s p e c t r o s c o p y . T h e e x t e n t o f o x i d a t i o n o f t h e g r a p h i t e l a t t i c e b y C r 0 3 h a s n o t b e e n ' d e t e r m i n e d f o r t h i s s t a g e 1 g r a p h i t e a c i d f l u o r o s u l f a t e . B u t a n i n d i r e c t e s t i m a t i o n c a n b e m a d e b y c o m p a r i s o n w i t h g r a p h i t e a c i d t r i f l u o r o m e t h y l s u l f a t e , C ^ g S O g C F g • 1 . 6 3 H S O g C F g , p r e p a r e d i n t h e s a m e m a n n e r . H e r e , a a m a x i m u m o x i d a t i o n a m o u n t i n g t o a u n i t p o s i t i v e c h a r g e p e r 9 6 2 6 c a r b o n a t o m s w a s o b s e r v e d T h e m a j o r l i m i t a t i o n i n t h e s y n t h e s i s o f g r a p h i t e a c i d f l u o r o s u l f a t e s b y a n o d i c o r e x t e r n a l o x i d a t i o n i s t h e e x t e n t o f o x i d a t i o n o f t h e g r a p h i t e l a y e r s . T h e h i g h e s t o x i d a t i o n s t a g e c o r r e s p o n d s t o t h e f o r m a t i o n o f r e a c h e d b y e l e c t r o -l y s i s . A t t h i s s t a g e a n o x y g e n o v e r v o l t a g e i s s u p p o s e d t o b u i l d - ' u p . o n t h e a n o d e , s u p p r e s s i n g t h e f o r m a t i o n o f a h i g h e r 2 5 o x i d a t i o n s t a t e . H o w e v e r , a f i r s t s t a g e c o m p o u n d w i t h o n e p o s i t i v e c h a r g e - p e r 1 2 c a r b o n s w a s r e p o r t e d t o f o r m w h e n t h e g r a p h i t e e l e c t r o d e i s " o v e r o x i d i z e d " a t a h i g h e r p o t e n t i a l . 9 7 T h i s p h e n o m e n o n w a s f i r s t d e t e c t e d m g r a p h i t e b i s u l f a t e s O v e r o x i d a t i o n w a s s u b s e q u e n t l y f o u n d t o b e e x t e n d a b l e t o 9 5 + g r a p h i t e a c i d f l u o r o s u l f a t e s . H e r o l d r e p o r t e d t h a t a " C ^ c o m p o u n d " c a n b e s y n t h e s i z e d a c c o r d i n g t o : 105 C 2 + 4S0 3F -nHS03F — » C ^ S C ^ F - • (n-DHSOgF + H + + e (3.1) F o r m a l l y 3 o v e r o x i d a t i o n represents the conversion of a c i d mole-cules i n t o anions with .^concomitant increase i n p o s i t i v e charge without appreciable change i n mass. The presence of free a c i d molecules i n the g a l l e r i e s appears to l i m i t f u r t h e r o x i d a t i o n of the carbon l a t t i c e by reducing the number of anions that can be accomodated. The "C^, compound" formed by ov e r o x i d a t i o n showed the same d i f f r a c t o g r a m as the f i r s t stage , 95 a c i d f l u o r o s u l f a t e , but d e t a i l e d chemical analyses have not been c a r r i e d out to confirm the suggested composition. 47 Forsman et a l . proposed a method to increase, the o x i d a t i o n s t a t e of graphite i n a c i d s a l t s , termed the " i o n i c s a l t l i m i t " , by removal of the i n t e r c a l a t e d a c i d molecules i n vacuo and subsequent r e - i n t e r c a l a t i o n of the higher stage compounds thus obtained. This method does not seem s u i t a b l e f o r the graphite-HSO^F system since the vapour pressure of pure HSO^F at room temperature i s very low. Furthermore i t i s l i k e l y that HSOgF i s t i g h t l y bound to the SOgF i o n s , perhaps by H-bridges i n the l a t t i c e , which would also r e s t r i c t the usefulness of c y c l i c i n t e r c a l a t i o n technique. Since most of the I n v e s t i g a t i o n s c a r r i e d out i n these systems are d i r e c t e d towards a b e t t e r understanding of the. e f f e c t of charge t r a n s f e r on the p h y s i c a l p r o p e r t i e s of these compounds, i t i s e s s e n t i a l that a l t e r n a t e s y n t h e t i c methods be developed to reach p o s s i b l y a higher i o n i c content than the a c i d s a l t s already 1 0 6 k n o w n , f o r w h i c h t h e i n t e r c a l a t i o n o f e a c h a n i o n i s 2 5 5 1 9 5 a c c o m p a n i e d b y 2 t o 3 m o l e c u l e s o f t h e f r e e a c i d ' ' T h e s t u d i e s o n b i n a r y a n d a c i d f l u o r o s u l f a t e s d e s c r i b e d i n t h i s c h a p t e r w e r e c a r r i e d o u t w i t h t w o m a i n o b j e c t i v e s : ( i ) t o s y n t h e s i z e b i n a r y g r a p h i t e f l u o r o s u l f a t e s o f t h e t y p e C + S 0 „ F w h i c h e s s e n t i a l l y c o u l d i n c r e a s e t h e J r n 3 J c h a r g e t r a n s f e r f a c t o r t o t h e m a x i m u m p o s s i b l e v a l u e o f 1 . 0 , a n d ( i i ) t o d e v e l o p s y n t h e t i c m e t h o d s t o i n t e r c a l a t i o n c o m p o u n d s c o n t a i n i n g c o n t r o l l e d a m o u n t s o f f l u o r o s u l f a t e a n i o n a n d t h e f r e e a c i d . T h e s e s y n t h e t i c a t t e m p t s a r e e x p e c t e d t o e s t a b l i s h a c o m m o n l i n k b e t w e e n t h e b i n a r y f l u o r o s u l f a t e s , C + S 0 o F , a n d t h e a c i d f l u o r o s u l f a t e s , n o C : + S 0 o F - m H S O - F . I n a d d i t i o n , t h i s c o u l d l e a d t o a n o d b e t t e r u n d e r s t a n d i n g o f t h e p a c k i n g o f f r e e a c i d m o l e -c u l e s l i k e H S O ^ F i n t h e l a t t i c e f o r w h i c h n o c l e a r i d e a s h a v e e m e r g e d u p t o n o w . T h e s y n t h e s i s o f b i n a r y f l u o r o s u l f a t e s b y t h e o x i d a t i o n 2 8 o f g r a p h i t e b y S 2 0 g F 2 w a s f i r s t u n d e r t a k e n b y B a r t l e t t e t a l . , a n d a f i r s t s t a g e c o m p o u n d f o r m u l a t e d a s C g S O ^ F w a s o b t a i n e d . 8 0 I n a m o r e r e c e n t s t u d y o f t h e g a s p h a s e i n t e r c a l a t i o n o f S 2 0 g F 2 i n t o v a r i o u s t y p e s o f g r a p h i t e a l i m i t i n g c o m p o s i t i o n o f C ^ S O g F w a s s u g g e s t e d . T h e u s e f u l n e s s o f b i s ( f l u o r o s u l f u r y D p e r o x i d e S 2 0 g F 2 , a s a n o x i d a t i v e i n t e r c a l e n t c a n b e i l l u s t r a t e d b y t h e f o l l o w i n g f a c t s : 1 0 7 B i s ( f l u o r o s u l f u r y l ) p e r o x i d e i s a r a t h e r v e r s a t i l e o x i d i z e r . W i t h i t s m o l e c u l a r s t r u c t u r e p r e s u m e d t o 9 8 b e o f C 2 s y m m e t r y , i t i s b e s t v i e w e d a s a s y m m e t r i c a l c o m b i n a t i o n o f t w o f l u o r o s u l f a t e r a d i c a l s v i a a w e a k 0 - 0 b o n d a s s h o w n b e l o w ; 0 0 F S 0 0 S F 0 0 i n g o o d a n a l o g y w i t h t h e d i h a l o g e n m o l e c u l e s . T h e r u p t u r e o f t h e r e l a t i v e l y w e a k p e r o x y l i n k a g e i n t o t w o f r e e r a d i c a l s i s e a s i l y a c c o m p l i s h e d , a n d t h e e x i s t e n c e o f t h e f l u o r o s u l f a t e r a d i c a l i n e q u i l i b r i u m w i t h i t s d i m e r h a s b e e n f i r s t s u g g e s t e d f r o m t h e r e v e r s i b l e a p p e a r a n c e o f a y e l l o w c o l o r a t i o n w h e n S^O^T^ i s h e a t e d S o 0 „ F o ^ 2 S 0 o F ' ( 3 . 2 ) 9 9 D u d l e y a n d C a d y , w h o a l s o f i r s t s y n t h e s i z e d S 2 0 g F 2 f r o m S O g a n d T ~ ^ ^ ^ h a v e s h o w n e v i d e n c e f o r t h i s e q u i l i b r i u m b y m e a s u r i n g t h e t e m p e r a t u r e d e p e n d e n c e o f t h e p r e s s u r e a t c o n s t a n t v o l u m e b e t w e e n 4 5 0 K a n d 6 0 0 K , a n d t h e t e m p e r a t u r e d e p e n d e n c e o f t h e a b s o r p t i o n o f t h e f l u o r o s u l f a t e r a d i c a l a t 4 4 7 n m . T h e e n t h a l p y o f d i s s o c i a t i o n o f S „ 0 _ F _ i n t o t w o f r e e r a d i c a l s h a s b e e n z b / e s t i m a t e d t o b e 9 2 . 1 k J / m o l a n d 9 7 . 6 k J / m o l b y t h e s e 1 0 1 t w o m e t h o d s r e s p e c t i v e l y . A k i n e t i c s t u d y o n t h i s e q u i l i b r i u m h a s d e t e r m i n e d t h e e n t h a l p y o f d i s s o c i a t i o n 1 0 8 t o b e 9 1 . 3 k j / m o l a n d s i m i l a r v a l u e s a r e f o u n d f r o m t e m p e r a t u r e d e p e n d e n t E S R m e a s u r e m e n t s o n t h e S O ^ F * 1 0 2 r a d i c a l . T h e e l e c t r o n a f f i n i t y o f t h i s r a d i c a l 1 0 3 a p p e a r s t o b e r a t h e r h i g h . T h i s v e r y h i g h e l e c t r o n a f f i n i t y o f t h e f r e e r a d i c a l m a k e s S o 0 _ F o a f a v o r a b l e z fa I o x i d a t i v e i n t e r c a l a n t w h i c h c o u l d a b s t r a c t e l e c t r o n s f r o m t h e i T - e l e c t r o n c l o u d o f g r a p h i t e a c c o r d i n g t o : S o 0 c F o + 2 e y 2 S 0 Q F ( 3 . 3 ) z b z 3 f o r m i n g a v e r y s t a b l e f l u o r o s u l f a t e a n i o n w h i c h c o u l d b e i n t e r c a l a t e d i n t o g r a p h i t e i n t h e p r o c e s s . T h e s a m e r e a g e n t f u n c t i o n i n g a s o x i d i z i n g a g e n t a n d i n t e r -c a l a n t a v o i d s t h e u s e o f a f o r e i g n o x i d i z i n g a g e n t o r t h e i n v o l v e m e n t o f e l e c t r o c h e m i c a l m e t h o d s . 1 0 4 T h e r e a r e h o w e v e r p r e c e d e n t s , w h e r e S o 0 n F „ • z b z m a y i n i t i a t e e i t h e r f l u o r i d e o r o x i d e f o r m a t i o n , p r e s u m a b l y v i a t h e r m a l d e c o m p o s i t i o n o f S O ^ F - g r o u p s a c c o r d i n g t o t w o g e n e r a l s c h e m e s : E ( S 0 o F ) * - E F + n S 0 o ( 3 . 4 ) 3 n n 3 o r E ( S 0 „ F ) * • E O , + n / o S o 0 c F o ( 3 . 5 ) 3 n ' 2 2 5 2 w i t h f l u o r i d e s o r m i x e d f l u o r i d e - f l u o r o s u l f a t e s i n o n e c a s e a n d o x i d e s o r o x y f i u o r o s u l f a t e s i n t h e o t h e r , a s p o s s i b l e r e a c t i o n p r o d u c t s . T h e s e s i d e r e a c t i o n s h a v e i n v o l v e d p r i m a r i l y h i g h v a l e r i t m e t a l o r n o n m e t a l . ~ d e r i v a t i v e s , a n d h a v e , w h e r e i o n i c f l u o r o s u l f a t e s u n d e r -1 0 9 w e n t s u c h d e c o m p o s i t i o n s , i n v o l v e d r a t h e r h i g h t e m p e r -a t u r e s . A t o r d i n a r y i n t e r c a l a t i o n t e m p e r a t u r e s t h e p o s s i b i l i t i e s o f f l u o r i n a t i o n o f t h e g r a p h i t e l a t t i c e b y S 2 0 g F 2 a r e e x t r e m e l y r e m o t e a n d p l a n a r i t y o f t h e c a r b o n l a y e r s s h o u l d b e r e t a i n e d . ( i i ) T h e p h y s i c a l p r o p e r t i e s o f S 2 0 g F 2 , w h i c h i s a l o w b o i l i n g l i q u i d ( s e e t a b l e 3 . 1 ) e n a b l e t h e t r a n s f e r o f t h i s l i q u i d i n t o t h e r e a c t o r c o n t a i n i n g g r a p h i t e , a s w e l l a s t h e r e m o v a l o f e x c e s s r e a g e n t a f t e r t h e r e a c t i o n , u s i n g s t a n d a r d v a c u u m l i n e t e c h n i q u e s . T h i s r e a g e n t s e e m s l e s s c o r r o s i v e t h a n H S O ^ F a n d p e r m i t s t h e u s e o f g l a s s a p p a r a t u s t h r o u g h o u t , w i t h g l a s s a t t a c k o n l y n o t e d o n p r o l o n g e d e x p o s u r e s a t t e m p e r a t u r e s a b o v e 1 0 0 ° C . T h e c o n v e r s i o n o f a c i d f r e e s a l t s , C S 0 „ F t o a c i d s a l t s , n 3 C ^ S Q g F ' m H S O g F m a y i n v o l v e a n y o f t h r e e p o s s i b l e r o u t e s : ( i ) t h e r e a c t i o n o f b i n a r y g r a p h i t e f l u o r o s u l f a t e s w i t h H S O ^ F m i g h t p o s s i b l y i n v o l v e p r o t o n m i g r a t i o n f r o m t h e a c i d t o t h e i n t e r c a l a t e , o r c o n v e r s e l y t h e s u b s t i t u t i o n o f i n t e r c a l a t e d f l u o r o s u l f a t e g r o u p , a s S O ^ F o r a s S O ^ F ' r a d i c a l t o c o m b i n e t o f o r m S 2 0 g F 2 , b y f r e e a c i d m o l e c u l e s . ( i i ) t h e a d d i t i o n o f H S O g F t o h i g h e r s t a g e b i n a r y g r a p h i t e f l u o r o s u l f a t e s , o r ( i i i ) t h e u s e o f m i x t u r e s o f S o 0 _ F o a n d H S 0 o F f o r s i m u l t a n e o u s z b z o i n t e r c a l a t i o n o f S O g F - a n d H S O ^ F . 1 1 0 T A B L E 3 . 1 : S O M E P H Y S I C A L P R O P E R T I E S O F H S 0 o F , S o 0 F o Z b Z C o m p o u n d H S 0 3 F 8 9 S 2 ° 6 F 2 1 0 5 b o i l i n g p o i n t (. ° C ) + 1 6 2 . 7 + 6 7 . 1 m e l t i n g p o i n t ( ° C ) 8 8 . 9 8 - 5 5 . 4 d e n s i t y ( g m / c m ) 1 . 7 2 6 @ 2 5 ° C 1 . 6 4 5 @ 3 5 . 5 ° C v i s c o s i t y ( c e n t i p o i s e ) 1 . 5 6 @ 2 5 ° C s p e c i f i c c o n d u c t a n c e (Q 1 c m 1 ) 1 . 0 8 x 1 0 @ 2 5 ° C - 4 v a p o u r p r e s s u r e e q u a t i o n l o g P = 5 . 4 9 9 1 6 6 m m • 1 . 2 9 2 5 x T O ' T ( K ) I l l T h e f r e e a c i d m o l e c u l e s a r e s o m e t i m e s v i e w e d a s c o -10 6 i n t e r c a l a t e s d u r i n g o x i d a t i o n w h i c h a r e r a t h e r u n n e c e s s a r y i n t h e g a l l e r i e s a n d s o m e t i m e s v i e w e d a s e s s e n t i a l s p a c e r s t o d i m i n i s h a n i o n - a n i o n r e p u l s i o n a n d t o f a c i l i t a t e c h a r g e 1 0 7 d i s t r i b u t i o n m t h e i n t e r c a l a t e l a y e r . A n i n v e s t i g a t i o n o f t h e s e p r o d u c t s b y s o l i d s t a t e N M R a n d e l e c t r i c a l c o n d u c t a n c e m e a s u r e m e n t s i n H S O g F s h o u l d s h e d s o m e l i g h t o n t h e n a t u r e o f t h e s e a c i d f l u o r o s u l f a t e s . I I I . B . B I N A R Y G R A P H I T E F L U O R O S U L F A T E S I I I . B . 1 S Y N T H E T I C R O U T E S T O B I N A R Y G R A P H I T E F L U O R O S U L F A T E S S y n t h e s e s o f b i n a r y g r a p h i t e f l u o r o s u l f a t e s w e r e a t t e m p t e d v i a l i q u i d p h a s e a n d v a p o u r p h a s e i n t e r c a l a t i o n m e t h o d s . ( a ) L I Q U I D P H A S E I N T E R C A L A T I O N T h e o x i d a t i v e i n t e r c a l a t i o n o f g r a p h i t e , b o t h H O P G a n d S P 1 p o w d e r , w a s c a r r i e d o u t a t r o o m t e m p e r a t u r e b y a l l o w i n g a p p r o x i m a t e l y 1 0 0 - 2 0 0 m g o f g r a p h i t e t o r e a c t w i t h a l a r g e e x c e s s ( a b o u t 1 0 m l ) o f l i q u i d S 2 0 g F 2 f o r a p p r o x i m a t e l y 4 8 h o u r s w i t h m a g n e t i c s t i r r i n g . E x c e s s o f S 2 0 g F 2 w a s r e m o v e d i n v a c u o a n d t h e p r o d u c t w a s m a i n t a i n e d i n a d y n a m i c v a c u u m u n t i l c o n s t a n t w e i g h t w a s r e a c h e d . A d a r k b l u e p o w d e r y p r o d u c t w a s o b t a i n e d . T h i s s a m p l e w a s s u b j e c t e d t o m i c r o -a n a l y s e s . S i n c e t h e r e a c t i o n w a s c a r r i e d o u t u s i n g l i q u i d i n t e r -1 1 2 c a l a n . t t h e p o s s i b i l i t i e s o f . c a p i l l a r y c o n d e n s a t i o n a n d s u r f a c e a d s o r p t i o n o f t h e i n t e r c a l a n t w e r e e x p e c t e d . S a m p l e s o f c o m p o s i t i o n s ^ C g S O ^ F ( a c c o r d i n g t o w e i g h t i n c r e a s e ) s h o w e d 1 9 . . a w e a k F N M R r e s o n a n c e a t 4 0 p p m r e l a t i v e t o C F C l g m a d d i t i o n t o t h e s t r o n g s i g n a l a t 1 2 . 1 p p m a s s h o w n i n f i g . ( 3 . 1 ) O n p r o l o n g e d p u m p i n g t h e w e a k s i g n a l d i s a p p e a r e d . T h i s r e s o n a n c e w a s a t t r i b u t e d t o e i t h e r s u r f a c e a d s o r b e d o r c a p i l l a r y c o n d e n s e d S^O^F^ o n t h e b a s i s o f t h e h i g h r e s o l u t i o n 1 0 8 N M R c h e m i c a l s h i f t v a l u e o f 4 0 . 4 p p m r e p o r t e d f o r S 2 0 g F 2 . T h e s a m p l e r e a c h e d c o n s t a n t w e i g h t a f t e r t h e r e m o v a l o f a l l e x c e s s S o 0 r F „ , a n d m i c r o a n a l y s i s a s w e l l a s g r a v i m e t r i c r e s u l t s / b I a g r e e d w i t h a c o m p o s i t i o n o f ^ C ^ S O ^ F . D u r i n g t h i s r e a c t i o n , t h e v a p o u r s o v e r t h e r e a c t i o n m i x t u r e w e r e c h e c k e d b y I . R . 9 8 s p e c t r o s c o p y w h i c h i d e n t i f i e d S 2 0 g F 2 a s t h e s o l e c o n s t i t u e n t i n t h e v a p o u r s r u l i n g o u t t h e p o s s i b i l i t y o f d e c o m p o s i t i o n o f S 2 0 g F 2 d u r i n g t h e r e a c t i o n t o f o r m S 2 ° 5 ' F 2 ' S ° 2 F 2 e " t c " A l s o p r e s s u r e m e a s u r e m e n t s o v e r t h e r e a c t i o n m i x t u r e a t l i q u i d N 2 t e m p e r a t u r e r u l e d o u t t h e f o r m a t i o n o f n o n - c o n d e n s i b l e g a s e s s u c h a s 0 2 d u r i n g t h e r e a c t i o n . S o m e o f t h e s a m p l e s o f C ^ S O ^ F p r e p a r e d f r o m S P 1 p o w d e r w e r e s u s p e n d e d i n a n e x c e s s o f H S O g F f o r 2 4 h o u r s a n d s u b s e q u e n t l y d r i e d i n v a c u o . T h e s e s a m p l e s w e r e f o u n d t o b e e s s e n t i a l l y u n c h a n g e d i n t h e i r c o m p o s i t i o n a f t e r t h i s t r e a t m e n t w i t h H S O g F . S o m e t y p i c a l c o m p o s i t i o n s o b s e r v e d i n t h e p r o d u c t s o f t h e a b o v e r e a c t i o n s a r e l i s t e d i n T a b l e ( 3 . 2 ) . H y d r o g e n w a s n o t d e t e c t e d b y m i c r o a n a l y s i s i n a n y o f t h e s e s a m p l e s . S h o r t e r r e a c t i o n t i m e s f o r b o t h S P 1 p o w d e r a n d H O P G p i e c e s 113 O1 50* 100^ 1 1 4 T A B L E . 3 . 2 ; C O M P O S I T I O N S . O F B I N A R Y G R A P H I T E F L U O R O S U L F A T E S O B T A I N E D B Y L I Q U I D P H A S E I N T E R C A L A T I O N . S a m p l e C o m p o s i t i o n % C C o n t e n t I ( A ) S t a g e G r a v i m e t r y M i c r o a n a l y s i s ( o b s e r v e d ) ( i ) C „ r n S 0 „ F C 7 n , , S 0 Q F 4 6 . 0 5 7 . 8 1 + 0 . 0 3 1 / . b U 3 / . U 4 6 ( i i ) C „ C Q S O Q F C „ n c S 0 o F 4 6 . 1 2 7 . 8 1 1 0 . 0 3 1 /.bo d / . U b 3 ( i i i ) a C ^ c c S 0 o F Cn - , „ S 0 o F 4 6 . 4 0 7 . 8 1 1 0 . 0 3 1 a S a m p l e ( i i i ) w a s o b t a i n e d b y t r e a t i n g s a m p l e ( i i ) w i t h H S 0 o F a s d e s c r i b e d i n s e c t i o n I I I . B . l ( a ) . 1 1 5 r e s u l t e d i n t h e f o r m a t i o n o f a c o m p o u n d o f a p p r o x i m a t e c o m p o s i t i o n C - ^ S O g F a s e v i d e n c e d b y g r a v i m e t r y a n d m i c r o a n a l y s i s ( % ' C = 5 8 . 8 7 ) . X - r a y p o w d e r d i f f r a c t i o n o f c o m p o u n d s ( i ) - ( i i i ) i n T a b l e ( 3 . 2 ) s h o w e d l i n e s d u e t o ( 0 0 1 ) , ( 0 0 2 ) , ( 0 0 3 ) a n d * ( 1 0 0 ) p l a n e s . T h e f i r s t t h r e e l i n e s a r e a s s o c i a t e d w i t h i n -p l a n e h e x a g o n a l n e t w o r k o f c a r b o n a t o m s , t h e ( 0 0 2 ) l i n e w a s o f t h e h i g h e s t i n t e n s i t y c o n f i r m i n g t h a t t h e s e c o m p o u n d s w e r e p r i m a r i l y o f s t a g e 1 c o m p o s i t i o n w i t h a n i n t e r l a y e r s e p a r a t i o n o o f 7 . 8 1 ± 0 . 0 3 A . T h i s w a s s u p p o r t e d b y t h e p o s i t i o n o f t h e E _ 0 v i b r a t i o n a l m o d e o f t h e s e c o m p o u n d s o b s e r v e d a t 1 6 3 6 c m ^ 2 g 2 i n t h e i r R a m a n s p e c t r a . S e v e r a l a t t e m p t s w e r e m a d e t o e x t e n d t h i s l i q u i d p h a s e r e a c t i o n t o t h e s y n t h e s i s o f h i g h e r s t a g e g r a p h i t e f l u o r o -s u l f a t e s . R e a c t i o n s w e r e c a r r i e d o u t e i t h e r b y l i m i t i n g t h e a m o u n t o f ^ O ^ F ^ ^ a d d e d t o g r a p h i t e , o r b y l i m i t i n g t h e r e a c t i o n t i m e s . B o t h o f t h e s e m e t h o d s y i e l d e d p r o d u c t s w h i c h w e r e m i x t u r e s o f d i f f e r e n t s t a g e s d u e t o i n c o m p l e t e r e a c t i o n . T h e r e f o r e t h e l i q u i d p h a s e r e a c t i o n i s s u i t a b l e o n l y f o r t h e s y n t h e s i s o f t h e s t a g e 1 c o m p o u n d C ^ S O ^ F a n d m e t h o d s h a v e t o b e d e v e l o p e d t o s y n t h e s i z e h i g h e r s t a g e m a t e r i a l s . ( b ) V A P O U R P H A S E I N T E R C A L A T I O N V a p o u r p h a s e i n t e r c a l a t i o n c a n b e c a r r i e d o u t u s i n g t w o d i f f e r e n t e x p e r i m e n t a l a p p r o a c h e s : ( i ) I n t e r c a l a t i o n a t c o n t r o l l e d p r e s s u r e : T h e r e a c t i o n c a n b e c o n t r o l l e d b y l i m i t i n g t h e p r e s s u r e o f S o 0 _ F „ o v e r g r a p h i t e . H e n c e t h e r e a c t i o n c a n b e t e r m i n a t e d 2 6 2 1 1 6 w h e n t h e w e i g h t i n c r e a s e i n t h e s a m p l e i n d i c a t e s a c o m p o s i t i o n c o r r e s p o n d i n g t o t h e h i g h e r s t a g e c o m p o u n d r e q u i r e d . ( i i ) I n t e r c a l a t i o n u s i n g c o n t r o l l e d a m o u n t o f i n t e r c a l a n t : I n t h i s m e t h o d , g r a p h i t e c a n b e e x p o s e d t o a c o n t r o l l e d a m o u n t o f S^O^F^ v a p o u r s i n a s e a l e d r e a c t o r , s o t h a t w h e n a n e q u i l i b r i u m i s r e a c h e d t h e c o m p o s i t i o n o f t h i s s a m p l e w o u l d b e o f t h e r e q u i r e d s t a g e . T h e c o n t r o l l e d p r e s s u r e m e t h o d w a s a d o p t e d i n t h i s s t u d y t o s y n t h e s i z e G I C s . T h e v a r i a t i o n o f t h e v a p o u r p r e s s u r e o f S ^ O g F ^ w i t h t e m p e r a t u r e h a s b e e n p u b l i s h e d " ^ ^ . A t r o o m t e m p e r a -t u r e t h e v a p o u r p r e s s u r e o f t h i s l i q u i d i s ^ 1 5 0 T o r r , a n d i t d r o p s t o ^ 5 0 T o r r a t 0 ° C . T h e r e f o r e s u f f i c i e n t v a p o u r r p r e s s u r e o f t h i s r e a g e n t c a n b e o b t a i n e d b y c o n t r o l l i n g t h e t e m p e r a t u r e o f t h e b u l k i n t e r c a l a n t . T h i s m e t h o d w a s f o u n d t o b e s u i t a b l e f o r t h e s y n t h e s i s o f s a m p l e s o f s t a g e s o n e a n d t w o . A t t e m p t s t o s y n t h e s i z e s a m p l e s o f h i g h e r s t a g e s r e s u l t e d i n m i x t u r e s o f s e v e r a l s t a g e s . X - r a y p o w d e r d i f f r a c t i o n o f t h e s e s a m p l e s s h o w e d t h e p r e s e n c e o f t h e s t a g e 2 c o m p o u n d a l o n g w i t h h i g h e r s t a g e s . S Y N T H E S I S O F A S T A G E 1 G R A P H I T E F L U O R O S U L F A T E B Y C O N T R O L L E D P R E S S U R E M E T H O D I n a t y p i c a l r e a c t i o n a b o u t 2 0 0 m g o f g r a p h i t e p o w d e r w e r e e x p o s e d t o S 2 0 g F 2 v a p o u r a t r o o m t e m p e r a t u r e f o r s e v e r a l h o u r s . T h e s a m p l e w a s o c c a s i o n a l l y s t i r r e d t o e n s u r e u n i f o r m e x p o s u r e t o t h e i n t e r c a l a n t v a p o u r . T h e s a m p l e w a s t h e n 1 1 7 e v a c u a t e d t o r e m o v e a n y . c o n d e n s e d l i q u i d a n d r e a c t e d a g a i n w i t h ^ 2 ^ 6 ^ 2 v a P o u r > T h i s p r o c e d u r e w a s r e p e a t e d u n t i l t h e s a m p l e r e a c h e d c o n s t a n t w e i g h t . X - r a y d i f f r a c t i o n o n t h i s s a m p l e c o n f i r m e d i t t o b e a s t a g e 1 c o m p o u n d w h i l e i n c r e a s e i n w e i g h t s u g g e s t e d a c o m p o s i t i o n o f 2 ^ 0 ^ . M i c r o a n a l y s i s i n d i c a t e d a c o m p o s i t i o n o f C 7 ^ S O g F ( % C o b s e r v e d = 4 - 6 . 2 5 ) . S Y N T H E S I S O F A S T A G E 2 G R A P H I T E F L U O R O S U L F A T E B Y T H E C O N T R O L L E D P R E S S U R E M E T H O D I n a t y p i c a l r e a c t i o n a b o u t 2 0 0 m g o f g r a p h i t e p o w d e r w e r e e x p o s e d t o ^2(~>B^2 v a P o u r ^ o r a b o u t 6 0 m i n u t e s . T h e v a p o u r p r e s s u r e o f S 2 0 g F 2 w a s m a i n t a i n e d a t ^ 5 0 T o r r b y l o w e r i n g t h e t e m p e r a t u r e o f t h e l i q u i d r e s e r v o i r t o 0 ° C . T h e w e i g h t o f t h e p r o d u c t w a s c h e c k e d i n b e t w e e n e v a c u a t i o n s a n d t h e a d d i t i o n s o f f r e s h v a p o u r . T h e r e a c t i o n w a s s t o p p e d w h e n , t h e s a m p l e r e a c h e d t h e w e i g h t c h a n g e a f t e r e v a c u a t i o n c o r r e s -p o n d i n g t o a c o m p o s i t i o n o f % C ^ S O ^ F . M i c r o a n a l y s i s o n t h i s p a l e b l u e s a m p l e s u g g e s t e d a c o m p o s i t i o n o f C ^ 2 ^ 0 ^ ( % C o b s e r v e d = 6 3 . 2 5 ) . X - r a y p o w d e r d i f f r a c t i o n o f t h i s s a m p l e s h o w e d l i n e s d u e t o ( 0 0 1 ) , ( 0 0 3 ) a n d ( 0 0 4 ) p l a n e s . T h e m a x i m u m i n t e n s i t y o f t h e ( 0 0 3 ) l i n e s h o w e d t h a t t h e s a m p l e w a s p r i m a r i l y o f s t a g e 2 c o m p o s i t i o n . T h e l a y e r r e p e a t d i s t a n c e o I w a s c a l c u l a t e d t o b e 1 1 . 1 6 ± 0 . 0 3 A . T h e p o s i t i o n o f E „ „ c ^ 2 g 2 v i b r a t i o n a l m o d e o f t h i s s a m p l e a t 1 6 2 1 c m 1 i n i t s R a m a n s p e c t r u m a l s o s u g g e s t e d t h e s a m p l e t o b e p r i m a r i l y o f s t a g e 2 c o m p o s i t i o n . 1 1 8 I I I . B . 2. T H E R M A L D E C O M P O S I T I O N S T U D Y . O N S T A G E 1 B I N A R Y G R A P H I T E F L U O R O S U L F A T E T h i s s t u d y w a s c a r r i e d o u t t o i d e n t i f y t h e t h e r m a l d e c o m p o s i t i o n p r o d u c t s o f C ^ ^ ^ S O ^ F w i t h i n t h e t e m p e r a t u r e r a n g e 2 5 - 2 0 0 ° C . T h e a p p a r a t u s u s e d f o r t h i s s t u d y i s s h o w n i n F i g . 3.2. A b o u t 5 0 0 m g o f t h e g r a p h i t e f l u o r o s u l f a t e , C y 2SO.3F m a d e f r o m SP1 p o w d e r w e r e t a k e n i n t h e E r l e n m e y e r f l a s k . T h e s a m p l e w a s s p r e a d o n t h e f l a t b o t t o m o f t h e f l a s k t o e n s u r e u n i f o r m h e a t i n g . T e m p e r a t u r e o f t h e o i l b a t h w a s c o n t r o l l e d b y a c o n t a c t t h e r m o m e t e r ( S G A S c i e n t i f i c I n c . m o d e l FW21, 0 - 3 0 0 ° C ) . T h e a p p a r a t u s w a s e v a c u a t e d a t 2 5 ° C a n d t h e t e m p e r a t u r e o f t h e b a t h w a s i n c r e a s e d w h i l e t h e l i q u i d N ^ c o o l e d t r a p r e m a i n e d c l o s e d . T h e b a t h t e m p e r a t u r e w a s c h a n g e d b y i n c r e m e n t s o f 5 ° C , a n d t h e s a m p l e w a s m a i n t a i n e d a t e a c h t e m p e r a t u r e f o r s u f f i c i e n t t i m e s o t h a t a c o n s t a n t v a p o u r p r e s s u r e w a s m a i n -t a i n e d . A f t e r r e c o r d i n g t h e p r e s s u r e t h e l i q u i d N ^ c o o l e d t r a p w a s o p e n e d a n d t h e v a p o u r c o n d e n s e d r a p i d l y . T h e v a p o u r p r e s s u r e o v e r t h e s a m p l e i n c r e a s e d i n t h e t e m p e r a t u r e r a n g e 5 0 - 8 0 ° C . T h e l i q u i d o b t a i n e d b y c o n d e n s i n g t h e d e i n t e r c a l a t e d m a t e r i a l i n t h i s t e m p e r a t u r e r a n g e w a s a n a l y z e d b y R a m a n S p e c t r o s c o p y . R a m a n s p e c t r u m o f t h i s l i q u i d w a s i d e n t i c a l t o 9 8 t h e s p e c t r a r e p o r t e d f o r S 2 0 g F 2 . V e r y s m a l l v a p o u r p r e s s u r e i n c r e a s e s w e r e o b s e r v e d i n . t h e t e m p e r a t u r e r a n g e 8 0 - 1 2 0 ° C . T h e v a p o u r p r e s s u r e i n c r e a s e d s t e a d i l y a f t e r t h i s , a n d t h e I . R . s p e c t r a o f t h e v a p o u r s c o l l e c t e d s h o w e d t h e p r e s e n c e o f S 2 ° 6 F 2 9 8 a n d s i F 4 . 1 0 9 - H e a t i n g w a s s t o p p e d w h e n t h e b a t h . 1 1 9 To Vacuum F I G . 3 . 2 A P P A R A T U S U S E D F O R T H E R M A L D E C O M P O S I T I O N S T U D I E S 1 2 0 t e m p e r a t u r e r e a c h e d 2 0 0 ° C . T h r o u g h o u t t h e t e m p e r a t u r e r a n g e 2 5 - 2 0 0 ° C t h e d e i n t e r c a l a t e d v a p o u r s w e r e f o u n d t o b e p r i m a r i l y ^ 2 ^ 6 ^ * 2 ' ^ l F 4 m ^ S h t h a v e b e e n p r o d u c e d d u e t o t h e r e a c t i o n o f ^ 2 ^ 6 ^ 2 v a P o u r w i t h t h e P y r e x a p p a r a t u s a t t h e h i g h e r t e m p e r a -t u r e s ( 1 2 0 - 2 0 0 ° C ) . B i s ( f l u o r o s u l f u r y D p e r o x i d e h a s b e e n 9 9 r e p o r t e d t o r e a c t w i t h q u a r t z c e l l s a t t e m p e r a t u r e s a b o v e 1 2 0 ° C . I n n o n e o f t h e s t a g e s o f t h e r m a l d e c o m p o s i t i o n i n t h e s t u d y o f g r a p h i t e f l u o r o s u l f a t e , o x y g e n o r a n y o t h e r u n c o n d e n -s i b l e g a s w a s l i b e r a t e d f r o m t h e s a m p l e . T h e r e s i d u e c o m p o u n d 1 9 a f t e r h e a t i n g t o 2 0 0 ° C w a s a n a l y z e d b y F N M R a n d a b r o a d s i g n a l w a s o b s e r v e d a t ^ 1 0 p p m r e l a t i v e t o C F C l g . T h i s s i g n a l w a s a t t r i b u t e d t o i n t e r c a l a t e d S O ^ F . T h e a b s e n c e o f o t h e r f l u o r i n e r e s o n a n c e s , f o r e x a m p l e , i n t h e C - F r e g i o n S ' h o w e d t h a t S o 0 r F o d i d n o t f l u o r i n a t e t h e c a r b o n p l a n e s o f t h e g r a p h i t e 2 6 2 l a t t i c e , e v e n a t 2 0 0 ° C t o a n y d e t e c t a b l e e x t e n t . T h e i n t e r -c a l a t e d S O - F i o n s a r e t h e r e f o r e d e i n t e r c a l a t e d a s S _ 0 r F o 3 z b z w i t h o u t a n y e x t e n s i v e r e a c t i o n w i t h t h e h o s t m a t e r i a l . H o w e v e r , t h i s e x p e r i m e n t i s p r i m a r i l y q u a l i t a t i v e . T h e 9 9 e x t e n t o f d i s s o c i a t i o n a c c o r d i n g t o e q u a t i o n ( 3 . 2 ) i s k n o w n t o i n c r e a s e w i t h t e m p e r a t u r e a n d s h o u l d a f f e c t t h e m e a s u r e d v a p o u r p r e s s u r e o v e r t h e s a m p l e . T h e r a p i d d e c r e a s e i n v a p o u r p r e s s u r e i n t h e r a n g e 8 0 - 1 2 0 ° C s h o w s t h a t t h e i n t e r -c a l a t i o n c o m p o u n d r e a c h e s a s t a b l e c o m p o s i t i o n a r o u n d 8 0 ° C . T h i s m a y b e d u e t o t h e c o m p l e t e t r a n s f o r m a t i o n o f t h e s t a g e 1 c o m p o u n d t o a s e c o n d o r e v e n h i g h e r s t a g e m a t e r i a l a c c o r d i n g t o : 2 C „ S 0 o F y C , . . S O - F + - ( S o 0 „ F „ ) ( 3 . 6 ) 7 3 1 4 d o z b z 1 2 1 T h e f o r m a t i o n o f b i s C f l u o r o s u l f u r y i ) p e r o x i d e b y p y r o l y s i s o f f l u o r o s u l f a t e s h a s a l i m i t e d n u m b e r o f p r e c e d e n t s . D e c o m p o s i -t i o n o f X e ( S 0 3 F ) 2 a c c o r d i n g t o E q u a t i o n 3 . 7 i s u s e d b y X e ( S 0 „ F ) o > - X e + S o 0 c F o ( 3 . 7 ) 6 Z I b 2 B a r t l e t t 1 1 0 i n t h e s y n t h e s i s o f S ^ F ^ P d i : C P d I V ( S 0 3 F ) 1 1 1 u n d e r g o e s t h e f o l l o w i n g " r e a c t i o n w h e n h e a t e d t o 1 6 0 ° C . P d I : C P d I V ( S 0 o F ) c 1 6 ° ° C " ) " 2 P d ( S 0 „ F ) o + S o 0 K F o ( 3 . 8 ) 3 6 3 2 2 6 2 T h e d e c o m p o s i t i o n o f A g ( S 0 3 F ) 2 a l s o l i b e r a t e s s 2 0 g F 2 a c c o r d i n g t o " ^ 3 e q u a t i o n ( 3 . 9 ) . 2 A g ( S 0 3 F ) 2 2 5 ° ° C ) 2 A g S 0 3 F + S2°ZY2 ( 3 . 9 ) T h e m e t a l f l u o r o s u l f a t e s o f s i l v e r a n d p a l l a d i u m o f f e r a c e r t a i n p a r a l l e l t o t h e b e h a v i o u r o f C ^ S O g F , a s i n a l l i n s t a n c e s l o w e r v a l e n t f l u o r o s u l f a t e s a r e f o r m e d r a t h e r t h a n f l u o r i d e o r o x i d e f l u o r o s u l f a t e s . I I I . B . 3 E L E C T R I C A L C O N D U C T A N C E M E A S U R E M E N T S O N S U S P E N S I O N S O F C 7 S . 0 3 F . . I N . H S O g F M a n y m e t a l f l u o r o s u l f a t e s , i n p a r t i c u l a r , t h o s e o f t h e 1 ^ a n d 1 1 ^ e l e m e n t s s h o w b a s i c b e h a v i o u r i n H S O g F , t h a t + 2 + - . i s , t h e d i s s o c i a t i o n t o f o r m M o r M a n d S 0 3 F i o n s o c c u r s ; t h e l a t t e r a r e b e s t d e t e c t e d b y e l e c t r i c a l c o n d u c t a n c e m e a s u r e m e n t s , s i n c e a s h i f t o f t h e s e l f i o n i z a t i o n e q u i l i b r i u m 1 2 2 f o r H S 0 3 F a c c o r d i n g t o e q u a t i o n C 3 . 1 0 ) o c c u r s . 2 H S 0 3 F ^ H 2 S 0 3 F + + S 0 3 F ~ ( 3 . 1 0 ) E l e c t r i c a l c o n d u c t a n c e m e a s u r e m e n t s w e r e m a d e a t 2 5 . 0 ° C o n s u s p e n s i o n s o f C ^ S O ^ F i n H S O g F . I n a t y p i c a l e x p e r i m e n t t h e c o n d u c t a n c e c e l l w a s a t t a c h e d t o t h e H S 0 3 F d o u b l e d i s t i l l a t i o n a p p a r a t u s a n d a b o u t 1 0 m l o f t h e a c i d w a s d i s t i l l e d i n t o i t . T h e c o n d u c t a n c e o f t h i s a c i d w a s m e a s u r e d a t 2 5 . 0 ° C . W e i g h e d a m o u n t s o f C ^ S O g F w e r e a d d e d t o t h i s a c i d a n d t h e m i x t u r e w a s s t i r r e d t h o r o u g h l y . E l e c t r i c a l c o n d u c t a n c e o f t h e s u s p e n s i o n s w e r e m e a s u r e d a f t e r t h e s y s t e m h a d e q u i l i b r a t e d . T a b l e ( 3 . 3 ) s u m m a r i z e s a t y p i c a l s e t o f d a t a o b t a i n e d d u r i n g t h e c o n d u c t a n c e m e a s u r e m e n t s . T h e c h a n g e i n e l e c t r i c a l c o n d u c t a n c e o b s e r v e d i s v e r y l o w a n d t h e s m a l l i n c r e a s e c a n b e a t t r i b u t e d t o c o n t a m i n a t i o n b y a t m o s p h e r i c m o i s t u r e d u r i n g t h e a d d i t i o n o f C ^ S O g F f r o m t h e w e i g h t b u r e t t e . T h i s c o n t a m i n a t i o n w o u l d h a v e r e s u l t e d i n t h e f o r m a t i o n o f s m a l l a m o u n t s o f H F a n d H ^ S O ^ , c o n t r i b u t i n g t o t h e s m a l l i n c r e a s e i n e l e c t r i c a l c o n d u c t a n c e . I t a p p e a r s t h a t a p p r e c i a b l e q u a n t i t i e s o f S O g F i o n s d o n o t d i s s o l v e i n t o s o l u t i o n w h e n C 7 9 S 0 „ F i s s u s p e n d e d i n H S O - F . I I I . C . . G R A P H I T E A C I D F L U O R O S U L F A T E S I I I . C . I S Y N T H E T I C R O U T E S T O A C I D F L U O R O S U L F A T E S O F G R A P H I T E S y n t h e s e s o f t h e a c i d f l u o r o s u l f a t e s C n S 0 3 F - m H S 0 3 F 1 2 3 T A B L E , 3 . . 3 ; E L E C T R I C A L C O N D U C T A N C E O F S U S P E N S I O N S O F C ? S 0 3 F i n H S 0 3 F C E L L C O N S T A N T = 8 . 1 0 c m 1 W e i g h t o f C „ S 0 „ F a d d e d C o n d u c t i v i t y S p e c i f i c C o n d u c t a n c e - 1 - 1 ( m g ) ( i ^ M h o ) ( n c m ) 0 . 0 1 6 . 5 3 1 . 3 3 9 x 1 0 4 6 3 . 0 1 6 . 7 4 1 . 3 5 6 X 1 0 4 1 1 5 . 3 1 6 . 8 0 1 . 3 6 1 x 1 0 4 1 6 0 . 1 1 6 . 9 0 1 . 3 6 8 x 1 0 4 2 1 5 . 2 1 9 . 5 7 1 . 5 8 5 x 1 0 4 3 0 5 . 3 2 1 . 5 7 1 . 7 4 8 x 1 0 4 1 2 4 w e r e a c h i e v e d p r i n c i p a l l y b y t w o m e t h o d s : ( a ) s u c c e s s i v e i n t e r c a l a t i o n o f S O g F a n d H S O g F a n d ( b ) s i m u l t a n e o u s i n t e r c a l a t i o n S O g F - a n d H S O g F . ( a ) S U C C E S S I V E I N T E R C A L A T I O N M E T H O D T h e f i r s t s t a g e b i n a r y f l u o r o s u l f a t e C y S O g F d i d n o t i n c o r p o r a t e a n y d e t e c t a b l e a m o u n t o f H S O ^ F i n t o t h e l a m e l l a r s p a c e s w h e n s u s p e n d e d i n H S O g F a t r o o m t e m p e r a t u r e f o r e x t e n d e d p e r i o d s o f r e a c t i o n t i m e . N e i t h e r m i c r o a n a l y s i s n o r N M R g a v e a n y i n d i c a t i o n o f i n t e r c a l a t e d a c i d . T h e r e f o r e , a f e a s i b l e m e t h o d t o i n c o r p o r a t e a c i d m o l e c u l e s s e e m e d t o b e s t a r t i n g w i t h a h i g h e r s t a g e b i n a r y f l u o r o s u l f a t e . S u c h a b i n a r y f l u o r o s u l f a t e o f s t a g e 2 c o m p o s i t i o n w a s p r e p a r e d b y t h e c o n t r o l l e d p r e s s u r e v a p o u r t r a n s p o r t m e t h o d . T h i s s a m p l e w a s e v e n t u a l l y r e a c t e d w i t h e x c e s s H S O g F a t r o o m t e m p e r a t u r e . ( b ) S I M U L T A N E O U S I N T E R C A L A T I O N M E T H O D T h e r e a c t i o n o f g r a p h i t e w i t h m i x t u r e s o f S^O^T^ a n d H S O ^ F w a s u s e d a s a n a l t e r n a t e m e t h o d t o s y n t h e s i z e a c i d f l u o r o s u l f a t e s w i t h a w i d e r c o m p o s i t i o n r a n g e . I n i t i a l a t t e m p t s u s i n g s u c h m i x t u r e s i n d i c a t e d p r e f e r e n t i a l i n t e r c a l a t i o n o f ^ 2 ^ 6 ^ 2 a s ° P P o s e d t o H S O ^ F . T h e c o m p o s i t i o n s o f t h e r e a g e n t m i x t u r e s a n d t h e r e s u l t i n g p r o d u c t s a r e d e s c r i b e d i n t h e f o l l o w i n g s e c t i o n s . 1 2 5 ' S Y N T H E S I S O F A . S T A G E 1 G R A P H I T E A C I D F L U P R O S U L F A T E • B Y S U C C E S S I V E I N T E R C A L A T I O N M E T H O D I n a t y p i c a l r e a c t i o n 0 . 3 0 1 0 g o f S P 1 g r a p h i t e p o w d e r w e r e e x p o s e d t o t h e S ^ O ^ F ^ v a p o u r f o r a b o u t a n h o u r a s u d e s c r i b e d i n s e c t i o n I I I B f o r t h e s y n t h e s i s o f s t a g e 2 b i n a r y g r a p h i t e f l u o r o s u l f a t e . T h e p r o d u c t o b t a i n e d w a s f o u n d t o b e p r e d o m i n a n t l y o f s t a g e 2 c o m p o s i t i o n a s w i t n e s s e d b y X - r a y d i f f r a c t i o n . M i c r o a n a l y s i s a n d g r a v i m e t r y i n d i c a t e d i t s c o m p o s i t i o n t o b e C ^ ^ S O ^ F . T h i s s a m p l e w a s r e a c t e d w i t h a n e x c e s s o f ( ^ 2 5 m l ) f r e s h l y d i s t i l l e d H S O g F f o r a b o u t 2 4 h o u r s a t r o o m t e m p e r a t u r e . A f t e r r e m o v i n g t h e e x c e s s H S O ^ F I n v a c u o t h e p r o d u c t w a s e x p o s e d t o a d y n a m i c v a c u u m t o y i e l d a f r e e f l o w i n g p o w d e r o f c o n s t a n t w e i g h t . T h e c o l o u r c h a n g e i n t h e p r o d u c t w a s n o t i c e a b l e : t h i s s a m p l e a p p e a r e d d a r k e r t h a n t h e s t a g e 2 b i n a r y f l u o r o s u l f a t e , C ^ ^ S O ^ F . T h e i n c r e a s e i n w e i g h t a g r e e d w i t h t h e r e s u l t s o f m i c r o a n a l y s i s t o s u g g e s t a c o m p o s i t i o n o f C . ^ S O g F - 1 . 0 5 H S O ^ F f o r t h i s m a t e r i a l ( A ) . M i c r o a n a l y s i s C H C a l c u l a t e d [ % ] 4 5 . 1 6 0 . 2 8 F o u n d [ % ] 4 4 . 8 1 0 . 2 3 X - r a y p o w d e r d i f f r a c t i o n o f t h i s c o m p o u n d s h o w e d l i n e s d u e t o ( 0 0 £ ) p l a n e s w i t h t h e m o s t i n t e n s e T i n e a s s i g n e d t o . ( 0 0 2 ) p l a n e s , c o n f i r m i n g t h e f i r s t s t a g e c o m p o s i t i o n . T h e o i n t e r l a y e r s e p a r a t i o n w a s c a l c u l a t e d t o b e 7 . 8 3 ± 0 . 0 3 A . 1 2 6 T h e . R a m a n s p e c t r u m o f t h i s c o m p o u n d d i d n o t r e v e a l a n y i n t e r -c a l a t e m o d e s , o n l y t h e E „ l a t t i c e m o d e w a s o b s e r v e d a t 2 g 2 1 6 4 0 c m I . T h e p o s i t i o n o f t h i s b a n d w a s i n a g r e e m e n t w i t h 6 8 6 9 t h e p r e v i o u s r e p o r t s ' o n f i r s t s t a g e a c c e p t o r G I C s . S i m i l a r r e a c t i o n s w e r e p e r f o r m e d w i t h H O P G , a n d s a m p l e s o f c o m p o s i t i o n C - ^ S O ^ F • m H S O g P w i t h m v a r y i n g f r o m 0 . 5 t o 1 . 2 , a c c o r d i n g t o t h e i n c r e a s e i n w e i g h t , w e r e p r e p a r e d . L o w e r H S O ^ F u p t a k e v a l u e s w e r e o b s e r v e d w h e n r e a c t i o n s w e r e c a r r i e d o u t w i t h l a r g e r p i e c e s w h i l e p o w d e r e d H O P G s e e m e d t o f o r m s a m p l e s w i t h h i g h e r a c i d c o n t e n t s . S Y N T H E S I S O F S T A G E 1 G R A P H I T E A C I D F L U O R O S U L F A T E S B Y S I M U L T A N E O U S I N T E R C A L A T I O N M E T H O D I n i t i a l a t t e m p t s o f t h e s i m u l t a n e o u s i n t e r c a l a t i o n o f S o 0 . F n w i t h H S 0 „ F h a d s h o w n t h a t S o 0 r F o o x i d a t i v e l y i n t e r c a l a t e d 2 6 2 3 2 6 2 a t a m u c h f a s t e r r a t e t h a n H S O ^ F a n d t h a t u n l e s s c o n t r o l l e d s m a l l a m o u n t s o f S^O^Y^ w e r e u s e d o n l y v e r y s m a l l a m o u n t s o f H S O g F w o u l d I n t e r c a l a t e . T h i s i s n o t e n t i r e l y s u r p r i s i n g i n v i e w o f t h e p r e v i o u s l y d i s c u s s e d g r e a t e r a b i l i t y o f b i s ( f l u o r o -s u l f u r y l ) p e r o x i d e t o u n d e r g o o x i d a t i v e i n t e r c a l a t i o n . T h e r e a c t i o n o f g r a p h i t e w i t h m i x t u r e s o f S ^ O g F ^ a n d H S O g F r e s u l t i n a c i d f l u o r o s u l f a t e s w i t h t h e a c i d m o l e c u l e s f a i r l y e v e n l y d i s t r i b u t e d i n a l l i n t e r c a l a t e l a y e r s . T h e c o m p o s i t i o n o f t h e i n t e r c a l a t i o n c o m p o u n d w a s d e t e r m i n e d b y t h e c o m p o s i t i o n o f t h e i n t e r c a l a n t m i x t u r e . T h e e x p e r i m e n t a l c o n d i t i o n s a n d t h e r e s u l t i n g p r o d u c t s a r e d e s c r i b e d i n t h i s s e c t i o n . 1 2 7 I n a t y p i c a l r e a c t i o n 0 . 1 9 . 5 9 g o f S P 1 g r a p h i t e p o w d e r w e r e a l l o w e d t o r e a c t w i t h a n e q u i m o l a r m i x t u r e o f H S O ^ F a n d ^ 2 ^ 6 ^ 2 ' k o t h p r e s e n t i n l a r g e e x c e s s f o r a p p r o x i m a t e l y 2 4 h o u r s . T h e e x c e s s r e a g e n t s w e r e r e m o v e d i n v a c u o a n d 0 . 4 3 0 2 g o f 1 9 1 o f a d a r k b l u e p o w d e r w e r e o b t a i n e d . F a n d H N M R o f t h i s s a m p l e i n d i c a t e d t h e p r e s e n c e o f b o t h S O ^ F a n d H S O ^ F a s i n t e r c a l a t e s . M i c r o a n a l y s i s i n d i c a t e d t h e p r e s e n c e o f H , b u t t h e v a l u e w a s c l o s e t o t h e d e t e c t i o n l i m i t ( 0 . 1 % ) . H e n c e a n a p p r o x i m a t e c o m p o s i t i o n o f C g 8 g S 0 3 F ( H ) ? i s s u g g e s t e d f o r t h i s s a m p l e ( B ^ ) b a s e d o n t h e p e r c e n t a g e o f c a r b o n d e t e r m i n e d b y m i c r o a n a l y s i s . M i c r o a n a l y s i s : F o u n d : ' % C = 4 6 . 0 0 % H « 0 . 1 . X - r a y p o w d e r d i f f r a c t i o n o n t h i s s a m p l e i n d i c a t e d t h e s t a g e o n e c o m p o s i t i o n w i t h . . l a y e r r e p e a t d i s t a n c e I o f 7 . 8 4 ± 0 . 0 3 A : S i m i l a r r e a c t i o n s w e r e c a r r i e d o u t u s i n g m i x t u r e s o f S o 0 _ F n a n d H S 0 „ F o f d i f f e r e n t m o l e r a t i o s . T h e s e m i x t u r e s 2 b 2 d c o n t a i n e d c o n t r o l l e d a m o u n t s o f S o 0 _ F o w i t h a n e x c e s s o f H S 0 „ F . 2 b 2 3 T a b l e ( 3 . 4 ) s u m m a r i z e s t h e e x p e r i m e n t a l d e t a i l s a n d t h e a n a l y t i c a l d a t a o f t h e a c i d f l u o r o s u l f a t e s s y n t h e s i z e d u s i n g m i x t u r e s o f S 2 0 g F 2 a n C * ^ S O ^ F . S a m p l e B ^ w a s p r e p a r e d u s i n g a m i x t u r e c o n t a i n i n g a n e x c e s s a m o u n t o f S 2 0 g F 2 t h a n t h a t r e q u i r e d t o f o r m C y ' S O ^ F a l o n g w i t h e q u a l n u m b e r o f m o l e s o f H S O ^ F . S a m p l e B 2 w a s p r e p a r e d u s i n g a s t o i c h i o m e t r i c q u a n t i t y o f S 2 0 g F 2 w i t h r e s p e c t t o t h e o x i d a t i o n o f t h e g r a p h i t e t o CrjSO^T w h i l e s a m p l e B 3 w a s p r e p a r e d w i t h a m i x t u r e c o n t a i n i n g o n l y s u f f i c i e n t a m o u n t o f S 2 O g F 2 t o c o n v e r t t h e g r a p h i t e t o C 2 ^ S 0 3 F . D u r i n g t h e s y n t h e s e s o f s a m p l e s B 2 a n d B 3 , f i r s t a n 128 T A B L E 3.4: R E A C T I O N S O F G R A P H I T E W I T H M I X T U R E S O F H S O g F A N D S 2 O g F 2 : E X P E R I M E N T A L D E T A I L S A N D A N A L Y T I C A L D A T A R e a c t i o n B . a m o u n t o f g r a p h i t e [ g ] a m o u n t o f g r a p h i t e [ m m o l e ] 0.1959 16.3 0.1357 11. 3 0.2905 24.21 a m o u n t o f S 2 ° 6 F 2 rg] a m o u n t o f S o 0 r F o [ m m o l e ] l 6 I a m o u n t o f H S 0 3 F [ g ] a m o u n t o f H S 0 3 F [ m m o l e ] ^8. 0 ^40 . 0 ^4 . 0 ^40 . 0 0 .1970 0 .997 -v5 . 0 ^50 . 0 0 .1135 0 . 573 ^5 . 0 o,50 . 0 w e i g h t o f p r o d u c t [ g ] 0.4302 0 . 3460 0.5860 m i c r o a n a l y s i s o f C [ % ] 46 . 00 40.11 49 . 04 m i c r o a n a l y s i s o f H [ % ] <0 .1 0 .22 0 . 33 s u g g e s t e d c o m p o s i t i o n C h a s e d o n a n a l y s i s ) C 6 . 8 9 S 0 3 F ( H ) ? C 5 . 6 S ° 3 F ( H ) 0 . 3 7 C 8 S ° 3 F ( H ) 0 . 6 1 2 9 e x c e s s 0 2 5 m l ) o f H S O ' ^ F w a s d i s t i l l e d i n t o t h e r e a c t o r c o n t a i n i n g g r a p h i t e a t - 1 9 8 ° C a n d w h i l e m a i n t a i n i n g t h e r e a c t o r a t t h i s t e m p e r a t u r e t h e r e q u i r e d a m o u n t o f S 2 0 g F 2 w a s d i s t i l l e d i n t o i t f r o m a c a l i b r a t e d p i p e t t e w h i c h w a s w e i g h e d b e f o r e a n d a f t e r t h e t r a n s f e r r i n g o f S o 0 r F o . T h e r e a c t i o n m i x t u r e w a s ° l b I t h e n a l l o w e d t o w a r m u p t o r o o m t e m p e r a t u r e , w h e n t h e r e a c t i o n c o m m e n c e d . I I I . D . R E S U L T S A N D D I S C U S S I O N I I I . D . l . B I N A R Y G R A P H I T E . F L U O R O S U L F A T E S C . S 0 o F n 3 T h e o x i d a t i v e i n t e r c a l a t i o n o f b i s ( f l u o r o s u l f u r y l ) p e r o x i d e , S ^ O ^ F ^ , I n t o g r a p h i t e r e p r e s e n t s a f a c i l e a n d v e r y c o n v e n i e n t r o u t e t o b i n a r y g r a p h i t e f l u o r o s u l f a t e s o f t h e t y p e C n S 0 3 F . A l i m i t i n g c o m p o s i t i o n o f C g g S O g F t o C ? 2 S ° 3 F i s r e a d i l y a c h i e v e d a n d b o t h g a s - a n d l i q u i d p h a s e i n t e r c a l a -t i o n i s f e a s i b l e o n a c c o u n t o f t h e r a t h e r c o n v e n i e n t p h y s i c a l p r o p e r t i e s ( s e e T a b l e 3 . 1 ) o f S 2 0 g F 2 . W h i l e P r o f e s s o r J . G . 8 0 H o o l e y o f t h i s d e p a r t m e n t h a s u n d e r t a k e n , i n a p a r a l l e l s t u d y , t o i n v e s t i g a t e t h e g a s p h a s e i n t e r c a l a t i o n f o r v a r i o u s t y p e s o f g r a p h i t e f o c u s s i n g a t t e n t i o n o n f a c t o r s l i k e s a m p l e s i z e , d e g r e e o f o r d e r i n t h e g r a p h i t e s a m p l e c h o s e n a n d t h e t h r e s h o l d p r e s s u r e , o u r i n t e r e s t w a s d i r e c t e d t o w a r d s t h e l i q u i d p h a s e i n t e r c a l a t i o n , u s i n g o n l y a l i m i t e d n u m b e r o f t y p e s , o f g r a p h i t e ( S P 1 a n d t o a l e s s e r d e g r e e H O P G ) t o p r o d u c e s t a g e 1 G I C s . 130 The l i m i t i n g c o m p o s i t i o n o f 'vC^SO F found by us agrees 3 8 0 w e l l w i t h P r o f e s s o r Hooley's f i n d i n g s and a more r e c e n t g f o r m u l a t i o n by B a r t l e t t e t a l . , who had f i r s t s t u d i e d t h i s r e a c t i o n t y p e and had proposed an i o n i c f o r m u l a t i o n C^SO^F . Such a f o r m u l a t i o n would suggest a r a t h e r h i g h charge d e n s i t y o f one u n i t p o s i t i v e charge p e r seven carbon atoms s h o u l d the i o n i c f o r m u l a t i o n prove t o be c o r r e c t . A t t h e s t a r t o f t h i s s t u d y t h i s r a t h e r h i g h charge d e n s i t y on g r a p h i t e caused l i t t l e c o n cern f o r two r e a s o n s : ( i ) R a d i c a l d i s s o c i a t i o n o f S 2 0 g F 2 a c c o r d i n g t o : S o 0 c F o ^ 2S0„F' (3.2) Z 0 Z o and subsequent r e d u c t i o n t o t h e f l u o r o s u l p h a t e i o n a c c o r d i n g t o e q u a t i o n (3.11) 2S0 3F + 2e • 2S0 3F (3.11) was w e l l e s t a b l i s h e d and had t o be viewed as the most p l a u s i b l e course o f r e a c t i o n ; and ( i i ) o x i d a t i v e i n t e r c a l a t i o n o f s t r o n g l y o x i d i z i n g m e t a l hexa-f l u o r l d e s such as O s F ^ 8 * 3 , o r o f s a l t s l i k e 0*AsF_ ^ 6 2 b 2 8b o r t h e use o f e l e m e n t a l f l u o r i n e i t s e l f , e x e m p l i f i e d by the o v e r a l l r e a c t i o n ( 3 . 1 2 ) . SC + A s F c + - F „ > .CQASFc (3.12) b 2 2 o b 1 3 1 had r e p o r t e d l y r e s u l t e d i n g r a p h i t e s a l t s o f t h e g e n e r a l type C„MF r . C o n s i d e r i n g t h e s m a l l d i f f e r e n c e i n t h e i n t e r c a l a t e o b i o n s i z e a f o r m u l a t i o n as C^SOgF i s not unexpected. I n i t i a t e d by t h e u n u s u a l l y low e l e c t r i c a l c o n d u c t i v i t y v a l u e s observed f o r some o f t h e s e m a t e r i a l s such as CgAsFg i n c r e a s i n g doubt has been c a s t on the s i m p l e i o n i c 1 1 2 ( c i ) model and over t h e l a s t two y e a r s e v i d e n c e from ESCA, 1 9 r e f l e c t i v i t y and F NMR s t u d i e s had suggested t h e p r e s ence of d i s c r e t e c o v a l e n t C-F bonds a c t i n g as c a r r i e r s c a t t e r i n g c e n t r e s , t h u s d e g r a d i n g t h e m e t a l l i c b e h a v i o u r o f t h i s m a t e r i a l . ' An i o n i c s a l t l i m i t a t ^ C^q has r e c e n t l y been suggested and the c l a i m i s made t h a t such a l i m i t has g e n e r a l a p p l i c a b i l i t y . S i m i l a r i t y i n t h e g r a p h i t e b i s u l f a t e system, where a n o d i c o x i d a t i o n produces f i r s t s t age m a t e r i a l s o f the c o m p o s i t i o n C2 +^HS0 4 • 2.51^230^ w h i l e " o v e r c h a r g i n g " o r " o v e r o x i d a t i o n " may f o r m a l l y l e a d t o C-^ s p e c i e s , the p r e s e n c e of d i s c r e t e c o v a l e n t C-0 bonds i s p o s t u l a t e d " ^ 2 ^ ^ t o be a c t i n g a g a i n i n a d e g r a d i n g manner on m e t a l l i c c o n d u c t i o n . S i n c e HSO^ and SO^F are i s o e l e c t r o n i c , t h e s e c o n c l u s i o n s are p e r t i n e n t and need d e t a i l e d c o n s i d e r a t i o n . In summary i t seemed, from t h e e v i d e n c e p r e s e n t e d , t h a t a g e n e r a l " i o n i c model" e x i s t s , as suggested by F i s c h e r e t . a l : . t o be ^ C2+^ beyond which p o i n t c o v a l e n t C-F or C-0 bond f o r m a t i o n o c c u r s . T h e r e f o r e i t became n e c e s s a r y t o r e - e v a l u a t e a l l e v i d e n c e f o r g r a p h i t e f l u o r o s u l f a t e C^SOgF , a t a p o i n t i n t h i s s tudy when the major p a r t o f the r e s e a r c h had been 1 3 2 c o m p l e t e d . T h i s r e - e v a l u a t i o n , u n d e r t a k e n h e r e , w i l l b e c a r r i e d o u t i n t h r e e d i s t i n c t s t e p s w i t h t h e i n t e n t i o n s t o : ( a ) e s t a b l i s h b e y o n d d o u b t t h e c h e m i c a l c o m p o s i t i o n o f C y S O ^ F a n d d i s c u s s i t s c h e m i c a l i d e n t i t y b y d i s c u s s i n g a n d h o p e f u l l y e l i m i n a t i n g i m p r o b a b l e m o d e l s ; ( b ) s u r v e y a l l s t r u c t u r a l i n f o r m a t i o n a n d p r e s e n t a c o n s i s t e n t s t r u c t u r e o r p a c k i n g m o d e l ; a n d ( c ) p r e s e n t a r e a l i s t i c a l t e r n a t e m o d e l t o t h e , i n o u r o p i n i o n , r a t h e r a r b i t r a r y i o n i c s a l t l i m i t s p r o p o s e d w i t h e i t h e r i o n i c b o n d i n g o r d i s c r e t e c o v a l e n t b o n d f o r m a t i o n p o s s i b l e . I t a p p e a r s t h a t t h e c o m p o s i t i o n o f C y S O ^ F h a d b e e n d e d u c e d o n l y b y g r a v i m e t r y i n t h e p a s t . S i n c e b i s ( f l u o r o -s u l f u r y l ) p e r o x i d e , ^2Q6^2'' m a ^ a c i : a s o x ^ d e o r f l u o r i d e f o r m i n g r e a g e n t , g r a v i m e t r y m a y b e v i e w e d a s i n s u f f i c i e n t a n d a c o m p l e t e a n a l y s i s n e e d e d , i n c l u s i v e o f a d i r e c t d e t e r m i n a t i o n o f o x y g e n . T h e o x y g e n c o n t e n t o f t h e s a m p l e w a s d e t e r m i n e d b y M r . P . B o r d a o f t h i s d e p a r t m e n t b y a d o p t i n g a p y r o l y s i s m e t h o d . T h i s m e t h o d i n v o l v e s p y r o l y s i s o f t h e s a m p l e i n a H e o a t m o s p h e r e a t 1 0 8 0 C i n a c o l u m n c o n t a i n i n g M 0 C 2 a n d C , w h e r e t h e o x i d e s p r o d u c e d a r e c o n v e r t e d t o C O , t h e a m o u n t o f w h i c h i s m e a s u r e d b y a d e t e c t o r . A s a m p l e o f c o m p o s i t i o n C g g S O ^ F b y g r a v i m e t r y g a v e t h e f o l l o w i n g r e s u l t s o n m i c r o a n a l y s i s : C S F 0 H T O T A L C a l c . f o r C c „ c S 0 o F ( % ) 4 5 . 0 0 1 7 . 7 8 1 0 . 5 5 2 6 . 6 7 - 1 0 0 . 0 0 b . / b 0 F o u n d ( % ) 4 4 . 4 0 1 7 . 5 5 1 0 . 4 8 2 7 . 0 5 0 . 0 0 9 9 . 4 8 1 3 3 N o H N M R r e s o n a n c e w a s - d e t e c t e d . M a s s b a l a n c e : 9 9 . 4 8 % - s u f f i c i e n t l y c l o s e t o t h e e x p e c t e d 1 0 0 % c o n s i d e r i n g t h a t c a r b o n c o n t e n t v a l u e s f o r f l u o r i n e c o n t a i n i n g G I C s a r e n o t o r i o u s l y o n t h e l o w s i d e o f t h e e x p e c t e d v a l u e s . A t o m i c r a t i o s ( o b s e r v e d ) : S : 0 : F = 1 : 3 . 0 8 2 : 1 . 0 0 6 a n d o v e r a l l c o m p o s i t i o n : C g ^ S O ^ F . T h e s e r e s u l t s r u l e o u t t h e f o l l o w i n g p o s s i b i l i t i e s a n d e x p l a n a t i o n s : C i ) T h e p r e s e n c e o f a n y d e t e c t a b l e a m o u n t o f H S O ^ F a s c o -i n t e r c a l a t e a n d i n t e r p r e t a t i o n o f g r a p h i t e f l u o r o -s u l f a t e a s a n a c i d s a l t . S i n c e S 2 0 g F 2 i n o u r l a b o r a t o r y i s p r o d u c e d i n a c a t a l y t i c g a s p h a s e r e a c t i o n o f S O g a n d T ^ a - t ^ 1 8 0 ° C a t m o s p h e r i c m o i s t u r e c o u l d h a v e b e e n t h e o n l y p o s s i b l e s o u r c e o f H S O ^ F a c c o r d i n g t o e q u a t i o n ( 3 . 1 3 ) . H o 0 + S o 0 . F o 5 = ^ 2 H S 0 o F + - 0 o ( 3 . 1 3 ) I l b I 3 2 2 ( i i ) T h e f o r m a t i o n o f c o v a l e n t C - F g r o u p s , p e r h a p s i n a s i d e r e a c t i o n . I n a d d i t i o n t o t h e a n a l y s i s , i t s h o u l d b e m e n t i o n e d t h a t i n t e r c a l a t i o n a n d d e - i n t e r c a l a t i o n s t u d i e s a t e l e v a t e d t e m p e r a t u r e d i d n o t p r o v i d e a n y e v i d e n c e f o r S O ^ e v o l u t i o n , a s e x p e c t e d a c c o r d i n g t o e q u a t i o n ( 3 . 1 4 ) . C S 0 o F • C F + S 0 o ( 3 . 1 4 ) n 3 n 3 1 3 4 ( i i i ) T h e f o r m a t i o n o f g r a p h i t e o x i d e a s a s i z e a b l e i m p u r i t y , f o r m e d p o s s i b l y i n a s i d e r e a c t i o n a c c o r d i n g t o t h e g e n e r a l e q u a t i o n : 2 C S 0 o F — - * C 0 0 + S o 0 c F o ( 3 . 1 5 ) n 3 An l b l A g a i n t h e r e i s n o e v i d e n c e f o r t h e f o r m a t i o n o f b i s -( s u l f u r y l ) o x i d e , ^rph^l* d u r i n g i n t e r c a l a t i o n o r 1 9 d e - i n t e r c a l a t i o n , e v e n t h o u g h F N M R s h o u l d a l l o w i t s 1 1 8 d e t e c t i o n i n b u l k S 2 0 g F 2 ( < 5 = 4 0 . 4 p p m ) o n a c c o u n t 1 1 8 o f i t s c h e m i c a l s h i f t o f 4 8 . 8 p p m r e l a t i v e t o C F C l ^ A l l t h e s e p o i n t . ' . t o a n o v e r a l l i n t e r c a l a t e c o m p o s i t i o n c l o s e t o S O ^ F , a n d t h e a b s e n c e o f a p p r e c i a b l e a m o u n t s o f e i t h e r H S O g F o r o f g r a p h i t e f l u o r i d e o r g r a p h i t e o x i d e . S T R U C T U R A L F E A T U R E S O F B I N A R Y G R A P H I T E F L U O R O S U L F A T E ( i ) I n t e r l a y e r s e p a r a t i o n : I n t e r l a y e r s e p a r a t i o n o f s t a g e 1 g r a p h i t e f l u o r o s u l f a t e C y S O ^ F i s f o u n d i n t h i s o s t u d y t o b e 7 . 8 1 ± 0 . 0 3 A c o m p a r e d t o t h e r e p o r t e d ° ? R h ° 8 v a l u e s o f 7 . 8 6 ± " 0 . 0 3 A a n d 7 . 7 3 A f o r b i n a r y g r a p h i t e f l u o r o s u l f a t e s . T h e a c i d f l u o r o s u l f a t e s 4 9 8 C 5 + 1 H S 0 3 F a n d C y H ^ S O g F s h o w i n t e r l a y e r s e p a r a t i o n s o o o f 8 . 0 5 A a n d 7 . 8 1 A r e s p e c t i v e l y . ( i i ) R a m a n s p e c t r a : T h e R a m a n b a c k s c a t t e r i n g s p e c t r a o n C y S O g F s h o w f o u r , r e l a t i v e l y b r o a d p e a k s a t 1 6 3 5 1 3 5 ( E 0 n m o d e ) , 1 1 2 3 , 8 3 0 a n d 6 0 4 c m -1 1 9 ( i i i ) F N M R : A s i n g l e s h a r p l i n e a t 1 2 - 1 4 p p m r e l a t i v e t o C F C l g i s o b s e r v e d f o r s a m p l e s o f c o m p o s i t i o n s C g rj_rj ^ ^ O ^ F . A s F i g . ( 3 . 1 ) i l l u s t r a t e s s u r f a c e a d s o r b e d S^O^F^ s h o w s i t s r e s o n a n c e a t ^ 4 0 p p m i n g o o d a g r e e m e n t w i t h t h e h i g h r e s o l u t i o n 6 v a l u e f o r l i q u i d ^ 2 ^ 6 ^ 2 ' T h i s b r o a d f e a t u r e d i s a p p e a r s o n p u m p i n g a n d i s n o t f o u n d f o r v a c u u m s t a b l e C y S O ^ F . H i g h e r s t a g e b i n a r y g r a p h i t e f l u o r o s u l f a t e s s h o w s i m i l a r s i n g l e l i n e s p e c t r a a n d h a v e r a t h e r s i m i l a r 6 v a l u e s . ( i v ) E S R s p e c t r a : P o w d e r s p e c t r a a t r o o m t e m p e r a t u r e g i v e a g - v a l u e o f 2 . 0 0 2 4 , c l o s e t o t h e f r e e e l e c t r o n v a l u e . F i r s t d e r i v a t i v e l i n e s f o r C y S O ^ F a r e t y p i c a l l y a s y m m e t r i c a n d a g r e e w e l l w i t h s p e c t r a o b t a i n e d f o r C ^ S O g C F g b y u s ( g = 2 . 0 0 3 0 ) w h i c h i s d i s c u s s e d i n t h e f o l l o w i n g c h a p t e r . ( v ) E l e c t r i c a l c o n d u c t i v i t i e s : T h e e l e c t r i c a l c o n d u c t i v i t y ( a ) o f C y 2 S 0 g F p r e p a r e d f r o m H O P G w a s f o u n d t o b e 4 . 8 x 1 0 4 o h m " 1 c m " 1 ( a / a = 2 . 1 ) . D e t a i l s o f t h e c o n d u c t i v i t y m e a s u r e m e n t s a r e d i s c u s s e d i n C h a p t e r V I I . T h e a b o v e m e n t i o n e d s t r u c t u r a l f e a t u r e s a n d p h y s i c a l p r o p e r t i e s s u g g e s t t h a t C y S O ^ F i s a s t a g e 1 i n t e r c a l a t i o n c o m p o u n d w i t h t h e i n t e r c a l a t e o f t h e c h e m i c a l c o m p o s i t i o n S O g F a c t i n g a s a n e l e c t r o n a c c e p t o r . T h e f l u o r o s u l f a t e i o n , S O g F " 1 3 6 i s t h e o b v i o u s c h o i c e , h o w e v e r t h e f o r m u l a t i o n a s C ^ S O ^ F i m p l i e s a n u n p r e c e d e n t l y h i g h i o n i c s a l t l i m i t , s o t h a t t h e p o s s i b l e p r e s e n c e o f n e u t r a l f l u o r o s u l f a t e s p e c i e s a s c o - i n t e r -1 9 c a l a t e m u s t b e c o n s i d e r e d . T h e F N M R s p e c t r u m , a s i n g l e p e a k a t ^ 1 2 p p m , h e n c e s t r o n g l y u p f i e l d f r o m t h e u s u a l r a n g e 1 9 1 1 8 o f F r e s o n a n c e s a t ^ 3 5 t o 4 5 p p m r e l a t i v e t o C F C l ^ d o e s n o t p r o v i d e d i r e c t e v i d e n c e f o r s u c h s p e c i e s . A n e l e c t r o n t r a n s f e r e q u i l i b r i u m o f t h e t y p e : S 0 3 F " + e - : ^ = i S 0 3 F ( 3 . 1 6 ) i s n o t s u p p o r t e d b y t h e E S R s p e c t r u m . T h e E S R s p e c t r u m o f 1 1 3 t h e S O ^ F r a d i c a l i s w e l l k n o w n a n d e x p e c t e d t o b e q u i t e d i f f e r e n t f r o m t h e o b s e r v e d D y s o n i a n l i n e , t y p i c a l f o r m e t a l l i c c o n d u c t o r s . T h e e q u i l i b r i u m : S o 0 c F o + 2 e = ^ 2 S 0 o F ( 3 . 1 7 ) 2 6 2 3 i s m o s t s u i t a b l e t o d e s c r i b e b o t h o x i d a t i v e i n t e r c a l a t i o n a n d r e d u c t i v e d e i n t e r c a l a t i o n , i n v o l v i n g i n b o t h i n s t a n c e s t h e S 0 _ F * r a d i c a l a s i n t e r m e d i a t e . T h e r e i s h o w e v e r n o e v i d e n c e f o r t h e p r e s e n c e o f S _ 0 » F „ i n r e a s o n a b l e c o n c e n t r a t i o n i n t h e 2 6 2 i n t e r l a m e l l a r s p a c e o f C ^ S O ^ F . I t s m o l e c u l a r s t r u c t u r e , a s t a g g e r e d c o n f o r m a t i o n o f p o i n t g r o u p C 2 a c c o r d i n g t o t h e p o l a r i z e d R a m a n s p e c t r u m , w o u l d h a v e t o b e " a l t e r e d " o n 1 9 i n t e r c a l a t i o n a n d a s e c o n d F N M R r e s o n a n c e o r a t l e a s t e x c h a n g e b r o a d e n i n g o f t h e o b s e r v e d s i n g l e r e s o n a n c e w o u l d b e e x p e c t e d a s w e l l a s . s o m e E S R e v i d e n c e f o r r a d i c a l i n t e r m e d i a t e s 1 3 7 A s e c o n d F N M R r e s o n a n c e w o u l d a l s o b e e x p e c t e d f o r f l u o r o s u l f a t e g r o u p s c o v a l e n t l y b o n d e d t o g r a p h i t e l a y e r s . I t s h o u l d b e k e p t i n m i n d t h a t a n i o n i c s a l t l i m i t o f ^ ' C g O a s p o s t u l a t e d b y F i s c h e r w o u l d i m p l y a b o u t t w o t h i r d s o f a l l S O ^ F g r o u p s t o b e c o v a l e n t l y b o n d e d . T h e p r e s e n c e o f S O ^ F a s t h e s o l e i n t e r c a l a t e s p e c i e s , i s m o s t c o n s i s t e n t w i t h b o t h t h e e x p e r i m e n t a l i n t e r l a y e r . . . . . 1 1 4 s e p a r a t i o n a n d t h e l i m i t i n g c o m p o s i t i o n . T h e r e p o r t e d c r y s t a l s t r u c t u r e o f K S O g F s u g g e s t s a n i o n i c r a d i u s o f a b o u t o _ 2 . 2 5 A f o r S O ^ F , i n c l o s e a n a l o g y t o K a p u s t i n s k i i ' s t h e r m o -c h e m i c a l r a d i i 1 1 5 o f C l O ^ " ( 2 . 3 6 A ) a n d S o J ~ ( 2 . 3 0 A ) . T h e o - o r e s u l t i n g e f f e c t i v e d i a m e t e r o f 4 . 5 A f o r S O ^ F a n d t h e 3 . 3 5 A f o r t h e t h i c k n e s s o f c a r b o n l a y e r s s u g g e s t a n i n t e r l a y e r o s e p a r a t i o n o f 7 . 8 5 A i n r e a s o n a b l e a g r e e m e n t w i t h t h e e x p e r i -o m e n t a l v a l u e o f 7 . 8 1 A , w i t h C o u l o m b i c i n t e r a c t i o n c a u s i n g c o n t r a c t i o n . T h e s a m e c r y s t a l s t r u c t u r e o f K S O g F r e p o r t s , a u n i t c e l l ° 3 v o l u m e o f 3 7 0 . 0 A w i t h 4 K S O g F f o r m u l a u n i t s p e r u n i t c e l l o g w h i c h s u g g e s t s a f o r m u l a v o l u m e o f 9 2 . 5 A o r a n a p p r o x i m a t e . : ° 3 a n i o n v o l u m e o f 7 4 A ( s e e A p p e n d i x O n t h e o t h e r h a n d o o t h e e x p e r i m e n t a l l a y e r s e p a r a t i o n o f 7 . 8 1 A , a l l o w i n g 3 . 3 5 A f o r t h e t h i c k n e s s o f t h e c a r b o n l a y e r s u g g e s t a n a v a i l a b l e o s p a c e o f ^ 1 1 . 7 A p e r c a r b o n a t o m . T h i s w o u l d s u g g e s t a l i m i t -i n g c o m p o s i t i o n o f C g ^ S O ^ F f o r t h e c l o s e a n i o n p a c k i n g , a g a i n i n e x c e l l e n t a g r e e m e n t w i t h t h e e x p e r i m e n t a l f i n d i n g s . C l o s e a n i o n p a c k i n g , a p p r o x i m a t e l y t h e m o l e c u l a r S O ^ F a n i o n b y a t e t r a h e d r o n , m a y b e a c h i e v e d b y t w o p r i n c i p a l 1 3 8 p a c k i n g m o d e s a s s h o w n i n F i g . ( 3 . 3 ) : ( a ) T h e 3 - 1 m o d e w h e r e 3 a p e x a t o m s a r e i n c o n t a c t w i t h o n e c a r b o n l a y e r a n d t h e f o u r t h a t o m i s i n c o n t a c t w i t h t h e o t h e r c a r b o n l a y e r , a n d ( b ) t h e 2 - 2 m o d e w h e r e 2 a p e x a t o m s a r e i n c o n t a c t w i t h e a c h o f t h e a d j a c e n t c a r b o n l a y e r s . P o s i t i o n a l a l t e r n a t i o n w i t h i n t h e i n t e r c a l a t e l a y e r m a y r e s u l t g i n t i g h t a n i o n p a c k i n g a s d e s c r i b e d b y B a r t l e t t a n d M c Q u i l l a n . W h i l e b o t h p a c k i n g m o d e s a r e c o n s i s t e n t w i t h t h e p r i n c i p l e o f c l o s e p a c k i n g a s w e l l a s t h e o b s e r v e d i n t e r l a y e r s e p a r a t i o n , i t i s i m p o r t a n t t o r e a l i z e t h a t a l l a p i c a l a t o m s . . a r e i n d i r e c t c o n t a c t w i t h t h e c a r b o n ' p l a n e s i n e a c h i n s t a n c e , w h i c h o p e n s u p t h e d i s t i n c t p o s s i b i l i t y o f c o v a l e n t a n i o n - c a t i o n i n t e i i a c t i o n . T h e c h e m i s t r y o f m e t a l f l u o r o s u l f a t e s p r o v i d e s m a n y e x a m p l e s o f a n i o n c o o r d i n a t i o n , p r e f e r e n t i a l l y i n v o l v i n g t h e m o r e " b a s i c " o x y g e n a t o m s a s e l e c t r o n d o n o r s a n d m e t a l i o n s a s e l e c t r o n a c c e p t o r s . I n p a r t i c u l a r , a n i o n c o o r d i n a t i o n w i t h t h e S 0 „ F g r o u p a c t i n g a s a t r i d e n t a t e l i g a n d o f f e r s a d i s t i n c t p a r a l l e l . T h i s c o o r d i n a t i o n t y p e i s o f t e n f o u n d f o r f l u o r o -s u l f a t e s o f t h e t y p e M ( S 0 g F ) 2 a n d t h e . r e s u l t i n g r e g u l a r o c t a h e d r o n c o o r d i n a t i o n i s s h o w n i n F i g . ( 3 . 4 ) . T h e S O g F g r o u p s r e t a i n C g v s y m m e t r y a n d a r e c e n t l y p u b l i s h e d R a m a n s t u d y " ' " "'"^^^ o f t h e g r o u p l i b f l u o r o s u l f a t e s o f f e r s a g o o d c o m p a r i s o n : t h e t h r e e " i n t e r c a l a t e " b a n d s 1 3 9 F I G . 3 . 3 P O S S I B L E O R I E N T A T I O N S O F S 0 3 F " I O N S I N T H E I N T E R C A L A T E L A Y E R S .: ( A ) T H E 3 - 1 M O D E ( B ) T H E 2 - 2 M O D E 1 4 0 F I G . 3 . 4 P R O P O S E D S T R U C T U R E O F M ( S 0 3 F ) 2 ( F R O M R E F E R E N C E 1 1 6 ) 1 4 1 o b s e r v e d i n t h e b a c k s c a t t e r i n g R a m a n s p e c t r u m a t 1 1 2 3 , 8 3 0 a n d 6 0 4 c m a r e i n p o s i t i o n s , e x p e c t e d f o r t h e t h r e e m o s t i n t e n s e R a m a n b a n d s o f a ^ - s y m m e t r y . T h e r e m a i n i n g t h r e e e - m o d e s a r e o f r a t h e r l o w i n t e n s i t y a n d i t i s n o t s u r p r i s i n g , t h a t t h e s e b a n d s a r e n o t o b s e r v e d i n t h e R a m a n s p e c t r u m o f C ^ S O ^ F . S i g n i f i c a n t d i f f e r e n c e s i n b o t h b a n d p o s i t i o n a n d r e l a t i v e b a n d i n t e n s i t i e s a r e o b s e r v e d f o r i o n i c S O ^ F i n t h e i r R a m a n s p e c t r a [ s e e f o r e . g . C a n . J . C h e m . , ' 4 _ 9 , 3 5 ( 1 9 7 1 ) ] e v e n t h o u g h h e r e C ^ ^ s y m m e t r y i s f o u n d . T h e c o v a l e n t a n i o n - c a t i o n i n t e r a c t i o n p r o p o s e d f o r g r a p h i t e f l u o r o s u l f a t e m a y b e s e e n a s a c h a r g e c o m p e n s a t i n g b a c k d o n a t i o n p r o c e s s , c a p a b l e o f r e d u c i n g t h e o v e r a l l p o s i t i v e c h a r g e d e n s i t y i n t h e g r a p h i t e p l a n e , a s i m p l i e d b y t h e f o r m u l a t i o n a s C ^ S O g F . T h e m o d e l c o u l d a l s o i m p l y d i r e c t c o n t a c t b e t w e e n f l u o r i n e a n d t h e g r a p h i t e p l a n e s r e s u l t i n g i n m o r e e f f e c t i v e s c r e e n i n g f o r t h e F n u c l e u s , a s i s a p p a r e n t f r o m t h e o b s e r v e d c h e m i c a l s h i f t . A d d i t i o n a l o b s e r v a t i o n s m a y n o w b e e a s i l y r a t i o n a l i z e d . U n l i k e i o n i c f l u o r o s u l f a t e s s u c h a s K S O ^ F b u t v e r y m u c h l i k e t h e p o l y m e r i c l i b f l u o r o s u l f a t e s , C y S O g F d o e s n o t a c t a s a b a s e i n H S O g F ( s e e s e c t i o n I I I . B . 3 ) , b u t r a t h e r l i k e a n i n s o l u b l e n o n e l e c t r o l y t e . T h e c o v a l e n t i n t e r a c t i o n , b e t w e e n g r a p h i t e a n d f l u o r o -s u l f a t e i s e x p e c t e d t o h a v e a d i s t o r t i n g e f f e c t o n t h e g r a p h i t e p l a n e s and h e n c e a r e d u c i n g e f f e c t o n t h e b a s a l p l a n e conducT-t i v i t y . I t f o l l o w s t h a t i n h i g h e r s t a g e g r a p h i t e f l u o r o -1 4 2 s u l f a t e s , t h e c o v a l e n t i n t e r a c t i o n d e c r e a s e s w h i l e b a s a l p l a n e c o n d u c t i v i t i e s i n c r e a s e , i n a g r e e m e n t w i t h e x p e r i m e n t a l r e s u l t s . g I n t e r e s t i n g l y , B a r t l e t t a n d M c Q u i l l a n h a d c o m m e n t e d o n a " n o t i c e a b l e l a c k o f c r y s t a l l i n i t y f o r C ^ S O ^ F " w h i c h c o u l d " s i g n i f y a d i s t o r t i o n o f t h e c a r b o n l a y e r s " . T h e p r o p o s e d a n i o n - c a t i o n i n t e r a c t i o n p r o v i d e s a c a u s e f o r s u c h d i s t o r t i o n . T h e m o d e l d e v e l o p e d h e r e f o r C y S O g F m a y w e l l b e e x t e n d e d t o o t h e r g r a p h i t e s a l t s . T h e c o n c e p t o f i n t e r a c t i n g , c o o r d i n a -t e d i o n s i s n o t n o v e l a n d c e r t a i n l y l e s s a r t i f i c i a l a n d r e s t r i c t i v e t h a n p o s t u l a t i n g i o n i c s a l t l i m i t s . T h e t i g h t l y b o n d e d s t r u c t u r e s u g g e s t e d h e r e i s n o t i n c o n f l i c t w i t h a n y c h e m i c a l f e a t u r e s t o b e d i s c u s s e d s u b s e q u e n t -l y . F o r e . g . s o l v o l y s i s o f f l u o r o s u l f a t e s i n H S O g C F g r e s u l t i n g i n a q u a n t i t a t i v e S O ^ F / H S O g C F ^ e x c h a n g e h a s r e c e n t l y b e e n a p p l i e d ' t o t h e s y n t h e s i s o f H g C S O g C F ^ f r o m H g ( S 0 3 F ) 2 < I I I . D . 2 . G R A P H I T E A C I D . F L U O R O S U L F A T E S C S O 0 . F . m H S . 0 o F n 3 3 _ W h e n a t t e m p t i n g t o c o n n e c t t h e b i n a r y g r a p h i t e f l u o r o s u l f a t e s w i t h C y S O g F a s t h e f i r s t s t a g e c o m p o s i t i o n a n d t h e a c i d f l u o r o s u l f a t e s l i k e f o r e . g . t h e f i r s t s t a g e c o m p o u n d C 2 4 S 0 3 F ~ ' m H S 0 3 F ^ w h e r e m = 2 - 2 . 5 ) , o n e s h o u l d f i r s t e s t a b l i s h t h e d i s t i n g u i s h i n g f e a t u r e s b e t w e e n b o t h g r o u p s . T h e m o s t p r o m i n e n t f e a t u r e i n t h i s s e n s e , i m p l i e d b y t h e c o m p o s i t i o n s a l o n e i s t h e e x t e n t o f o x i d a t i o n o f t h e c a r b o n p l a n e s . T h e b i n a r y g r a p h i t e f l u o r o s u l f a t e s c o r r e s p o n d t o a g r e a t e r 1 4 3 o x i d a t i o n o f c a r b o n p l a n e s t h a n t h e a c i d f l u o r o s u l f a t e s o f t h e s a m e s t a g e . T h e f i r s t s t a g e b i n a r y f l u o r o s u l f a t e w i t h a u n i t p o s i t i v e c h a r g e p e r a p p r o x i m a t e l y 7 c a r b o n a t o m s n a t u r a l l y i n v o l v e s a h i g h e r c h a r g e t h a n t h e f i r s t s t a g e a c i d f l u o r o -s u l f a t e . A l t h o u g h d i r e c t m e a s u r e m e n t s o f t h e e x t e n t o f c h a r g e t r a n s f e r w e r e n o t c a r r i e d o u t i n t h i s w o r k , f r o m t h e f i r s t s t a g e c o m p o s i t i o n s o f b o t h t y p e s o f f l u o r o s u l f a t e s o n e c a n e x p e c t t h e b i n a r y f l u o r o s u l f a t e s t o h a v e a c h a r g e t r a n s f e r f a c t o r , f . " , 3 t o 3 . 5 t i m e s h i g h e r t h a n t h e a c i d f l u o r o s u l f a t e s . A g a i n , t h e r e a r e s e v e r a l p h y s i c a l a s p e c t s w h e r e t h e d e g r e e o f c h a r g e t r a n s f e r i s e x p e c t e d t o r e f l e c t i n d e t e c t a b l e v a r i a t i o n s . O n e s u c h p r o p e r t y i s t h e s e p a r a t i o n o f t w o c a r b o n l a y e r s w i t h a n i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m ( I ) . T h e J s o b v i o u s d i f f e r e n c e i n t h e i n t e r c a l a t e l a y e r o f a c i d f l u o r o -s u l f a t e s a n d b i n a r y f l u o r o s u l f a t e s i s t h a t t h e C o u l o m b r e p u l s i o n b e t w e e n t h e a n i o n s m i g h t b e d e c r e a s e d b y t h e p r e s e n c e o f n e u t r a l a c i d m o l e c u l e s i n t h e f o r m e r w h e r e a s i t m i g h t c a u s e " t i p p i n g " o f s o m e o f t h e a n i o n s o u t o f t h e l a y e r i n t h e b i n a r y f l u o r o s u l f a t e . I f t h i s i s t h e d o m i n a n t f e a t u r e i n t h e s e s y s t e m s o n e w o u l d e x p e c t h i g h e r v a l u e s f o r t h e s a n d w i c h t h i c k n e s s , I , o f b i n a r y f l u o r o s u l f a t e s t h a n t h e a c i d f l u o r o -s s u l f a t e s . B u t a s e x p l a i n e d i n s e c t i o n I I I . D . l , X - r a y d i f f r a c -t i o n r e s u l t s o n C y S O ^ F c a n b e i n t e r p r e t e d a s r e f l e c t i n g a v e r y t i g h t p a c k i n g a l o n g t h e c a x i s s h o w i n g n o e v i d e n c e f o r a n i o n s b e i n g t i p p e d o u t o f t h e i n t e r c a l a t e l a y e r . . T h e r e f o r e i t i s r e a s o n a b l e t o a s s u m e t h a t t h e s t e r i c f a c t o r s a l o n g t h e c a x i s b e i d e n t i c a l i n b o t h b i n a r y a n d a c i d f l u o r o s u l f a t e s 1 4 4 a n d a n y d i f f e r e n c e i n p a c k i n g m a y b e a t t r i b u t e d t o t h e d i f f e r -e n c e s i n C o u l o m b i c i n t e r a c t i o n b e t w e e n t h e p o s i t i v e l y c h a r g e d c a r b o n l a y e r s a n d t h e n e g a t i v e l y c h a r g e d i n t e r c a l a t e l a y e r . A l i s t o f v a l u e s d e t e r m i n e d f o r t h e l a y e r s e p a r a t i o n s I c , f o r b i n a r y a n d a c i d f l u o r o s u l f a t e s i s g i v e n i n T a b l e 3 . 5 . T h e a c i d f l u o r o s u l f a t e s s e e m t o s h o w s o m e w h a t l a r g e r v a l u e s f o r I c , p a r t i c u l a r l y w h e n a f a i r l y l a r g e a m o u n t o f a c i d i s p r e s e n t i n t h e i n t e r c a l a t e l a y e r . H o w e v e r i n c o m p o u n d s l i k e C ^ S O g F * 1 . 0 5 H S O 3 F ( A ) , w h e r e t h e a m o u n t o f a c i d p r e s e n t i s r e l a t i v e l y l o w e r t h e o b s e r v e d s a n d w i c h t h i c k n e s s e s a r e s a m e a s t h o s e o f b i n a r y g r a p h i t e f l u o r o s u l f a t e s c o n s i d e r i n g t h e o l i m i t s o f t h e a c c u r a c y f o r t h e s e d a t a w h i c h i s ± 0 . 0 3 A . I t a p p e a r s t h a t t h e p a c k i n g o f i n t e r c a l a t e s b e t w e e n c a r b o n l a y e r s i s r a t h e r t i g h t i n b o t h g r o u p s a n d m o r e s e n s i t i v e c r i t e r i a s h o u l d b e s o u g h t . A n o t h e r p h y s i c a l a s p e c t w h i c h i s a f f e c t e d b y t h e c h a r g e t r a n s f e r i s t h e f o r c e c o n s t a n t o f C - C b o n d i n g r a p h i t e l a y e r s . T h e p o s i t i o n o f t h e l a t t i c e m o d e 6 8 6 9 E 9 „ i s s t a g e d e p e n d e n t ' , b u t t h e f a c t o r s w h i c h a c t u a l l y c o n t r i b u t e t o t h i s s t a g e d e p e n d e n c y i n v o l v e a m o n g o t h e r t h i n g s t h e s t e r i c i n t e r a c t i o n b e t w e e n g r a p h i t e p l a n e s a n d t h e i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m . F o r c o m p o u n d s o f t h e s a m e s t a g e t h e E « 0 v i b r a t i o n a l m o d e s o f t e n a p p e a r w i t h i n 2 g 2 a s m a l l r a n g e , ( 1 0 - 1 5 ) c m 1 a n d t h i s s m a l l d i f f e r e n c e d o e s n o t p r o v i d e s u f f i c i e n t g r o u n d s t o a n y c o n c l u s i v e r e s u l t s . T h e r e -f o r e i n t h i s c o n t e x t t h i s m e t h o d i s a l s o n o t s e n s i t i v e e n o u g h t o d e t e c t t h e d i f f e r e n c e I n c h a r g e t r a n s f e r b e t w e e n b i n a r y a n d a c i d f l u o r o s u l f a t e s o f t h e s a m e s t a g e . O b s e r v a t i o n o f 1 4 5 T A B L E 3 . 5 ; I N T E R L A Y E R S E P A R A T I O N S F O R V A R I O U S G R A P H I T E F L U O R O S U L F A T E S A N D A C I D F L U O R O S U L F A T E S C o m p o u n d s l c [A] R e f e r e n c e a ) B i n a r y f l u o r o s u l f a t e s C 8 S ° 3 F 7 . 8 6 [ 2 8 a ] , [ 2 8 b ] C 7 S 0 3 F 7 . 8 1 ± 0 . 0 3 [ 8 1 ] ( ' t h i s w o r k ) C 1 4 S 0 3 F 1 1 . 1 6 t h i s w o r k b ) A c i d s a l t s C 5 ± 1 H S 0 3 F C 2 l 4 S 0 3 F - n H S 0 3 F 0 4 7 . 9 4 [ 4 9 ] [ 9 5 ] C 1 1 + S 0 3 F - 1 . 0 5 H S O 3 F ( A ) 7 . 8 3 ± 0 . 0 3 t h i s w o r k C 6 . 8 9 S 0 3 F ( V 7 . 8 4 ± 0 . 0 3 t h i s w o r k C 5 . 6 0 S O 3 F ( H ) 0 . 3 7 ( B 2 ) 7 . 9 0 ± 0 . 0 3 t h i s w o r k C 8 . 0 S ° 3 F ( H ) 0 . 6 6 C B 3 ) 8 . 0 1 ± 0 . 0 3 t h i s w o r k 1 4 6 i n t e r c a l a t e m o d e s i s r a t h e r u n c o m m o n a n d s p e c t r a o b t a i n e d i n t h e i n t e r c a l a t e r e g i o n a r e o f p o o r q u a l i t y . A c l e a r d i s t i n c - " t i o n b e t w e e n b i n a r y a n d a c i d f l u o r o s u l f a t e s i s p o s s i b l e o n l y i f a h i g h e r d e g r e e o f r e s o l u t i o n c o u l d b e a c h i e v e d . M i c r o -a n a l y s i s i s o f s o m e w h a t l i m i t e d u s e . T h e o n l y e l e m e n t t h a t a l l o w s d i f f e r e n t i a t i o n b e t w e e n b o t h t y p e s o f g r a p h i t e f l u o r o -s u l f a t e s i s h y d r o g e n . T h e l o w m a s s a n d r a t h e r s m a l l a b u n d a n c e o f h y d r o g e n e x p e c t e d i n t h e a c i d f l u o r o s u l f a t e s p o s e c o n s i d e r -a b l e p r o b l e m s a n d r e d u c e t h e a c c u r a c y o f t h e r e s u l t s . T h e l i m i t o f q u a n t i t a t i v e d e t e r m i n a t i o n o f h y d r o g e n a p p e a r s t o b e 8 2 0 . 1 % i n t h e m e t h o d u s e d f o r a n a l y s i s b y u s , a s f o u n d f o r 2 5 5 1 8 0 s a m p l e E ^ , C g g S 0 3 F ( H ) o . S o f a r t h e s t u d i e s ' ' o n a c i d s a l t s , w h e r e a v a r i e t y o f s i z e s a n d d e g r e e s o f o r d e r o f g r a p h i t e h a v e b e e n i n v o l v e d , h a v e d e p e n d e d o n g r a v i m e t r y t o d e t e r m i n e t h e c o m p o s i t i o n o f t h e s e m a t e r i a l s . . . . . . 1 A v e r y s e n s i t i v e a l b e i t q u a l i t a t i v e t e s t i s t h e H N M R s t u d y o f t h e s e m a t e r i a l s . E v e n t h e c o m p o u n d s h o w e d a b r o a d w e l l r e s o l v e d p r o t o n s i g n a l . T h i s t e c h n i q u e h a s p r e v i o u s l y b e e n u s e d f o r C ^ ^ H S O ^ ^ H ^ S O ^ a n d t w o s i g n a l s h a v e 1 . b e e n o b s e r v e d m t h e H N M R , c o r r e s p o n d i n g t o a n i o n a n d a c i d 1 1 7 1 9 r e s p e c t i v e l y . T h e F N M R o f s o m e o f t h e b i n a r y a n d a c i d f l u o r o s u l f a t e s s y n t h e s i z e d d u r i n g t h i s s t u d y a r e s h o w n i n F i g . ( 3 . 5 . ) a n d t y p i c a l " ' " H N M R s p e c t r a o b t a i n e d f o r a c i d f l u o r o s u l f a t e s 1 9 a r e s h o w n i n F i g . ( 3 . 6 ) . F N M R i s l e s s s u i t e d t o d i f f e r e n -t i a t e i n t e r c a l a t e d S O ^ F a n d H S O g F b e c a u s e r e s o n a n c e s d u e t o S 0 3 F ~ a n d H S 0 3 F a r e o b s e r v e d 1 1 8 a t 3 7 . 4 a n d 4 0 . 6 p p m r e s p e c t i v e l y i n h i g h r e s o l u t i o n s p e c t r a . I n t e r c a l a t i o n o f 147 (b) C I 4S0 SF.(I .05)HS0 SF 50' 0' 50' 100' F I G . 3 . 5 1 9 F N M R S P E C T R A O F A B I N A R Y G R A P H I T E F L U O R O -S U L F A T E A N D G R A P H I T E A C I D F L U O R O S U L F A T E S 148 o 1 1 IO1 1 2 d  r — FIG. 3.6 1H nmr spectra of graphite acid fluorosulfotes 1 4 9 f l u o r o s u l f a t e s i n t o g r a p h i t e c a u s e s a n u p f i e l d s h i f t b y a b o u t 2 0 t o 2 5 p p m f o r s t a g e 1 c o m p o u n d s a c c o m p a n i e d b y a n a r r o w i n g o f t h e r a n g e . T h e s i g n a l s o f i n t e r c a l a t e d S O ^ F a n d H S O ^ F a r e r a t h e r b r o a d a n d o v e r l a p w i t h e a c h o t h e r a s o b s e r v e d i n t h e s p e c t r u m o f C 1 S O g F . 1 . Q 5 H S 0 g F . T h e u p f i e l d s h i f t o n i n t e r -c a l a t i o n i l l u s t r a t e s t h e a c c e p t o r f u n c t i o n o f t h e f l u o r o s u l f a t e s p e c i e s a n d a l l o w s a c l e a r d i s t i n c t i o n b e t w e e n i n t e r c a l a t e d a n d c a p i l l a r y c o n d e n s e d , o r s u r f a c e a d s o r b e d s p e c i e s . B u t a m o n g . t h e . i n t e r c a l a t e d f l u o r o s u l f a t e s a n d a c i d f l u o r o s u l f a t e s 1 9 a c l e a r d i f f e r e n t i a t i o n s e e m s i m p o s s i b l e . N e v e r t h e l e s s F N M R i s u s u a l l y a v e r y u s e f u l t e c h n i q u e i n c h a r a c t e r i z i n g t h e s e 1 m a t e r i a l s . T h e s i g n a l s o b s e r v e d i n H N M R o f a c i d f l u o r o -s u l f a t e s s h o w t h a t t h e r e s o n a n c e o f i n t e r c a l a t e d H S O g F i s s h i f t e d t o a d e s h i e l d e d p o s i t i o n f r o m t h e f r e e a c i d w h i c h i s o b s e r v e d a t 9 . 6 p p m d o w n f i e l d o f T M S . T h e d o w n f i e l d s h i f t o b s e r v e d f o r t h e p r o t o n o f i n t e r c a l a t e d a c i d s u g g e s t s a m o r e a c i d i c p r o t o n i n t h i s s y s t e m t h a n i n f l u o r o s u l f u r i c a c i d w h e r e e x t e n s i v e h y d r o g e n b o n d i n g c a u s e s p o l y m e r i z a t i o n . 1 3 C N M R s p e c t r o s c o p y h a s b e e n o f v e r y l i t t l e u s e i n t h i s m a t t e r s i n c e a l l o f t h e a c c e p t o r c o m p o u n d s g i v e t h e s a m e t y p e o f s p e c t r a w i t h t h e c h e m i c a l s h i f t o f t h e t o p o f t h e s i g n a l a l m o s t a t t h e s a m e p o s i t i o n a s t h a t o f p r i s t i n e 1 1 9 g r a p h i t e w h i c h i s o b s e r v e d a t ^ 5 0 p p m d o w n f i e l d f r o m T M S 1 3 T h e a n a l y s i s o f t h e C N M R s p e c t r a o b t a i n e d i n t h i s s t u d y i s r e s t r i c t e d t o t h e p o s i t i o n o f t h e s i g n a l w i t h r e s p e c t t o t h e e x t e r n a l s t a n d a r d T M S . T h e i n t e r c a l a t i o n c o m p o u n d w h i c h a s d e s c r i b e d b e f o r e s h o w e d a " ' " H N M R s i g n a l i n d i c a t i n g 1 5 0 t h e p r e s e n c e o f H S O ^ F m o l e c u l e s i n a d d i t i o n t o S O ^ F s h o w e d 1 3 o n l y o n e C N M R s i g n a l . T h e p o s i t i o n o f t h i s s i g n a l , w i t h t h e t o p o f t h e p e a k a t 4 2 p p m d o w n f i e l d f r o m T M S , i s i n c l o s e 1 1 9 a g r e e m e n t w i t h t h e s p e c t r a r e p o r t e d f o r s t a g e 1 g r a p h i t e 1 3 a c i d f l u o r o s u l f a t e s . H e n c e t h e C N M R s p e c t r a , d u e t o t h e i r p o o r r e s o l u t i o n , a r e n o t a b l e t o d i s t i n g u i s h b e t w e e n c a r b o n a t o m s o f g r a p h i t e l a y e r s i n d i f f e r e n t e n v i r o n m e n t s w i t h r e s p e c t t o t h e n e i g h b o u r i n g i n t e r c a l a t e l a y e r . T h e r e f o r e . q u a l i t a t i v e e v i d e n c e f o r t h e p r e s e n c e o f a c i d m o l e c u l e s c a n 1 1 9 o n l y b e o b t a i n e d b y H N M R a n d m s o m e c a s e s F N M R a s w e l l . F o r q u a n t i t a t i v e i n f o r m a t i o n o n t h e i n t e r c a l a t e d a c i d m o l e -c u l e s , o n e h a s t o d e p e n d o n m i c r o a n a l y s i s a n d g r a v i m e t r y d e s p i t e t h e i r l i m i t a t i o n s . A s d e s c r i b e d e a r l i e r i n s e c t i o n I I I . D . l , t h e f o r m a t i o n o f f i r s t s t a g e a c i d f l u o r o s u l f a t e s c a n n o t b e a c h i e v e d b y a l l o w i n g t h e f i r s t s t a g e b i n a r y f l u o r o s u l f a t e t o b e e x p o s e d t o a n e x c e s s o f H S O - F , b u t a m o r e s u c c e s s f u l m e t h o d h a s b e e n f o u n d i n t h e a d d i t i o n o f e x c e s s H S O ^ F t o h i g h e r s t a g e b i n a r y f l u o r o s u l f a t e s a c c o r d i n g t o : C S 0 o F + m H S 0 „ F - + C S 0 o F - m H S 0 „ F ( 3 . 1 8 ) n 3 3 n 3 3 H i g h e r s t a g e b i n a r y f l u o r o s u l f a t e s l i k e C - ^ S O g F a r e o b t a i n e d b y t h e p r e s s u r e c o n t r o l l e d r e a c t i o n o f  s 2 0 g F 2 v a p o u r w i t h g r a p h i t e . A d d i n g H S O ^ F t o t h i s c o m p o u n d r e s u l t s i n a s t a g e 1 i n t e r c a l a t i o n c o m p o u n d C ^ S O g F - l . 0 5 H S O g F . A l t h o u g h t h e i n t e r -l a y e r s e p a r a t i o n o f 7 . 8 3 A a n d t h e E 2 g 2 v i b r a t i o n a l b a n d a t 1 6 4 0 c m - 1 a r e n o t v e r y d i f f e r e n t f r o m t h e c o r r e s p o n d i n g d a t a 1 5 1 o b t a i n e d f o r C ^ S O ^ F . , w e i g h t i n c r e a s e a n d N M R s p e c t r a l r e s u l t s c o n f i r m t h e p r e s e n c e o f a c i d m o l e c u l e s i n t h e l a m e l l a r s p a c e s . T h e "^H N M R s p e c t r u m o f t h i s c o m p o u n d s h o w e d a s i n g l e r e s o n a n c e 1 9 a t 1 4 . 3 p p m d o w n f i e l d f r o m T M S a n d t h e F N M R s p e c t r u m s h o w e d b r o a d r e s o n a n c e s a t 1 4 . 0 p p m a n d 3 5 . 9 p p m . T h e r e s o n a n c e a t 1 4 . 0 p p m i s a s s i g n e d t o t h e S O ^ F i o n s i n t e r c a l a t e d i n t o g r a p h i t e . T h e a s s i g n m e n t o f t h e s e c o n d s i g n a l t o t h e i n t e r -c a l a t e d H S O g F m o l e c u l e s i s s u p p o r t e d b y t h e o b s e r v a t i o n t h a t a s a m p l e o f C ^ S O ^ F w i t h s o m e r e s i d u a l s u r f a c e a d s o r b e d H S O ^ F 1 9 . . . s h o w e d a F r e s o n a n c e a t 3 9 p p m , m g o o d p r o x i m i t y t o t h e 1 1 8 c h e m i c a l s h i f t 4 0 . 6 p p m r e p o r t e d f o r l i q u i d H S O ^ F . T h e s i g n a l o b s e r v e d a t 3 9 p p m w o u l d f a d e a n d v a n i s h o n c o n t i n u o u s p u m p i n g o n t h e s a m p l e , b u t t h e s i g n a l o b s e r v e d . a t 3 5 . 9 p p m i n t h e 1 9 F N M R o f C ^ S O ^ F • 1 . 0 5 H S 0 3 F p e r s i s t e d a f t e r p r o l o n g e d e v a c u a t i o n . T h e r e s o n a n c e d u e t o i n t e r c a l a t e d S O F i s s h i f t e d u p f i e l d b y a l m o s t 2 5 p p m f r o m t h e f r e e i o n , b u t i n t e r -c a l a t e d H S O ^ F s h o w s i t s r e s o n a n c e s h i f t e d u p f i e l d o n l y b y 4 p p m f r o m t h a t o f t h e f r e e a c i d . T h i s d i f f e r e n c e c a n b e i n t e r -p r e t e d a s d u e t o d i f f e r e n c e i n c h a r g e t r a n s f e r i n v o l v e d f o r t h e a n i o n a n d n e u t r a l a c i d p r e s e n t i n t h e l a m e l l a r s p a c e s . A n o t h e r r o u t e t o a c i d f l u o r o s u l f a t e s w a s s e e n i n t h e u s e o f m i x t u r e s o f ^2^B^2 an<^ . - ^ S O ^ F . W h e n a n e q u i m o l a r m i x t u r e w h i c h h a d b o t h i n e x c e s s w a s u s e d t o r e a c t , t h e p r o d u c t o b t a i n e d h a d v e r y l i t t l e H S O g F i n t e r c a l a t e d a s d e t e r m i n e d b y m i c r o a n a l y s i s . E s s e n t i a l l y t h e s a m e a n a l y t i c a l r e s u l t s w e r e o b t a i n e d w h e n a m i x t u r e c o n t a i n i n g S 2 0 g F 2 a n d H S O ^ F i n a m o l e r a t i o o f 1 t o 9 , b u t s t i l l w i t h a s t o i c h i o m e t r i c e x c e s s o f 1 5 2 S 0 F 0 p r e s e n t , w a s u s e d f o r i n t e r c a l a t i o n . I t s e e m s t h e r e f o r e 2 b Z t h a t a s l o n g a s s u f f i c i e n t a m o u n t o f S20gF2 i s p r e s e n t i n t h e i n t e r c a l a n t m i x t u r e o x i d a t i v e i n t e r c a l a t i o n t a k e s p l a c e p r e f e r e n t i a l l y a c c o r d i n g t o : 2 n C + S o 0 c F o >- 2 C S 0 o F ( 3 . 1 9 ) Z b z n cs T h e f l u o r o s u l f a t e i o n s o n c e i n t e r c a l a t e d a r e n o t r e a d i l y d i s p l a c e d b y H S O g F w h i c h a g r e e s w i t h t h e e a r l i e r o b s e r v a t i o n i n C - S O - F - H S 0 „ F s y s t e m . A s m a l l a m o u n t o f H S 0 o F i s i n t e r -7 3 . 3 3 c a l a t e d w h e n u s i n g t h e m i x t u r e s c o n t a i n i n g e x c e s s 8 2 0 ^ 2 -M i c r o a n a l y s i s c a n o n l y c o n f i r m t h e p r e s e n c e o f h y d r o g e n b u t t h e a c t u a l a m o u n t a p p e a r s t o b e l o w e r t h a n 0 . 1 % . T h e l a y e r o r e p e a t d i s t a n c e , I o f 7 . 8 4 A a n d t h e i n t r a p l a n a r v i b r a t i o n a l m o d e E „ 0 o b s e r v e d a t 1 6 4 - 1 c m ^  i n t h e R a m a n s p e c t r u m a r e 2 g 2 a l m o s t t h e s a m e a s t h e c o r r e s p o n d i n g v a l u e s f o r t h e b i n a r y f l u o r o s u l f a t e C - , 2S0gF c o n s i d e r i n g t h e e r r o r l i m i t s f o r t h e s e d a t a . T h e o v e r a l l c o m p o s i t i o n o f C g g S O ^ F i s e v i d e n t f r o m b o t h g r a v i m e t r y a n d m i c r o a n a l y s i s . T i g h t e r p a c k i n g i s e x p e c t e d i n t h e i n t e r c a l a t e l a y e r w h e n n e u t r a l a c i d m o l e c u l e s 1 9 a r e p r e s e n t t o d e c r e a s e t h e a n i o n - a n i o n r e p u l s i o n . T h e F N M R o f C g g S O ^ F s h o w e d o n l y o n e s i g n a l a t 1 1 . 3 p p m , b u t d e f i n i t e e v i d e n c e f o r t h e p r e s e n c e o f H S O g F i n t h e g a l l e r i e s i s s e e n i n i t s ^ " H N M R s p e c t r u m w h e r e a s i g n a l a t 1 1 . 5 p p m d o w n f i e l d f r o m T M S w a s o b s e r v e d . T h i s e v i d e n c e f o r t h e p r e s e n c e o f H S O g F t o g e t h e r w i t h t h e s i n g l e r e s o n a n c e o b s e r v e d 1 9 . • f o r F N M R i n d i c a t e a f u n d a m e n t a l d i f f e r e n c e m t h e s t r u c t u r e o f t h i s a c i d s a l t f r o m t h e p r e v i o u s l y d e s c r i b e d a c i d s a l t 1 5 3 C 1 L + S O F - 1 . 0 5 H S 0 3 F - ( A ) . I I I . D . 3 . S T R U C T U R A L M O D E L S O F I N T E R C A L A T E P A C K I N G I N G R A P H I T E  A C I D F L U O R O S U L F A T E S T h e s u c c e s s i v e i n t e r c a l a t i o n o f a s t a g e 2 b i n a r y g r a p h i t e f l u o r o s u l f a t e , C ^ S O ^ F , w i t h H S O ^ F r e s u l t s i n a s t a g e 1 i n t e r c a l a t i o n c o m p o u n d C ^ S O g F ' l . 0 5 H S 0 3 F ( A ) . B a s e d o n o b s e r v a t i o n s i n t h e C ^ S O ^ F - H S O ^ F s y s t e m p r o t o n e x c h a n g e o r i n t e r c a l a t e s u b s t i t u t i o n i n t h e C - ^ S O ^ F - H S O ^ F s y s t e m a p p e a r u n l i k e l y . T h e r e f o r e t h e m o s t l o g i c a l w a y b y w h i c h a s t a g e 2 c o m p o u n d c a n b e t r a n s f o r m e d i n t o a s t a g e 1 a c i d f l u o r o s u l f a t e i n v o l v e s i n c o r p o r a t i o n o f a c i d m o l e c u l e s i n t h e g a l l e r i e s b y a c c o m o d a t i n g t h e m i n t h e p r e v i o u s l y e m p t y a l t e r n a t e l a y e r s . T h i s p a c k i n g m o d e i s n o n - h o m o g e n e o u s a l o n g t h e c a x i s d i r e c -t i o n . H o w e v e r t h e s e p a r a t i o n o f t w o c a r b o n l a y e r s w i t h a H -b o n d e d a c i d i n t e r c a l a t e l a y e r s a n d w i c h e d b e t w e e n t h e m i s n o t e x p e c t e d t o b e v e r y d i f f e r e n t f r o m t h e s e p a r a t i o n w h e r e t h e i n t e r c a l a t e l a y e r i s p r i m a r i l y a n i o n i c , o n a c c o u n t o f t h e s i m i l a r i t i e s o f t h e r e s p e c t i v e i n t e r c a l a t e s . T h e l a y e r r e p e a t d i s t a n c e , I , c a l c u l a t e d f r o m t h e X - r a y p o w d e r d i f f r a c t i o n p a t t e r n w o u l d c o r r e s p o n d t o t h e a v e r a g e s e p a r a t i o n o f c a r b o n l a y e r s . T h e i n t e r c a l a t e l a y e r s c o n t a i n i n g p r i m a r i l y H S O g F m o l e c u l e s a r e e x p e c t e d t o h a v e v e r y t i g h t i n t r a l a y e r p a c k i n g d u e t o e x t e n s i v e h y d r o g e n b o n d i n g a m o n g t h e s e m o l e c u l e s . T h i s 1 i s r e f l e c t e d i n . t h e d o w n f i e l d r e s o n a n c e o b s e r v e d m H N M R . T h e c h a r g e t r a n s f e r f r o m ' g r a p h i t e t o H S O g F m o l e c u l e s s e e m s t o b e v e r y l o w a s e v i d e n c e d b y o n l y a s m a l l u p f i e l d s h i f t i n 1 5 4 1 9 F N M R f o r t h e s i g n a l d u e t o i n t e r c a l a t e d H S O ^ F m o l e c u l e s . O n t h e o t h e r h a n d , a l e s s t i g h t e r p a c k i n g i s e x p e c t e d i n t h e " a n i o n l a y e r " d u e t o e l e c t r o s t a t i c r e p u l s i o n , b u t v e r y h i g h c h a r g e t r a n s f e r f r o m t h e g r a p h i t e t o S O ^ F i o n s i s r e s p o n s i b l e 1 9 f o r t h e s t r o n g e r u p f i e l d s h i f t o b s e r v e d f o r t h e F N M R r e s o n a n c e d u e t o i n t e r c a l a t e d S O ^ F i o n s . S t r u c t u r a l a n d s p e c t r o s c o p i c p r o p e r t i e s o f g r a p h i t e f l u o r o s u l f a t e , a c i d f l u o r o s u l f a t e s a n d r e l a t e d c o m p o u n d s a r e l i s t e d i n T a b l e ( 3 . 6 ) . T h e i n t e r c a l a t i o n c o m p o u n d s f o r m e d b y t h e r e a c t i o n o f g r a p h i t e a n d m i x t u r e s o f S o 0 r F o a n d H S O Q F c o n t a i n a c i d I b I o m o l e c u l e s i n t h e g a l l e r i e s , b u t t h e a m o u n t o f a c i d i n t e r c a l a t e d i s d e p e n d e n t o n t h e a m o u n t o f S 2 0 g F 2 p r e s e n t i n t h e i n t e r c a l a n t m i x t u r e . T h e r e l a t i v e l y s m a l l a m o u n t o f H S O ^ F p r e s e n t i n t h e s e c o m p o u n d s a p p e a r s t o b e m o r e e v e n l y d i s t r i b u t e d o v e r a l l g a l l e r i e s a s e v i d e n c e d b y l 9 F N M R o f C g g S O g F ( B . ^ w h i c h s h o w s o n l y o n e s i g n a l . I n t h e s e s a m p l e s h y d r o g e n b o n d i n g i s m o r e l i k e l y t o o c c u r b e t w e e n H S O ^ F a n d S O ^ F , p r o d u c i n g h i g h e r s h i e l d i n g f o r t h e p r o t o n ( 6 = 1 1 . 5 p p m ) a s a c o n s e q u e n c e o f e x t e n s i v e c h a r g e t r a n s f e r f r o m t h e c a r b o n l a y e r s . T h e m o s t p r o b a b l e s p e c i e s t o b e f o r m e d b y h y d r o g e n b r i d g i n g i s t h e [ H ( S O g F ) 2 ] i o n . T h e p o s s i b l e e x i s t e n c e o f t h i s s p e c i e s i n t h e g a l l e r i e s c a n b e r a t i o n a l i z e d i n t h e f o l l o w i n g m a n n e r : ( i ) O f m a n y p o s s i b l e a c i d a n i o n s i n t h e s y s t e m H S O ^ F - S O g F , t h e a n i o n [ F K S O g F ^ ] i s t h e o n l y o n e s o f a r r e p o r t e d 1 2 0 m a n u m b e r o f a l k a l i m e t a l s a l t s , a n d t h e c r y s t a l 1 2 1 s t r u c t u r e o f t h e c e s i u m s a l t i s k n o w n ( s e e F i g . 3 . 7 ) . 1 5 5 T A B L E .3.6; S T R U C T U R A L A N D S P E C T R O S C O P I C P R O P E R T I E S O F G R A P H I T E F L U O R O S U L F A T E , A C I D F L U O R O S U L F A T E A N D R E L A T E D C O M P O U N D S C o m p o u n d s ° _ 1 1 Q I I c [ A ] A v £ 2 g [ c m x] . 6 ± 3 F [ p p m ] H [ p p m ] C ? S 0 3 F 7 . 8 1 1 6 3 5 1 4 . 8 K S 0 o F r , 3 C s ; 3 8 . 5 C c Q S O „ F .(.B1 ) 6 . y o i 7 . 8 4 1 6 4 0 - 4 3 1 1 . 3 1 1 . 5 C s [ H ( S 0 3 F ) 2 ] ( s ) 3 8 . 0 1 0 . 9 B r C 1 4 S O 3 F - 1 . 0 5 H S O 3 F ( A ) 7 . 8 2 1 6 4 0 1 4 . 0 ; 3 5 . 9 1 4 . 1 H S 0 3 F U ) 4 0 . 6 9 . 8 5 C c c S O „ F ( H ) n o n (B.) 7 . 9 0 1 6 4 0 b . b 3 0 . 3 / z 1 7 . 2 3 6 . 0 9 . 9 B r C 8 . 0 S ° 3 F ( H ) 0 . 6 6 ( B 3 ) 8 ' 0 1 1 6 4 0 2 1 . 0 3 9 . 0 1 4 . 2 7 . 5 B r = B r o a d s i g n a l 1 5 6 F I G . 3 . 7 S T R U C T U R E O F T H E A N I O N ( 0 2 F S O . H . O S F O ) I N C s H ( S 0 3 F ) 2 ( F R O M R E F E R E N C E 1 2 1 ) 157 T h e H b o n d i n t h i s a n i o n a p p e a r s t o b e s y m m e t r i c i n a n a l o g y t o t h e w e l l e s t a b l i s h e d H F - i o n . ( i i ) T h e " ' " H N M R s i g n a l f o r t h e i n t e r c a l a t i o n c o m p o u n d i s a t 1 1 . 5 p p m r e l a t i v e t o T M S , i n r e a s o n a b l e a g r e e m e n t w i t h a v a l u e o f 1 0 . 9 p p m f o u n d f o r C s [ H ( S 0 g F ) 2 ] w h i c h h a d 12 0 b e e n p r e p a r e d a c c o r d i n g t o t h e p u b l i s h e d r e p o r t . . . . 19 ( . i i i ) T h e F N M R s i g n a l f o r t h e c e s i u m s a l t i s f o u n d a t 38 p p m , i n a l m o s t t h e s a m e r e g i o n a s t h e c o r r e s p o n d i n g r e s o n a n c e f o r K S O ^ F ( 3 8 . 5 p p m ) . I t s e e m s l i k e l y t h a t i n t e r c a l a t i o n w i l l p r o d u c e v e r y s i m i l a r u p f i e l d s h i f t s f o r b o t h S O g F a n d [ H ( S 0 3 F ) 2 ] ~ r e s u l t i n g i n o n l y o n e 1 9 F N M R s i g n a l . ( i v ) T h e e x p e r i m e n t a l c o n d i t i o n s , t h e SO^F i o n s p r e s e n t i n a l a r g e e x c e s s , a r g u e a g a i n s t f o r m a t i o n o f a c i d r i c h i n t e r c a l a t e s a n a l o g o u s t o ^ F ^ o r o t h e r s . T h e p r e f e r e n t i a l i n t e r c a l a t i o n o f b i s ( f l u o r o s u l f u r y l ) p e r o d i x e n o t e d d u r i n g t h i s s t u d y a l l o w e d s o m e c o n t r o l o v e r t h e d i r e c t i o n o f t h e r e a c t i o n a n d t h e c o m p o s i t i o n o f t h e f i n a l p r o d u c t b y d r a s t i c a l l y r e d u c i n g t h e a m o u n t s o f S 2 0 g F 2 w i t h HSO^F p r e s e n t i n a l a r g e e x c e s s . T h e a c i d f l u o r o s u l f a t e s B 2 a n d w e r e p r e p a r e d i n t h i s w a y a n d t h e i r c o m p o s i t i o n s w e r e f o u n d t o b e c n c n S 0 o F ( H ) n 0 „ a n d C 0 n S 0 o F ( H ) n c c r e s p e c t i v e l y b y m i c r o a n a l y -5 . 6 0 3 0 .37 8 .0 3 0 . 66 c s i s . T h e l a t t e r p r o d u c t m a y a l s o b e f o r m u l a t e d a s C ^ S O ^ F * 2 H S 0 3 F . 1 5 8 T h e c o m p o s i t i o n o f t h i s c o m p o u n d i s v e r y s i m i l a r t o t h a t o f t h e f i r s t s t a g e a c i d s a l t f o r m e d b y e l e c t r o c h e m i c a l o x i d a t i o n . T h i s s i m i l a r i t y e x t e n d s a l s o t o t h e i n t e r l a y e r s e p a r a t i o n s a s w e l l , s i n c e t h e I v a l u e r e p o r t e d f o r t h e p r o d u c t o f e l e c t r o -o 1' c h e m i c a l o x i d a t i o n o f 7 . 9 4 - A i s i n f a i r a g r e e m e n t w i t h t h e o v a l u e o f 8 . 0 2 ± 0 . 0 3 A d e t e r m i n e d f o r B 3 . N M R s p e c t r a o f t h e c o m p o u n d s B^ a n d i n d i c a t e t h e n a t u r e o f t h e p a c k i n g i n v o l v e d i n t h e i n t e r c a l a t e l a y e r s . A s t h e a m o u n t o f a c i d i n t e r c a l a t e d i s i n c r e a s e d , t h e f i n a l p r o d u c t a p p e a r s t o b e c o m e 1 9 l e s s h o m o g e n e o u s . T h e F N M R s p e c t r a o f t h e c o m p o u n d s B^ a n d B 3 s h o w t w o d i s t i n c t s i g n a l s r a t h e r t h a n o n e a s f o u n d i n . . 1 s a m p l e s w i t h l o w a c i d c o n t e n t . S i m i l a r l y t h e H N M R s p e c t r a o f B 3 s h o w s t w o r e s o n a n c e s , s u p p o r t i n g t h e e x i s t e n c e o f t h e a c i d m o l e c u l e s i n t w o d i s t i n c t i v e l y d i f f e r e n t e n v i r o n m e n t s . 1 9 T h e F N M R s p e c t r u m o f B ^ s h o w s t h e s i g n a l d u e t o i n t e r c a l a -t e d S O g F a t 2 1 . 0 p p m s t i l l w e l l s h i f t e d i n t h e u p f i e l d d i r e c t i o n f r o m 3 8 . 5 p p m o b s e r v e d f o r s o l i d K S O ^ F , b u t t h e m a g n i t u d e o f t h e s h i f t i s l o w e r t h a n t h a t o b s e r v e d f o r s t a g e 1 c o m p o u n d s c o n t a i n i n g S O ^ F o r [ H C S O ^ F ^ ] a l o n e a s i n t e r c a l a t e s W h e n S o 0 r F i s l i m i t e d t o a l o w e r a m o u n t t h a n r e q u i r e d t o f o r m 2 b 2 t h e C y s a l t t h e e x t e n t o f o x i d a t i o n o f c a r b o n p l a n e s i s l i m i t e d a n d s o i s t h e e x t e n t o f c h a r g e t r a n s f e r b e t w e e n c a r b o n a n d i n t e r c a l a t e l a y e r s . T h e r e f o r e t h e d e c r e a s e i n t h e u p f i e l d 1 9 s h i f t o f t h e F r e s o n a n c e o f t h e i n t e r c a l a t e d S O ^ F w i t h t h e d e c r e a s e i n t h e a m o u n t o f S ^ 0 g F 2 u s e d i s n o t s u r p r i s i n g . I n t e r c a l a t e d H S O ^ F ^ a s d i s c u s s e d e a r l i e r , e x p e r i e n c e s l o w e r 1 9 c h a r g e t r a n s f e r t h a n t h e a n i o n a n d i t s F r e s o n a n c e w h i c h 1 5 9 a p p e a r s a t 3 9 . 0 p p m i s n o w n o t v e r y f a r f r o m t h e f r e e a c i d v a l u e o f 4 0 . 6 p p m . T h e a p p e a r a n c e o f t w o s i g n a l s i n b o t h t h e 1 9 1 F a n d H N M R s p e c t r a o f s u g g e s t t h e p r e s e n c e o f b o t h [ H C S O ^ F ) ^ ] a n d h y d r o g e n b o n d e d a c i d m o l e c u l e s i n t h e i n t e r ^ -c a l a t e l a y e r s . T h i s s i t u a t i o n a r i s e s w h e n a p a r t i a l l y o x i d i z e d g r a p h i t e l a t t i c e h a s e n o u g h r o o m i n t h e g a l l e r i e s t o a c c o m o d a t e m o r e a c i d m o l e c u l e s t h a n c o u l d b e h y d r o g e n b o n d e d t o t h e e x i s t i n g S O ^ F i o n s . T h e e x c e s s a c i d t h e r e f o r e c r e a t e s a h e t e r o g e n e o u s p a c k i n g i n t h e i n t e r c a l a t e l a y e r . T h e r e f o r e b y l i m i t i n g t h e a m o u n t o f o x i d a n t ( S 2 0 g F 2 ) p r e s e n t i n t h e r e a g e n t m i x t u r e , , t h e s i m u l t a n e o u s i n t e r c a l a t i o n m e t h o d c a n b e a d o p t e d t o f o r m i n t e r c a l a t i o n c o m p o u n d s v e r y s i m i l a r t o t h o s e p r e p a r e d b y t h e s u c c e s s i v e i n t e r c a l a t i o n m e t h o d . I I I . E . C O N C L U S I O N O x i d a t i v e i n t e r c a l a t i o n o f g r a p h i t e b y b i s ( f l u o r o -s u l f u r y l ) p e r o x i d e p r o c e e d s f a s t e r t h a n t h e i n t e r c a l a t i o n o f f l u o r o s u l f u r i c a c i d . T h e i n t e r c a l a t e d S O ^ F i o n s p r e s e n t i n t h e b i n a r y f l u o r o s u l f a t e s f o r m e d b y t h i s r e a c t i o n a r e s e e m i n g l y n o t r e p l a c e d b y f r e e a c i d m o l e c u l e s a n d d o n o t u n d e r g o p r o t o n t r a n s f e r i n s u s p e n s i o n s m a d e w i t h e x c e s s H S O ^ F . N e v e r t h e l e s s H S O g F c a n b e i n t e r c a l a t e d a l o n g w i t h S O g F i o n s b y t w o p r i n c i p a l w a y s : ( i ) H i g h e r s t a g e b i n a r y f l u o r o s u l f a t e s c a n i n c o r p o r a t e H S 0 „ F t o f o r m s t a g e 1 a c i d f l u o r o s u l f a t e s . 1 6 0 ( i i ) C o i n t e r c a l a t i o n o f S O ^ F w i t h H S O g F f r o m m i x t u r e s c o n t a i n i n g c o n t r o l l e d a m o u n t s o f ^2(~>6^2 a n < 1 a n e x c e s s o f H S 0 3 F w i l l r e s u l t i n t h e f o r m a t i o n o f [ H ( S 0 3 F ) 2 ] ~ i n t h e l a m e l l a r s p a c e s . S y n t h e s i s o f a f a i r l y w i d e r a n g e o f g r a p h i t e a c i d f l u o r o s u l f a t e s c a n b e a c h i e v e d b y u s i n g m i x t u r e s o f c o n t r o l l a m o u n t s o f S r i 0 _ F o a n d a n e x c e s s o f H S 0 „ F . I t a p p e a r s t h a t 2 b 2 o a c i d f l u o r o s u l f a t e s , w i t h a h i g h e r p o s i t i v e c h a r g e d e n s i t y i n t h e c a r b o n l a y e r s t h a n t h o s e p r e p a r e d b y e l e c t r o c h e m i c a l o x i d a t i o n o r u s i n g a n o x i d i z i n g a g e n t , c a n b e s y n t h e s i z e d c o n v e n i e n t l y b y t h i s m e t h o d . 161 C H A P T E R I V G R A P H I T E T R I F L U O R O M E T H Y L S U L F A T E S 1 6 2 C H A P T E R I V G R A P H I T E T R I F L U O R O M E T H Y L S U L F A T E S I V . A I N T R O D U C T I O N T r i f l u o r o m e t h y l s u l f u r l c a c i d , H S O ^ C F g , i s o n e o f t h e \ ; s t r o n g e s t s i m p l e p r o t o n i c a c i d s , c o m p a r a b l e i n t h i s r e g a r d t o f l u o r o s u l f u r i c a c i d . T h e a c i d e x h i b i t s h i g h t h e r m a l s t a b i l i t y e x c e l l e n t i o n i z i n g a b i l i t y a n d s e l f d i s s o c i a t i o n , a n a l o g o u s t o e q u a t i o n ( 4 . 1 ) , d o e s n o t a p p e a r t o o c c u r t h u s r e d u c i n g t h e H S 0 3 F ^ H F + S 0 3 ( 4 . 1 ) c h a n c e f o r . o x i d a t i v e s i d e r e a c t i o n s . I t s a n i o n S O C F i s v e r y o o w e a k l y b a s i c a n d p o o r l y c o o r d i n a t i v e . I n t e r c a l a t i o n r e a c t i o n s i n v o l v i n g H S O ^ C F g w i l l t h e r e f o r e n o t i n v o l v e g r a p h i t e o x i d e o r f l u o r i d e f o r m a t i o n a s a p o s s i b l e s i d e r e a c t i o n . I t s a b i l i t y t o i n t e r c a l a t e b y i t s e l f i s j u d g e d t o b e r a t h e r p o o r . N o r e p o r t s o n t h i s p o i n t c o u l d b e f o u n d . O n t h e o t h e r h a n d e l e c t r o c h e m i c a l i n t e r c a l a t i o n o f H S O g C F g h a s b e e n r e p o r t e d b y 9 6 B o e h m e t . a l . , b y a d o p t i n g t h e c o n v e n t i o n a l t e c h n i q u e s . A l s o t h e o x i d a t i o n u s i n g l ^ C r ^ O d i s s o l v e d i n t h e a c i d r e s u l t s i n 9 6 i n t e r c a l a t i o n o f a c i d a n d t h e a n i o n . T h e i n t e r c a l a t i o n c o m p o u n d s y n t h e s i z e d b y b o t h m e t h o d s w a s f o u n d t o h a v e a m a x i m u m c h a r g e d e n s i t y o n c a r b o n p l a n e s o f a u n i t p o s i t i v e c h a r g e p e r 2 6 c a r b o n a t o m s . T h e c o m p o s i t i o n o f t h e s t a g e 1 c o m p o u n d w a s d e t e r m i n e d b y b u o y a n c y m e a s u r e m e n t s a s 1 6 3 C^Q^O^CY^ 'l.Q3ES0^T. T h i s c o m p o s i t i o n s u g g e s t s a c h a r g e t r a n s f e r f a c t o r o f a p p r o x i m a t e l y 0 . 4 f o r t h i s m a t e r i a l . T h e i n t e r c a l a t i o n o f t h e f r e e a c i d m o l e c u l e s a l o n g w i t h t h e a n i o n i s r e s p o n s i b l e f o r t h e m o d e r a t e l y l o w c h a r g e t r a n s f e r i n v o l v e d . 9 5 S i m i l a r r e s u l t s h a v e b e e n o b s e r v e d i n t h e g r a p h i t e - H S O ^ F c o m p o u n d s p r e p a r e d b y a n o d i c o x i d a t i o n . T o o b t a i n b i n a r y g r a p h i t e t r i f l u o r o m e t h y l s u l f a t e s o n e w o u l d h a v e t o e f f e c t o x i d a t i v e i n t e r c a l a t i o n s i m i l a r t o t h e o n e s d i s c u s s e d i n t h e p r e c e d i n g c h a p t e r , w h e r e b i s ( f l u o r o s u l f u r y l ) p e r o x i d e , S 2 0 g F 2 , h a d f o u n d e x t e n s i v e u s e . H o w e v e r a c o r r e s p o n d i n g r e a g e n t s u c h 1 2 2 a s b i s ( t r i f l u o r o m e t h y l s u l f u r y l ) p e r o x i d e , ( C F 3 S 0 3 ) 2 , o r 1 2 3 c h l o r y l t r i f l u o r o m e t h y l s u l f a t e , C F ^ S C ^ C l , b o t h o f w h i c h c o u l d p r o v i d e S O ^ C F ^ i o n s i n o x i d a t i v e r e a c t i o n s , a r e m o r e d i f f i c u l t t o p r e p a r e t h a n t h e c o r r e s p o n d i n g f l u o r o s u l f a t e a n d e x h i b i t v e r y l i m i t e d t h e r m a l s t a b i l i t y a t 2 5 ° C w h i c h p r e c l u d e s t h e i r u s e i n s y n t h e t i c r e a c t i o n s w h e r e l o n g r e a c t i o n t i m e s a r e a n t i c i p a t e d . T h e s o l v o l y s i s m e t h o d u s u a l l y a d o p t e d t o s y n t h e s i z e t r i f l u o r o m e t h y l s u l f a t e s o f t r a n s i t i o n m e t a l s i n v o l v e t h e c o r r e s -p o n d i n g - h a l i d e s , - c a r b o x y l a t e s , - o x i d e s , a n d - c a r b o n a t e s a s s t a r t i n g m a t e r i a l . B u t b i n a r y g r a p h i t e s a l t s c o n t a i n i n g t h e s e i o n s a s i n t e r c a l a t e s h a v e n o t b e e n s y n t h e s i z e d . H o w e v e r , s o m e w h a t s u r p r i s i n g l y , t h e s o l v o l y s i s o f f l u o r o s u l f a t e s i n a n e x c e s s o f H S O g C F g h a s p r o v i d e d i n a f e w i n s t a n c e s a s y n t h e t i c r o u t e t o n o v e l t r i f l u o r o m e t h y l s u l f a t e s . T h e c o n v e r s i o n o f f l u o r o s u l f a t e s I n t o t r i f l u o r o m e t h y l s u l f a t e s h a s b e e n e l e g a n t l y d e m o n s t r a t e d b y t h e s y n t h e s e s o f A g ( S 0 3 C F 3 ) 2 , A u ( S 0 3 C F 3 ) 3 a n d C s [ A u ( S O g C F g ) ^ ] 1 6 4 1 2 4 f r o m t h e . c o r r e s p o n d i n g f l u o r o s u l f a t e s , a n d t r i f l u o r o m e t h y l -s u l f a t e d e r i v a t i v e s o f i o d i n e h a d b e e n o b t a i n e d f r o m f l u o r o -. . . . 1 2 5 s u l f a t e s m a s i m i l a r q u a n t i t a t i v e c o n v e r s i o n . T h i s c o n v e r s i o n r o u t e a p p e a r s t o h a v e g e n e r a l a p p l i c a b i l i t y . W h i l e t h e n u m b e r o f p u b l i s h e d e x a m p l e s a p p e a r s l i m i t e d , m o r e r e c e n t 1 2 6 w o r k h a s r e v e a l e d q u a n t i t a t i v e c o n v e r s i o n o f f l u o r o s u l f a t e d e r i v a t i v e s o f t i n , p l a t i n u m a n d p a l l a d i u m i n t o t h e c o r r e s p o n d i n g t r i f l u o r o m e t h y l s u l f a t e s . S i n c e H S O ^ F a n d H S O ^ C F ^ a r e o f c o m p a r a b l e a c i d i t y a s s t a t e d e a r l i e r , a n d a l s o e x h i b i t c o m p a r a b l e v o l a t i l i t y , t h e k e y t o a s u c c e s s f u l , q u a n t i t a t i v e c o n v e r s i o n m u s t b e s e e n i n a f o l l o w u p r e a c t i o n b e t w e e n t h e t w o s t r o n g p r o t o n i c a c i d s r e s u l t i n g i n c o m p l e t e d e g r a d a t i o n o f H S O ^ F . S u c h a r e a c t i o n 1 2 7 h a s i n d e e d b e e n o b s e r v e d , f i r s t b y O l a h a n d O y a m a a n d w a s 1 2 8 s u b s e q u e n t l y c o n f i r m e d b y N o f t l e . W h i l e b o t h g r o u p s d i s a g r e e o n t h e v o l a t i l e p r o d u c t s f o r m e d a n d t h e . m e c h a n i s m o f t h i s r e a c t i o n f o r m a t i o n o f v o l a t i l e s s u c h a s C O F ^ , C O ^ , S i F ^ , S C ^ • > C F 3 S 0 3 F a n d C F g S O ^ C F a s r e p o r t e d b y N o f t l e i s o b s e r v e d a l s o d u r i n g t h e c o n v e r s i o n r e a c t i o n s o f m e t a l f l u o r o s u l f a t e s . T h e 1 2 7 p r o p o s e d m e c h a n i s m i n v o l v e s r a t h e r u n s u b s t a n t i a t e d a n d u n d e t e c t e d i n t e r m e d i a t e s l i k e C F 3 + ( s o l v ) o r C F g S O * ( s o l v ) , b u t t h e r e i s n o d o u b t t h a t i t i s t h i s f o l l o w u p r e a c t i o n w h i c h a l l o w s a q u a n t i t a t i v e r e p l a c e m e n t o f S 0 3 F b y S 0 3 C F 3 i n t h e i n s t a n c e s s o f a r s t u d i e d w i t h n o n e o f t h e b y p r o d u c t s i n t e r f e r i n g i n t h e s o l v a t i o n o f a n a l y t i c a l l y p u r e t r i f l u o r o m e t h y l s u l f a t e s . F u r t h e r m o r e , a s i m i l a r d e g r a d a t i o n r e a c t i o n h a s b e e n o b s e r v e d 1 2 4 . f o r S^O^F^ i n H S O g C F g s e e m i n g l y i n i t i a t e d b y t h e o x i d a t i v e 1 6 5 c l e a v a g e , o f t h e S - C b o n d i n H S O g C F g , c a u s i n g t h e f o r m a t i o n o f C F g S O g F . S i n c e r e p l a c e m e n t o f i n t e r c a l a t e d S O g F - b y t h e l a r g e r S O g C F g m a y r e s u l t i n r e d u c t i o n o f g r a p h i t e u n d e r S 2 0 g F 2 r e l e a s e , t h i s a s p e c t b e c o m e s i m p o r t a n t w h e n c o n t e m p l a t i n g t h e s o l v o l y s i s o f C ? S 0 3 F i n H S 0 3 C F 3 . T w o f u r t h e r i n t r o d u c t o r y c o m m e n t s m a y b e m a d e : ( a ) S u c c e s s f u l a n d q u a n t i t a t i v e s o l v o l y t i c c o n v e r s i o n o f e . g . A u ( S 0 3 F ) ~ a n d S n ( S 0 3 F ) g ~ , b o t h r a t h e r s t a b l e t o w a r d s s o l v e n t i n t e r a c t i o n i n H S O ^ F a s i n d i c a t e d b y 1 9 . . . t h e i r F N M R r e s o n a n c e s , m a y i n d i c a t e t h a t i n t e r m e d i a t e f o r m a t i o n o f H S 0 3 F m a y n o t b e n e c e s s a r y a n d c o o r d i n a t e d S 0 3 F g r o u p s i n c o o r d i n a t i v e l y s a t u r a t e d e n v i r o n m e n t s m a y u n d e r g o d e g r a d a t i o n a s w e l l . E v e n t h o u g h C ^ S O ^ F h a d b e e n f o u n d t o b e i n e r t i n H S O ^ F a s d i s c u s s e d i n t h e p r e c e d i n g c h a p t e r , t h i s d o e s n o t e x c l u d e a p o s s i b l e s o l v o l y t i c d e g r a d a t i o n o f i n t e r c a l a t e d S O ^ F b y H S O ^ C F ^ r e s u l t i n g i n n e t i n t e r c a l a t e e x c h a n g e . ( b ) A s m e n t i o n e d i n c h a p t e r I t h e r e i s o n l y o n e r e p o r t e d p r e c e d e n t o f a s u c c e s s f u l i n t e r c a l a t e e x c h a n g e 2 5 r e a c t i o n a n d i t c a n b e d e s c r i b e d a s ? C X . m H X + ( n + m ) H X ' • C X ' . m H X ' + ( n + m ) H X n n C 4 . 2 ) A c o n v e r s i o n o f g r a p h i t e b i s u l f a t e t o g r a p h i t e p e r ' c h l o r a t e b y t h i s m e t h o d h a s b e e n a c h i e v e d s i n c e i t 1 6 6 i s , f a v o u r e d b y t h e r m o d y n a m i c a n d k i n e t i c c o n d i t i o n s . I V . B . S Y N T H E T I C R E A C T I O N S T h e s y n t h e s e s o f g r a p h i t e t r i f l u o r o m e t h y l s u l f a t e s w e r e c a r r i e d o u t b y r e a c t i n g b i n a r y g r a p h i t e f l u o r o s u l f a t e s , m a d e f r o m S P l g r a p h i t e o r H O P G w i t h a n e x c e s s o f H S O ^ C F g . I V . B . l . S Y N T H E S I S O F A S T A G E 1 G R A P H I T E T R T F L U O R O M E T H Y L S U L F A T E I n a t y p i c a l r e a c t i o n a b o u t 1 0 m l o f f r e s h l y d i s t i l l e d H S 0 3 C F 3 w a s d i s t i l l e d i n t o a r e a c t o r c o n t a i n i n g 2 9 7 . 3 m g o f C y 2 ^ ^ 3 F p r e p a r e d e a r l i e r b y r e a c t i n g l i q u i d S ^ O g F ^ w i t h S P l g r a p h i t e . T h i s m i x t u r e w a s m a g n e t i c a l l y s t i r r e d a t r o o m t e m p e r a t u r e f o r 4 8 h o u r s . T h e b l u e c o l o u r o f t h e s o l i d p e r s i s t e d a n d a s l i g h t i n c r e a s e i n v a p o u r p r e s s u r e i n t h e r e a c t i o n v e s s e l w a s n o t e d . T h e p r o d u c t s , v o l a t i l e a t r o o m t e m p e r a t u r e , w e r e c o l l e c t e d a n d t h e i r I R s p e c t r u m w a s r e c o r d e d . T h e e x c e s s a c i d w a s r e m o v e d i n v a c u o a n d t h e s a m p l e e x p o s e d t o a d y n a m i c v a c u u m . W h e n t h e s a m p l e r e a c h e d c o n s t a n t w e i g h t , 2 8 8 . 1 m g o f a b l u e p o w d e r y s o l i d w a s o b t a i n e d . T a k i n g i n t o a c c o u n t a s m a l l w e i g h t l o s s d u e t o r e a c t i o n o f t h e P y r e x v e s s e l , g r a v i m e t r y i n d i c a t e d a c o m p o s i t i o n o f C ^ 2 Q ^ ^ 2 ^ 3 ' M i c r o a n a l y s i s f o r C , S a n d F s u g g e s t e d a c o m p o s i t i o n o f C 1 2 . 2 S ° 3 C F 3 ' M I C R O A N A L Y S I S : C S F F / S C a l c u l a t e d f o r C 1 2 2 S 0 3 C F 3 I % ] 5 3 . 6 2 1 0 . 8 3 1 9 . 2 9 3 . 0 0 F o u n d I % ] 5 3 . 2 3 1 0 . 5 5 1 8 . 9 6 3 . 0 2 1 6 7 A l t e r n a t e p r e p a r a t i o n s s u g g e s t e d , c o m p o s i t i o n s o f ^ S O g C F g a n d C ^ - j ^ g S O g C F g b a s e d o n g r a v i m e t r y a n d m i c r o a n a l y s i s f o r C . N e i t h e r h y d r o g e n n o r r C F ^ w e r e d e t e c t e d d u r i n g m i c r o a n a l y s i s o f t h e s e s a m p l e s . T h e e v o l u t i o n o f C F ^ i s o f t e n o b s e r v e d w h e n f l u o r o c a r b o n s o r f l u o r i n e c o n t a i n i n g g r a p h i t e i n t e r c a l a t i o n c o m p o u n d s a r e a n a l y z e d W h e n t h e s a m p l e s o f C y S O ^ F m a d e f r o m H O P G w e r e r e a c t e d w i t h H S O g C F g t h e p r o d u c t s o b t a i n e d w e r e o f t e n c l e a v e d a l o n g t h e c - a x i s d i r e c t i o n . T h i s m i g h t h a v e b e e n c a u s e d b y t h e e x o t h e r m i c n a t u r e o f t h e s o l v o l y s i s r e a c t i o n . H o w e v e r , f i r s t s t a g e c o m p o u n d s m a d e f r o m H O P G a l s o s h o w e d g r a v i m e t r i c c o m p o s i t i o n s o f ^ C - ^ S O g C F g a f t e r e x p o s u r e t o a d y n a m i c v a c u u m f o r s e v e r a l h o u r s t o r e m o v e t h e a c i d m o l e c u l e s t r a p p e d b e t w e e n t h e c l e a v e d l a y e r s . T h e X - r a y p o w d e r d i f f r a c t i o n p a t t e r n ( T a b l e 4 . 1 ) o f t h e g r a p h i t e t r i f l u o r o m e t h y l s u l f a t e , 2 ^ ^ 3 ^ F 3 ' s n o w e c ^ ^ ^° b e p r i m a r i l y o f s t a g e 1 c o m p o s i t i o n w i t h t h e l a y e r r e p e a t d i s t a n c e I o f 8 . 1 2 ± 0 . 0 3 A . c I V . B . 2 . S Y N T H E S I S O F G R A P H I T E T R I F L U O R O M E T H Y L S U L F A T E S O F S T A G E S > 2 T h e s a m p l e s o f g r a p h i t e t r i f l u o r o m e t h y l s u l f a t e s o f h i g h e r s t a g e s w e r e p r e p a r e d f r o m H O P G s i n c e t h e s e s a m p l e s w e r e t o b e u s e d f o r e l e c t r i c a l c o n d u c t i v i t y m e a s u r e m e n t s . H O P G p i e c e s w e r e f i r s t r e a c t e d w i t h S20gF2 v a p o u r t o f o r m g r a p h i t e f l u o r o s u l f a t e s o f t h e c o m p o s i t i o n s C - ^ £ ^ 0 ^ a n d C2Q g S ' O ^ F a s i n d i c a t e d b y t h e i n c r e a s e i n w e i g h t o f t h e s a m p l e s . L a r g e r 1 6 8 T A B L E 4 . 1 : T H E c A X I S R E P E A T D I S T A N C E I O F S T A G E 1 G R A P H I T E c T R I F L U O R O M E T H Y L S U L F A T E , C ^ S O g C F g 0 0 £ l i n e i n X - r a y D i f f r a c t i o n I n t e n s i t y I ( A ) 0 0 1 V W 8 . 1 1 5 0 0 0 2 V S 8 . 1 3 5 0 0 0 3 W 8 . 1 0 6 9 0 0 4 M 8 . 1 0 9 2 0 0 5 W 8 . 1 1 7 0 S = S t r o n g M = M e d i u m W = W e a k V S = V e r y S t r o n g V W = V e r y W e a k 1 6 9 a m o u n t s o f H S O ^ C F g t h a n s t o i c h i o m e t r i c a l l y r e q u i r e d t o r e a c t w i t h t h e i n t e r c a l a t e d S O ^ F w e r e d i s t i l l e d o v e r t h e s e s a m p l e s a n d a l l o w e d t o r e a c t f o r 4 8 h o u r s . T h e e x c e s s a c i d w a s r e m o v e d e i t h e r b y v a c u u m f i l t r a t i o n o r i n a d y n a m i c v a c u u m . T h e G I C s f o r m e d w e r e m a i n t a i n e d i n a d y n a m i c v a c u u m f o r s e v e r a l h o u r s . T h e c o m p o s i t i o n s o f t h e s e m a t e r i a l s w e r e c a l c u l a t e d f r o m t h e w e i g h t c h a n g e s o b s e r v e d a f t e r e v a c u a t i o n a n d t h e c h a n g e s i n t h i c k n e s s o f t h e s a m p l e s i n d i c a t e d t h e i r d o m i n a n t s t a g e i n d i c e s . T h e f o l l o w i n g t a b l e s u m m a r i z e s t h e c o m p o s i t i o n s a n d s t a g e i n d i c e s f o r t h e g r a p h i t e t r i f l u o r o m e t h y l s u l f a t e s , w h i c h a r e p r i m a r i l y o f s t a g e s 2 a n d 3 . T h e g r a p h i t e f l u o r o s u l f a t e s u s e d a s s t a r t i n g m a t e r i a l s a r e a l s o i n d i c a t e d w i t h t h e c o r r e s p o n d i n g p r o d u c t s . T a b l e 4 . 2 : G R A P H I T E T R I F L U O R O M E T H Y L S U L F A T E S C S T A G E S 2 , 3 ) a £ C o m p o s i t i o n ) S t a g e i n d e x o ( i ) C 2 Q 5 S 0 o C F 3 2 . 0 5 2 C 1 4 . 2 S 0 3 F 2 C 3 0 . 5 S 0 3 C F 3 1 ' S S 3 C 2 0 . 3 S O 3 F X - 1 5 3 a t a n d t a r e t h e t h i c k n e s s o f H O P G a n d t h e G I C r e s p e c t i v e l y o b t h e d o m i n a n t s t a g e i n d e x i n d i c a t e d b y t h e v a l u e o f / 1 ) 170 Although, the samples of stages 2 and. 3 prepared by t h i s method were a l s o maintained In a dynamic vacuum f o r s e v e r a l days, i t i s s t i l l p o s s i b l e that some fre e a c i d molecules might remain i n t e r c a l a t e d along w i t h the anion. Therefore the s o l v o l y s i s method Is not s u i t a b l e to synthesize graphite t r i -f l u o r o m e t h y l s u l f a t e s of stage i n d i c e s >2 completely f r e e of ac i d molecules. However, as i n d i c a t e d In Table 4.2, samples of higher stages c o n t a i n i n g the anion SO^CF^ as the p r i n c i p a l i n t e r c a l a t e can be prepared by the s o l v o l y s i s of graphite f l u o r o s u l f a t e s of the same stage. IV.C. RESULTS AND DISCUSSION S o l v o l y s i s of C^SO^F i n a la r g e excess of HSO^CF^ r e s u l t s i n a s u c c e s s f u l q u a n t i t a t i v e replacement of the SO^F by SOgCF^ to give C^SOgCFg with the concomitant . change i n ~. the composition of the f i n a l product. The f i r s t step i n the s o l v o l y s i s of graphite f l u o r o s u l f a t e by HSO^CFg can be explained by equation (4.3) with the formula t i o n of the graphite f l u o r o s u l f a t e as CgSO^F adopted f o r convenience. 6C oS0 oF + 4HS0oCF„ —> 4CloS0„CF„ + 4HS0 oF + S o0_F o 8 3 3 3 12 d o d I b I (4.3) This r e a c t i o n would lead to complete conversion without producing mixed products i f the byproducts are removed from the r e a c t i o n mixture. The observed increase i n vapour pressure during the r e a c t i o n r e s u l t s from the f u r t h e r r e a c t i o n of the 171 byproducts HSOgF and S 20gF 2 with. HSQgCF.g •• B i s C f l u o r o s u l f u r y l ) peroxide, as mentioned e a r l i e r , has 12 7 been found to o x i d i z e the S-C bond i n HS0 3CF 3 while HSO^F 12 8 and HSOgCFg are reported to form a number of v o l a t i l e byproducts. Because HSO^CFg was used i n l a r g e molar excess i n t h i s r e a c t i o n compared to the amount of SO F group present one would a n t i c i p a t e such f u r t h e r r e a c t i o n . In a l l r e a c t i o n s i n v o l v i n g graphite f l u o r o s u l f a t e s and t r i f l u o r o m e t h y l s u l f u r i c a c i d a s l i g h t pressure increase was noted i n d i c a t i n g the presence of v o l a t i l e byproducts. The gas phase I.R. spectrum of these compounds showed bands a t t r i b u t a b l e to CF 3OS0 2F, CF 30S0 2CF 3, F2CO,. S0 2, S i F ^ and C0 2 as r e p o r t e d 1 2 1 4 e a r l i e r f o r s o l v o l y s i s r e a c t i o n s i n v o l v i n g t r a n s i t i o n metal f l u o r o s u l f a t e s and HSOgCFg. I t should be pointed out that published rep o r t s on degradation of f l u o r o s u l f a t e species i n an excess of HS0 oCF o i n v o l v e H S 0 o F 1 2 7 ' 1 2 8 and S o 0 c F o 1 2 4 . The conversion 3 3 3 .2 b 2 r e a c t i o n s of t r a n s i t i o n metal f l u o r o s u l f a t e s and more recent 2-work on s o l v o l y t i c a l l y s t a b l e anions l i k e [Sn(S0 3F)g] suggest coordinated or c o v a l e n t l y bonded f l u o r o s u l f a t e groups may be r e a c t i v e i n t h i s manner since the intermediate formation of e i t h e r HS0 oF or So0_F„ i s not obvious. S i m i l a r conclusions 3 2 b 2 may extent to the conversion of C^SO^T i n t o C 1 2 S 0 3 C F 3 because CySOgF had been found,., as discussed i n the previous chapter, s o l v o l y t i c a l l y s t a b l e i n HSOgF. The colour of the f i r s t stage graphite f l u o r o s u l f a t e CySOgF does not appear to change during the conversions, the observed weight changes were al s o not prominent. This i s i n 172 good agreement with equation (4.3) according to which the change i n weight should he the d i f f e r e n c e of (2 x mol. weight of C 1 2 S 0 3 C F 3 = 586.39) and (3 x mol. weight of CgSC^F = 585.43) This small d i f f e r e n c e could be e a s i l y obscured by the s l i g h t weight l o s s of the r e a c t i o n v e s s e l during the r e a c t i o n . The SiF, formation observed i n the I.R. spectrum provides evidence f o r the r e a c t i o n of the Pyrex v e s s e l . The f i n a l product i s st a b l e i n a dynamic vacuum, the v o l a t i l e products as w e l l as the excess HSO^CFg were removed by continuous evacuation. Since gravimetry.in t h i s case i s i n c o n c l u s i v e , t h e best evidence f o r the complete replacement of the SO^F ions by SO^CF^ i s seen i n the m i c r o a n a l y s i s ; i n p a r t i c u l a r i n the S:F r a t i o of about 1:3. The formulat i o n of C^SOgCF^ i s c o n s i s t e n t with both m i c r o a n a l y s i s and gravimetry. STRUCTURAL AND SPECTROSCOPIC PROPERTIES The c a x i s l a y e r repeat distance of the stage 1 i n t e r -o c a l a t i o n compound C^SOgCF^ increases from 7.81 to 8.12 A when the SOgF ions are replaced by SO^CF^ . While t h i s l a y e r o separation i s not very d i f f e r e n t from the value of 8.036 A r e p o r t e d 9 6 f o r the a c i d s a l t C*S0„CF ~ • 1. 63HSO„CF„ , s u f f i c i e n t Z b o o o o strong d i f f e r e n c e s between both compounds are apparent. The extent of o x i d a t i o n of the carbon l a y e r s i n the compound C^SOgCF^ was determined i o d o m e t r i c a l l y , employing a method 12 9 published o r i g i n a l l y by Riidorff and Hoffmann . The r e s u l t s of t h i s experiment suggest one p o s i t i v e charge f o r about 12.2 graphite carbon atoms, while c o n t r o l l e d anodic o x i d a t i o n of 173 graphite i n HSOgCFg y i e l d s a value of C*^ . In a d d i t i o n , ther--S t o C (graphite) r a t i o 1:12.45 determined by mic r o a n a l y s i s i n C-^SO-^CFj i s d i f f e r e n t from 1:10.1 c a l c u l a t e d f o r the compound C S0oCF„:1.63HS0„CFo. I t seems that anion-anion ^ 2 6 3 3 3 3 r e p u l s i o n w i t h i n the i n t e r c a l a t e l a y e r i s higher i n C-^SOgCF^ than i n the a c i d s a l t . The lower r e p u l s i o n i n the l a t t e r m a t e r i a l i s due to the presence of free a c i d molecules which could form hydrogen bridges with the anions.•'Graphite f l u o r o -s u l f a t e s of d i f f e r e n t compositions v a r y i n g between CySO^F and C-^SOgF, a l l produced the compound C-^SO^CFg o n s o l v o l y s i s . Therefore i t can be concluded t h a t i t i s the l i m i t i n g composi-t i o n to accomodate SO^CF^ ions i n the same i n t e r c a l a t e l a y e r . The increased s i z e of the SO^CF^ ion over SO^F appears t o + + be the p r i n c i p a l reason f o r the change from Cy to C^2 o n i n t e r c a l a t e exchange. The s t r u c t u r e of SO^CF^. i o n has been determined with 13 0-13 2 d i f f e r e n t c a tions . The molecular geometry of t h i s i o n could be described by a staggered c o n f i g u r a t i o n as shown i n F i g . (4.1). The volume occupied by t h i s i o n could be approxima-o ted to an asymmetric e l l i p s o i d of about 6.1 A maximal l e n g t h , c o n s i s t i n g of a smaller CF 3 group and a l a r g e r S0 3 moiety. The reported i n t e r a t o m i c distances w i t h i n the SO^ group of the S0 3CF 3" ion f a l l i n the range of 1.428 - 1.443 A 1 3 0 , which o d i f f e r s very l i t t l e from the S-0 bond di s t a n c e of 1.43 ± 0.01 A reported 1"'' 4 f o r SOgF i o n . The thickness along the c a x i s required to accomodate the carbon atoms of bounding carbon ° 15 lay e r s i s 3.35 A . Therefore an o r i e n t a t i o n of the S0 3CF 3 174 FIG. 4.1 STRUCTURE OF S0 3CF 3 ION (FROM REF. 127) 175 ions i n the i n t e r c a l a t e l a y e r with t h e i r S-C bonds p a r a l l e l o to c a x i s would r e q u i r e a sandwich th i c k n e s s of at l e a s t 9.45 A while the arrangement with the S-C bonds p a r a l l e l to the o b a s a l plane would r e q u i r e only 7.81 A, as described e a r l i e r f o r the i n t e r c a l a t e d SO^F i o n . The observed sandwich t h i c k -o ness of 8.12 A f o r C^SO^CF^ i s c l o s e r to the minimum separa-t i o n of the bounding carbon l a y e r s r e q u i r e d to accomodate a l l SOgCF^ ions i n the i n t e r c a l a t e l a y e r with t h e i r S-C bonds p a r a l l e l to the basal plane. I t could also be noted that when + - * - . going from CySOgF to C-^SOgCFg "the degree of o x i d a t i o n of carbon l a y e r s i s reduced and t h i s would r e s u l t i n reduced Coulombic a t t r a c t i o n between graphite and i n t e r c a l a t e l a y e r s c o n t a i n i n g SO^CF^ ion s . Therefore the i n t e r c a l a t e l a y e r s i n ^12^^3<"F3 m a y b e l o o s e l y packed between the carbon l a y e r s as opposed to the t i g h t packing observed i n C^SO^F. S i m i l a r 2 8b conclusions have been reported f o r some binary graphite s a l t s with various h e x a f l u o r o m e t a l l a t e anions as I n t e r c a l a t e s . Therefore the most l i k e l y arrangement of SO^CF^ ions i n the i n t e r c a l a t e l a y e r would be with the S-C bond p a r a l l e l to the basal planes, while a small increase i n the sandwich thickness observed could be a t t r i b u t e d to a l o o s e l y packed arrangement along the c a x i s d i r e c t i o n due to the lowering i n Coulombic a t t r a c t i o n between carbon and I n t e r c a l a t e l a y e r s . 19 Consistent with the a n a l y t i c a l r e s u l t s , the F NMR spectrum of C^SO^CFg showed complete absence of resonances i n the reg i o n K10 ppm r e l a t i v e to CFC13> where i n t e r c a l a t e d SOgF- i s u s u a l l y observed. Samples which had been evacuated 176 f o r a short time only, showed two broad resonances i n the r e g i o n c h a r a c t e r i s t i c of CF^ resonance; Continuous evacuation causes the gradual disappearance of one of these s i g n a l s , a t t r i b u t e d t o surface adsorbed or c a p i l l a r y condensed HSO^CFg and a poorly resolved t r i p l e t centered at -71.1 ppm remains. Th e f i n a l product, O^SO^CF^ does not show a detectable s i g n a l i n "^H NMR, confirming the complete removal of a c i d molecules. 19 The F NMR spectrum of s e v e r a l separate preparations of C^SOgCFg showed the type of resonance shown i n F i g . (4.2). Each component of the t r i p l e t had a l i n e width at h a l f height of about 800 Hz'.:. The observation of such a poorly r e s o l v e d t r i p l e t f o r the i n t e r c a l a t e d SO^CF^ i s a t t r i b u t e d to the d i p o l a r i n t e r a c t i o n s between C-F bonds. However, the NMR 13 3 13 4 spectrum obtained using a l i n e narrowing pulse sequence ' showed a s i n g l e t . These pulse sequences average the p o p u l a t i o n of spins In a l l d i r e c t i o n s and hence suppress the d i p o l a r i n t e r a c t i o n s i n the p o l y c r y s t a l l i n e sample. The c o l l a p s i n g of the t r i p l e t i n t o a s i n g l e t when the d i p o l a r i n t e r a c t i o n s are removed confirms i t s assignment as a CF^ resonance. The chemical s h i f t of the center of the resonance due to the i n t e r c a l a t e d S0 oCF o i s observed at -71.1 ppm as opposed to the chemical s h i f t of ^-46.0 ppm of the center of the broad resonance observed f o r s o l i d AgSOgCFg. This observation i s i n agreement wi t h the s h i f t i n the higher f i e l d d i r e c t i o n u s u a l l y observed f o r the i n t e r c a l a t e d species. The r e s u l t s of ESR measurements on C-^SOgCFg are 13 5 —13 7 c o n s i s t e n t w i t h previous r e p o r t s " on GICs. A s i n g l e 1 7 7 I j The^Fnmr. spectrum of solid CgSOsCfj — -71,1 direct observation T r b) with line narrowing pulse sequence -i r - 1 r 2 0 0 - 1 0 0 0 8 values rel.to CFCI3 i r 1 0 0 F I G . 4.2 178 resonance with g value of 2.0030 was observed f o r powder samples of C 1 2 S 0 3 C F 3 . This i s very c l o s e to the g value 2.002 3 of 13 8 fr e e e l e c t r o n supporting the f a c t t h a t the observed spin resonance o r i g i n a t e d from the conduction e l e c t r o n s w i t h i n the graphite l a y e r s . The asymmetric Dysonian l i n e shape of the ESR spectrum of C-^SOgCFg i s t y p i c a l of systems with aromatic 13 7 r a d i c a l c a t ions such as acceptor GICs where the s k i n depth 139 140 i s much l e s s than the sample thi c k n e s s ' The v i b r a t i o n a l spectra were found to be u s e f u l f o r both determining the stage index of the compound and to i d e n t i f y the i n t e r c a l a t e . The sample c h a r a c t e r i z e d by m i c r o a n a l y s i s and gravimetry as C^2 2 S 0 3 C F 3 showed i t s E 2 g 2 v i t > r a " t i ° n a l mode at 1641 cm 1 i n i t s Raman spectrum. The s h i f t of t h i s mode towards higher frequency by 5 2 cm 1 from t h a t of p r i s t i n e g r aphite confirms t h a t i t i s p r i m a r i l y of stage 1 composition. This mode was observed as a s i n g l e t showing that a l l graphite planes were I d e n t i c a l w i t h respect to the f o r c e constant of the C-C bonds due to t h e i r i d e n t i c a l environment w i t h respect to the neighbouring i n t e r c a l a t e l a y e r s . The I.R. a c t i v e E^ u v i b r a t i o n a l mode observed at 1588 cm 1 f o r HOPG, was not observed f o r a sample of C^SOgCFg prepared from the same m a t e r i a l . This v i b r a t i o n a l mode i s absent f o r stage 1 i n t e r -j 141 c a l a t i o n compounds V i b r a t i o n a l modes assignable to the i n t e r c a l a t e are also observed i n both Raman and I.R. spectra of C-^SOjCFg. Li k e many sulfur-oxygen compounds t r i f l u o r o m e t h y l s u l f a t e s are good Raman s c a t t e r e r s and w e l l r e s o l v e d spectra of s o l i d 179 samples are f r e q u e n t l y observed. In a d d i t i o n , Raman bands due to the i n t e r c a l a t e have been observed f o r the a c i d f l u o r o -7 4 s u l f a t e of g r a p h i t e , C ^ Q H S O ^ F . In t h i s study the observed bands f a l l i n t o the region of 700 to 1300 cm 1 and are a t t r i -buted to s t r e t c h i n g v i b r a t i o n s of i n t e r c a l a t e d HSO^F. The i n t e r c a l a t e r e g i o n of the Raman spectrum of C-^SOgCF^ covers the r e g i o n of 57 0 t o 12 3 0 cm 1 w i t h the bands i n the lower frequency region superimposed on a s l o p i n g background caused by fluorescence. I n t e r e s t i n g l y r a t h e r broad and somewhat poor re s o l v e d absorption bands are observed i n IR spectra of the f i l m s of t h i s sample, both i n r e f l e c t a n c e and tra n s m i s s i o n geometries, using a r o u t i n e spectrophotometer without any s i g n a l enhancement by F o u r i e r transform techniques. A l i s t i n g of the frequencies of the bands observed i n Raman and I.R. spectra of C-^SOgCFg i s given i n Table (4.3) and the i n t e r -c a l a t e r e g i o n of the I.R. spectrum of C^SO^CFg i s shown i n F i g . (4.3). The bands observed i n the mid I.R. region are c l e a r l y assignable to the i n t e r c a l a t e and these bands show reasonable correspondence to the Raman bands observed f o r the same compound. A notable feature i n the I.R. spectrum i s the absence of bands above 13 0 0 cm 1 and i n Raman spectra the only band observed above t h i s frequency i s c l e a r l y assigned to the E 2g2 - 1- a" t :" t :i c e m°de. This along with the absence of bands assignable to S-OH v i b r a t i o n s (^ 9 50 cm 1 ) argue against the presence of HSO^CFg i n the sample. -1 7 4 A band at 9 60-92 0 cm has been observed m the Raman spectrum of C, nHS0 F and. v i b r a t i o n s due t o OH groups 180 TABLE 4.3: VIBRATIONAL SPECTRA OF. C ^ S O ^ C r ^ Raman Infrared Infrared Approximate Scattering Reflection Transmission AgSOgCFg Description Av(cm "Srel Int. v(cm ^ ) Int. v(cm ^ ) Int. v(cm 1) 1634 s E 0 l a t t i c e 2g2 mode 1250 vs 1270 vS0 3 asym 1220 s,b 1260--1230 b 1218 s , sh 1237 vCF 3 asym 1190 b 1188 s 1189 s 1167 vCF 3 asym 1125 s unassignec 1020 m 1020 (m) 1025 (s) 1043 v S 0 3 sym 7 3 5 v. w 768 w 768 vw 760 v SC 610-603 w,b 635 m 639 m 647 6 SO 3 sym 570 w 575 w 578 w 582 579 6CF 3 asym 515 m 520 w 525 515 6 S 0 3 asym See Ref. 143. S o l i d AgSOgCFg has a d d i t i o n a l fundamentals at 351, 320 and 217 cm"1. Abb r e v i a t i o n s : s = strong, m = medium, w = weak, v = very, b = broad, sh = shoulder, sym = symmetric, asym = asymmetric. FIG. 4.3 The Infrared Spectrum of C SOCF r 12 3 3 WAVENUMBER (CM'') 182 are quite, prominent i n I.R. spectra. While the v i b r a t i o n a l spectra of graphite t r i f l u o r o m e t h y l s u l f a t e support i t s -. molecular s t r u c t u r e being described by the i o n i c f o r m u l a t i o n C-jtjSOgCF^ , due to the poor r e s o l u t i o n and d i f f i c u l t i e s i n d e t e c t i n g bands i n the low frequency region of both I.R. and Raman spectra a d e t a i l e d assignment of a l l v i b r a t i o n a l modes i s not p o s s i b l e . A group frequency assignment f o r the SO^CF^ 142-144 ion had m the past, been reported to be d i f f i c u l t even f o r simple s a l t s such as NH^SO^CF^ > due to the near coincidence and the v i b r a t i o n a l mixing of CF^.and SO^ funda-mentals. The observation of r a t h e r broad bands f o r C-^SO^CF^ could be a t t r i b u t e d i n part t o these f a c t o r s , however even a compound such as the a c i d f l u o r o s u l f a t e , C ^ Q H S O ^ F does not seem to show narrower'bands i n the Raman spectrum. Although a complete v i b r a t i o n a l spectrum could not be obtained f o r C^SOgCFg , i t i s s t i l l p o s s i b l e to make some l i m i t e d comments based on the v i b r a t i o n a l frequencies observed f o r the i n t e r c a l a t e d SO^CF^ i o n . Comparing these 143 with the frequencies reported f o r AgSO^CFg (see Table 4.3), a small but n o t i c e a b l e s h i f t to lower frequencies f o r bands predominantly due to SO s t r e t c h i n g motions i n the i n t e r c a l a t e d i o n i s obvious. But the bands due t o v i b r a t i o n a l motion of the CF 3 group (at ^119 0 cm - 1) or the S-C bond (at ^7 7 0 cm"1) seem to be the same as the f r e e i o n or even s h i f t e d to higher frequencies. This evidence seems to i n d i c a t e some p o l a r i z a t i o n e f f e c t s : i n the S0 3CF 3 i o n , which apparently cause the weakening of S-0 bonds. S i m i l a r frequency s h i f t s 183 were observed e a r l i e r i n C^.QHSQ3F where a decrease i n the 7 4 extent of p - d bonding i n the S-0 bond was proposed . But s i m i l a r conclusions could not be reached f o r the i n t e r c a l a t e d S0 3CF 3 i o n , because g e n e r a l l y v i b r a t i o n a l s p e c t r a of oxyanions are notorious f o r c a t i o n dependent frequency s h i f t s . F i n a l l y , a sharp band of medium i n t e n s i t y observed i n the Raman spectrum of C-^SOgCF^ at 1125 cm 1 could not be assigned to any i n t e r c a l a t e mode. This band d i d not have a corresponding I.R. band. Since the SO^CFg ion i s of r a t h e r low symmetry and the mutual e x c l u s i o n p r i n c i p l e could not be invoked, a reasonable assignment of t h i s band to any i n t e r c a l a t e mode i s not p o s s i b l e . IV. D. CONCLUSION', The graphite t r i f l u oromethylsulf ate C-^SOgCFg i s a binary stage 1 i n t e r c a l a t i o n compound.distinctively d i f f e r e n t from the a c i d s a l t s obtained by e l e c t r o c h e m i c a l o x i d a t i o n or by using an e x t e r n a l o x i d i z i n g agent. The s u c c e s s f u l conversion of graphite f l u o r o s u l f a t e to t h i s compound through s o l v o l y s i s not only emphasizes the p o t e n t i a l of the former as a s u i t a b l e s t a r t i n g m a t e r i a l f o r the syntheses of novel graphite i n t e r -c a l a t i o n compounds, but also expands the scope of the s o l v o l y -s i s method, h i t h e r t o used f o r syntheses of t r a n s i t i o n metal compounds, to the synthesis of l a m e l l a r m a t e r i a l s . 184 CHAPTER V INTERACTION OF FLUOROSULFATES AND FLUORIDES IN THE INTERCALATE LAYERS OF THE GICs 18 5. CHAPTER V INTERACTION OF FLUOROSULFATES AND As, Sb FLUORIDES IN THE INTERCALATE LAYERS OF THE GICs V.A. REACTION OF ANTIMONY PENTAFLUORIDE WITH GRAPHITE  FLUOROSULFATES V.A.I. INTRODUCTION I n t e r c a l a t i o n of antimony p e n t a f l u o r i d e , SbF^, i n 145 graphite was f i r s t reported i n 1973 . Subsequently the composition of the r e s u l t i n g GICs was determined as C^' g_g SbF r with c a x i s p e r i o d i c i t i e s I = ' 8.41 + 3 . 3 5 (n-1 )!".A/..where 5 ^ c " ' . 146 147 n i s the stage index of the sample ' . Although the studies of graphite-SbF^ compounds were i n i t i a t e d before i n v e s t i g a t i o n s of graphite-AsF^ systems, there are s i m i l a r d i f f e r e n c e s i n opinion regarding the change i n o x i d a t i o n s t a t e of the metal atom during i n t e r c a l a t i o n and the extent of 148 charge t r a n s f e r . E a r l y studies of the chemical p r o p e r t i e s i n t e r c a l a t e d SbF,- apparently i n d i c a t e d the f u n c t i o n of the host m a t e r i a l , g r a p h i t e , to be s i m i l a r to that of an i n e r t s o l v e n t , with the GICs o f f e r i n g a decided advantage over the viscous l i q u i d SbF^. The i n t e r c a l a t i o n of SbF^ i s u s u a l l y c a r r i e d ;©ut by the d i r e c t i n t e r c a l a t i o n method using the vapour or l i q u i d phase reagent, where HF could be the only impurity and even 147 that would not change the nature of the GIC . Chemical 186 14-5 146 analyses of t h i s m a t e r i a l showed ' a Sb:F r a t i o of 1:5 121 149 however, Sb MOssbauer spectra have suggested the presence of both S b ( I I I ) and Sb(V), produced by the e q u i l i b r i u m (5.1), 6 3 which i s formulated i n analogy to the e q u i l i b r i u m found f o r graphite-AsFg systems. 3SbF c + 2e ^ 2SbF c + SbF 0 (5.1) o 6 3 The above e q u i l i b r i u m a l s o e x p l a i n s the e v o l u t i o n of SbFj- as 2 9 the only thermal decomposition product from t h i s GIC However the exact p o s i t i o n of the e q u i l i b r i u m and the r o l e of SbFj- i n these systems are subjects of much debate. 150 . . . 1 9 Spectroscopic studies using wide l i n e F NMR e x h i b i t e d chemical s h i f t s that were i n d i c a t i v e of SbF r or SbF r b 6 and not SbF^ present as i n t e r c a l a t e s i n the sample. The 151 composition of t h i s GIC can the r e f o r e be expressed as C+(SbF„ ) J-(SbF r), n .... , where f denotes the i o n i z a t i o n parameter, m 6 f 5 (1-f) v 148 151 152 The value of f has been determined ' ' by various methods to be approximately 0.2 and a composition of g 2+ 151 Cg' 7 (SbF-g) Q • 2^ SbF,-) has been proposed f o r the stage 1 compound. Due to the low i o n i c content of graphite-SbF,- compounds and the very low v o l a t i l i t y of SbF g i t i s not easy to remove the i n t e r c a l a t e d SbF 5 and r e - i n t e r c a l a t e the r e s u l t i n g m a t e r i a l . The amount of SbF g i n these compounds could only be increased by o x i d a t i v e i n t e r c a l a t i o n i n v o l v i n g strong o x i d i z i n g agents. Previous attempts to obtain binary + graphite hexafluoro antimonates have i n v o l v e d n i t r o n i u m , N0 2, 187 or ni.tros.oni.um, N0 +, s a l t s , of hexafluoro antimonate (V). Both of these reagents have to be d i s s o l v e d i n s u i t a b l e s o l v e n t s , which I n e v i t a b l y also i n t e r c a l a t e i n t o g r a p h i t e . Two c o n f l i c t -ing r eports on the products of the r e a c t i o n of graphite and 15 3 NC^SbFg i n dry nitromethane are found. While i n one case 2 S L . 6 the simultaneous i n t e r c a l a t i o n of s o l v e n t , SbF c and N0 o bF 2 7 was suggested, the other r e p o r t claimed graphite hexafluoro antimonates corresponding to stages 1 to 8. However, subsequent-154 l y a f t e r chemical analyses, t h i s c l a i m was r e v i s e d r e p o r t i n g an " i d e a l composition" of 3 n^bFg (CH^NC^) 7 ^ o r a stage n sample. The increased carbon to i n t e r c a l a t e r a t i o i n these compounds again l i m i t s the c a r r i e r d ensity i n the carbon l a y e r s . The r e a c t i o n of graphite with NOSbFg i n the same 15 4 solvent d i d not proceed beyond a stage 2 GIC . Not unexpect-edly the successive treatment of graphite f i r s t w i t h AsFj- and then with NO~SbFn d i s s o l v e d i n CH oN0 o r e s u l t e d i n a complex 2 b 3 2 mixture c o n t a i n i n g AsF g , AsF^, AsFg," SbFg and SbF 5 as i n d i c a t e d by l 9 F NMR52. A novel approach aimed at a b e t t e r understanding of the nature of graphite-SbFg - compounds i s to devise a f e a s i b l e s y n t h e t i c route to graphite s a l t s with SbFg as the only i n t e r c a l a t e . A s i m i l a r compound, CgAsFg , has been prepared by B a r t l e t t et a l . 6 3 by r e a c t i n g graphite with O^AsFg . The a b s t r a c t i o n of the SOgF ion i n C^SOgF by s o l v o l y s i s i n an excess of SbFj- appeared as a p o s s i b l e route f o r the synthesis of graphite hexafluoro antimonate iy)-< C^SbFg . I n t e r e s t i n t h i s s o l v o l y s i s r e a c t i o n arose f o r s e v e r a l reasons: 188 Ci.) The .potential s t a r t i n g m a t e r i a l , CySO^F i s e a s i l y synthesized by r e a c t i n g graphite with S„O rF„. Z b Z ( i i ) The p r e v i o u s l y discussed s u c c e s s f u l q u a n t i t a t i v e replacement of the SO^F i o n by SO^CF^- through s o l v o l y s i s i n an excess of HSO^CF^. ( i i i ) The e x i s t i n g precedents f o r the intended s o l v o l y s i s i n 155 156 SbF 5 ' , as i l l u s t r a t e d by the r e a c t i o n of various 15 5 interhalogen f l u o r o s u l f a t e s according to equation (5.2), i n d i c a t e d that t h i s r e a c t i o n could be extended to the graphite f l u o r o s u l f a t e C^SO^F. I B r 2 S 0 3 F + 4SbF 5 »- I B ^ S b ^ ^ + S b 2 F g S 0 3 F (5.2) ( i v ) The i n t e r f e r e n c e of SbF^ could h o p e f u l l y be avoided i n the above r e a c t i o n . The byproduct S b 2 F g ( S 0 3 F ) , a (SO^F) bridged unsymmetric dimer has been found to e x h i b i t vapour pressures of ^5-10 Torr at room temperature and t h e r e f o r e could be removed i n a dynamic vacuum. V.A.2. SOME PROPERTIES' OF ANTIMONY PENTAFLUORIDE Antimony p e n t a f l u o r i d e , SbF 5, i s a c o l o u r l e s s , extremely 157 viscous (460 c p . ) l i q u i d which melts at 8.3°C and b o i l s 15 8 at l14l°C . This suggests considerable a s s o c i a t i o n of the molecules, presumably by c i s F-bridges. The vapour pressure 189 15 9 of ShFj. at 2 0°C i s 4 t o r r and p r e l i m i n a r y molecular weight determinations i n the gas phase have i n d i c a t e d the existence i £ n of trimers at 152°C and dimers up to 252°C . In t h e l l i q u i d 159 phase, even though IR and Raman studies suggested a t r i g o n a l bipyramidal s t r u c t u r e , f u r t h e r work showed that n e i t h e r t h i s nor a square pyramidal s t r u c t u r e f o r SbFj. as a monomer were r e a s o n a b l e 1 6 1 ' 1 6 2 . The 1 9 E NMR spectrum of l i q u i d SbF 5 near i t s melting p o i n t i n d i c a t e d a c i s Sb-F-Sb bridged polymeric 16 3 s t r u c t u r e . But upon warming the sample f i r s t to 2 5°C and then to 80°C, r a p i d f l u o r i n e exchange, presumably i n t e r m o l e c u l a r , 16 3 164 takes place ' . In "^ he s o l i d phase, the octahedral c o o r d i n a t i o n around the Sb atom of SbF^ has been confirmed by 16 5 c r y s t a l s t r u c t u r e , where t e t r a m e r i c u n i t s were found l i n k e d together by c i s f l u o r i n e bridges V.A.3. SYNTHESIS OF GRAPHITE HEXAFLUORO ANTTMONATE (V) In a t y p i c a l r e a c t i o n 0.2043 g of SP1 graphite was reacted with a large excess (about 10.0 ml) of S o0 F 0 at room ° z b Z temperature f o r 24 hours. The excess of ^^^l W a S r e m o v e < ^ i n vacuo and a stage 1 m a t e r i a l of approximate composition Cy j-SO^F was obtained. To t h i s sample about 10.0 ml of SbF^ were d i s t i l l e d i n vacuo. This mixture was warmed to 45°C to f a c i l i t a t e mixing of the reactants and maintained f o r 6 days at t h i s temperature. The v o l a t i l e r e a c t i o n products were c o l l e c t e d i n a monel metal c e l l w i t h AgCl windows and the IR spectrum was recorded. The spectrum i n d i c a t e d the presence of SbF c and S b o F n S 0 o F 1 5 5 i n the v o l a t i l e products. A l l the b i y o 190 v o l a t i l e , products were removed, i n vacuo and the s o l i d was exposed to a dynamic vacuum u n t i l constant weight was reached. Gravimetry, assuming complete replacement of i n t e r c a l a t e d SOgF by SbFg ions,suggested a composition of ?SbFg : while m i c r o a n a l y s i s i n d i c a t e d a composition about Cg ^SbFg. The product appeared dark blue, c h a r a c t e r i s t i c of lower stage acceptor GICs. M i c r o a n a l y s i s : -C Sb F T o t a l F /Sb C a l c u l a t e d f o r C 0 nSbF r [%] 28.94 36.70 34.36 100.00 6.00 o . U b Found [%] 28.57. 36.96 34.21 99.74 5.89 A s i m i l a r r e a c t i o n using HOPG as the s t a r t i n g m a t e r i a l r e s u l t e d i n a blue-black product of approximate composition Cj gSbFg as i n d i c a t e d by gravimetry. Higher stage m a t e r i a l s were also prepared from HOPG f o r e l e c t r i c a l c o n d u c t i v i t y measurements. However, due to the problems i n removing a l l i n t e r c a l a t e d SbFg i n a dynamic vacuum the higher stage GICs contained both SbF_ and SbF r as i n t e r c a l a t e s . 6 b V.A.4. RESULTS AND DISCUSSION (a) SYNTHESIS AND GENERAL DISCUSSION The f o r m u l a t i o n , CgSbFg , agrees very w e l l w i t h the mic r o a n a l y s i s r e s u l t s . The a n a l y t i c a l data obtained on t h i s i n t e r c a l a t i o n compound i n d i c a t e three important aspects 191 regarding the s o l v o l y s i s r e a c t i o n : ( i ) The absence of detectable amounts ;of s u l f u r as i n d i c a t e d by the t o t a l carbon, antimony and f l u o r i n e content of the product shows that the SO^F ions have been q u a n t i t a t i v e l y removed as Sb^FgSOgF, i n analogy with the 155 reported precedents , under approximate r e t e n t i o n of the extent of o x i d a t i o n of carbon l a y e r s . ( i i ) The q u a n t i t a t i v e course of the s o l v o l y s i s r e a c t i o n argues against the presence of appreciable amounts of C-F or C-0 linkages i n C^SO^F. These groups would have been r a t h e r r e s i s t a n t to s o l v o l y s i s . ( i i i ) The i n t e r c a l a t e l a y e r s of the new GIC appear to c o n s i s t of SbFg ions as the predominant species. The observed F/Sb r a t i o of 5.89 i s s l i g h t l y lower than the expected value of 6.0 f o r C~SbFr . This might have been caused o o by the formation of small amounts of polyanions such as S b 2 F 1 1 ~ i n the l a m e l l a r spaces. As i n d i c a t e d by r e a c t i o n (5.2) the formation of t h i s polyanion during t h i s s o l v o l y s i s can be expected. On the other hand the discrepancy observed i n the F/Sb r a t i o might be simply due to a n a l y t i c a l d i s c r e p a n c i e s caused by the formation of r a t h e r unreactive CF^ during the course of the a n a l y t i c a l procedures. The e l i m i n a t i o n of CF^ might have a l s o caused a s l i g h t lowering i n the observed carbon and f l u o r i n e contents. The mild c o n d i t i o n s 192 r e q u i r e d f o r t h i s r e a c t i o n avoids any p o s s i b i l i t y of f l u o r i n a t i o n of the carbon planes, i n contrast to gas 151 phase r e a c t i o n s which i n v o l v e much higher temperatures Cupto 300°C) and show evidences f o r C-F formation. (b) STRUCTURAL AND SPECTROSCOPIC STUDIES One of the primary concerns associated with the s o l v o l y s i s of graphite f l u o r o s u l f ate by SbF,- i s the q u a n t i t a t i v e replacement of a l l SO^F i o n s . The s o l v o l y s i s r e a c t i o n can be 19 followed by observing the F NMR spectra of the m a t e r i a l . 19 F NMR parameters f o r graphite hexafluoro antimonates and some r e l a t e d compounds are l i s t e d i n Table (5.1). The i n t e r -c a l a t i o n compound CgSbFg made from SP1 graphite showed a s i n g l e resonance at -121 ppm and a sample of approximate composition C"12 2^^^6 ^according to gravimetry) made from HOPG showed a s i n g l e peak at -128 ppm with respect t o CFClg. The chemical s h i f t of t h i s resonance i s c l o s e r to those of SbF,- and SbFg than SbFg. Also these spectra do not show any evidence f o r the formation of polyanions such as Sb^F^-^ . However the very small d i f f e r e n c e s i n chemical s h i f t s of SbF,- and SbF r i n the b b high r e s o l u t i o n spectra suggests that the resonances of i n t e r -c a l a t e d SbF 5 and SbFg could not be d i s t i n g u i s h e d by t h e i r chemical s h i f t s i n room temperature s o l i d s t a t e NMR spectra. + 0 2 -In f a c t the GIC of composition C g j ^ S b F g ^ Q 2<'St>F5''o 8 prepared by r e a c t i n g graphite w i t h SbF,- shows only one s i g n a l with almost the same chemical s h i f t as l i q u i d SbF,- (see Table 5.1). But the GIC which contains SbFg" as the only f l u o r i n a t e d 193 TABLE 5.1: I 9 F NMR DATA FOR GRAPHITE HEXAFLUORO ANTIMONATES AND RELATED COMPOUNDS Compound Chemical S h i f t (ppm r e l . to CFC1 3) Reference SbFr -112.0 163 SbF, 86.0 163 SbF, -115.8 166 -112.5 52, 151 C 2 3 ( S b F g ) ( C H 3 N 0 2 ) 1 < 7 -1214.1 52, 154 C 8 S b F 6 " -121.0 This Work C 1 2 . 2 S b F 6 -128.0 This Work 194 i n t e r c a l a t e shows resonance i n the higher f i e l d region ' The samples prepared by the s o l v o l y s i s method, C gSbF g and ^12 2 ^ F 6 ' a S r e e w i " t h t h i s chemical s h i f t of the resonances due to I n t e r c a l a t e d SbF g i n these samples seem to support the 52 stage dependency reported e a r l i e r f o r these systems. The absence of resonances i n the regions where SO gF or C-F groups are observed, confirms that the s o l v o l y s i s r e a c t i o n completely removes SO^F ions as v o l a t i l e byproducts and no f l u o r i n a t i o n of the graphite l a t t i c e takes place during t h i s r e a c t i o n . The i n t e r p r e t a t i o n of C gSbF g as a f i r s t stage compound i s based on: (I) X-ray powder d i f f r a c t i o n , where the strongest l i n e was a t t r i b u t e d to 002 r e f l e c t i o n s and a c-axis l a y e r o separation of 8.19 ± 0.03 A was deduced from s e v e r a l (002.) r e f l e c t i o n s . ( I I ) The E„ _ v i b r a t i o n a l mode of t h i s compound was observed 2g2 at 1636-1640 cm 1 i n i t s Raman spectrum. The replacement of SO^F ions by SbF g seems to have o caused an increase of 0.3 8 A i n the c-axis l a y e r separation of the stage 1 m a t e r i a l . As shown i n Table (5.2), the T value o of 8.19 A f o r C 0SbF 0 i s i n close agreement with the values o fa determined f o r s e v e r a l graphite hexafluoro m e t a l l a t e s . However the f i r s t stage compound C g ^_g 5SbF^ which i s now accepted to be of the composition C g 7 ( S b F g ) Q 2 ( S b F 5 ) Q g shows a l a r g e r s e p a r a t i o n of l a y e r s . The arrangement of i n t e r c a l a t e s i n t h i s 195 TABLE 5.2: LAYER REPEAT. DISTANCE ALONG THE c=AXIS. ( I ) FOR STAGE. .1. GRAPHITE. HEXAFLUOROMETALLATE.S.,. C„MF n 6 Composition I C^ A' ) Reference C Q n Q O s F c 8.10 28b o , I d b C 7 > g 8 I r F 6 8.05 28b C0AsF„ 8.10 63 » b C 2 3AsF 6(.CH 3N0 2 ) 2 7 . 99 175 C 8 . 7 ( S b V o . 2 ( S b V o . 8 8 ' 4 6 1 4 6 ' 1 4 7 C 0SbF. 8.10 This Work 8 6 196 compound has been i n v e s t i g a t e d by energy d i s p e r s i v e X-ray d i f f r a c t i o n (EDXD) and an in-plane s t r u c t u r a l model has been n 167 proposed . The i n t e r c a l a t e l a y e r s c o n s i s t of SbF,- molecules and SbFg ions arranged i n such a manner that the i o n i z a t i o n f a c t o r f reaches an average value of 0.2. Both a t i g h t e r packing of the i n t e r c a l a t e s and a l s o a lower charge d i s t r i b u - ' t i o n might have caused the l a r g e r i n t e r l a y e r separation i n t h i s compound. The increased charge d e n s i t y , s i m i l a r to other CoMF r , leads to increased Coulombic a t t r a c t i o n between the o b i n t e r c a l a t e and graphite l a y e r s i n C o S b F c r e s u l t i n g i n a o b t i g h t e r packing along the c-axis d i r e c t i o n . The s i m i l a r i t i e s i n the compositions as w e l l as the i n t e r l a y e r - separations of CgSbFg with other graphite hexa-f l u o r o m e t a l l a t e s , CgMFg , i n d i c a t e the p o s s i b i l i t y of f u r t h e r s t r u c t u r a l s i m i l a r i t i e s among these compounds. In the case of C^AsF- , a hexagonal u n i t c e l l w i t h the AsF„ ions c l o s e l y 8 6 6 packed with t h e i r Cg axes aligned along the c-axis of carbon 6 3 planes has been reported . A s i m i l a r s i t u a t i o n may be found i n the case of c tsbF_ as w e l l . The small increase i n the I 8 6 c value of the l a t t e r compound compared to that of CgAsFg may b e a t t r i b u t e d to the s l i g h t l y l a r g e r SbFg i o n . In i s o s t r u c -+ t u r a l s a l t s with common cations -C CH_N i n th i s , case - i n t e r -b 6 o nuclear separations f o r M-F bonds of 1.77 and 1.87 A have been 16 8 — — reported f o r AsF g and SbF g r e s p e c t i v e l y . A s u i t a b l e 169 precedent f o r t h i s case would be KSbFg, the c r y s t a l s t r u c t u r e of which i s shown i n f i g . ( 5 . 1 ) . In t h i s s a l t the SbFg octahedra are or i e n t e d w i t h t h e i r Cg axes i n the v e r t i c a l 197 (B) 3 6 8 135 8 12 1.35 • 3.35/j ( i ) I ( c a l c ) s 9.73 A ( i i ) I ( c a l c ) = 8.17 s FIG. 5.1 (A) CRYSTAL STRUCTURE OF KSbFg (Ref. 169) (B) POSSIBLE ORIENTATIONS OF SbFg" IONS IN THE INTERCALATE LAYER 198 d i r e c t i o n . Assuming a s i m i l a r o r i e n t a t i o n f o r SbF r Ions i n b + CcSbF„ , the f o l l o w i n g deductions regarding the space r e q u i r e -o b ments f o r the i n t e r c a l a t e l a y e r s can be made: ( i ) The thickness of carbon l a y e r s could be assumed to be unchanged during i n t e r c a l a t i o n since there was no evidence of C-F bond formation. Hence the e f f e c t i v e 1 ° thickness of — (3.35) A on e i t h e r side of the i n t e r c a l a t e 2 l a y e r would be occupied by the bounding carbon l a y e r s . ( i i ) The thic k n e s s of the i n t e r c a l a t e l a y e r with the SbFg ions o r i e n t e d w i t h t h e i r C g axes p a r a l l e l to the c-axis [See f i g . 5 . 1 ( B ) ( i i ) ] would be given by [2 Tp + A. (d^_p)], where Yp i s the radius of the f l u o r i n e atom and i s the length of Sb-F bonds. Using the values of 1.35 A ° 16 9 and 1.84 A f o r Yp a n ^ d^ p r e s p e c t i v e l y the th i c k n e s s o of the i n t e r c a l a t e l a y e r can be c a l c u l a t e d to be 4.8 2 A. o This would suggest a sandwich thickness (T ) of 8.17 A s f o r a very t i g h t packing between carbon and i n t e r c a l a t e o l a y e r s . The observed i n t e r l a y e r s e p a r a t i o n of 8.19 A f o r C QSbF c agrees c l o s e l y w i t h t h i s f i g u r e . A d i f f e r e n t o b arrangement of the SbFg ions such as f o r example with t h e i r C^ axes p a r a l l e l to the c-axis of graphite as shown i n f i g . 5.1(B)(1) would r e q u i r e a sandwich t h i c k -o ness ( I g ) of 9.73 A. Therefore a t i g h t packing along the c-axis d i r e c t i o n with the SbFg ions a l i g n e d as shown i n f i g . 5 . 1 ( B ) ( I i ) i s proposed f o r C gSbFg. 199 V-B. ' REACTION OF ARSENIC PENTAFLUORTDE WITH GRAPHITE FLUOROSULFATE V.B.I. INTRODUCTION The i n t e r c a l a t i o n of a r s e n i c p e n t a f l u o r i d e , AsF,-, i n t o 17 0 graphxte was f i r s t reported by S e l i g and coworkers . This system has since then been studied e x t e n s i v e l y f o r two major reasons: ( i ) The unusually high e l e c t r i c a l c o n d u c t i v i t y reported f o r the r e s u l t i n g GIC has aroused much i n t e r e s t i n these m a t e r i a l s ( i i ) While the composition f o r stages 1 to 3 i s given by the general formula Cg nAsF^, with the c-axis l a y e r repeat o distance I = (4.75 + 3.35 n) A, where n i s the stage c ' 61 index , the o x i d a t i o n state of the i n t e r c a l a t e and the extent of charge t r a n s f e r have produced much d i s c u s s -6 7 ion ' i n the past. The e q u i l i b r i u m according t o equation (5.3), f i r s t 6 3 171 proposed by B a r t l e t t and coworkers ' appears to have been g e n e r a l l y accepted, but i t s exact p o s i t i o n and hence the degree of charge t r a n s f e r involved i n t h i s system are s t i l l 6—8 subject of much debate 3AsF c + 2e ^ 2AsF c + AsF 0 (5.3) b b o Evidence f o r the presence of A s F 3 and AsFg i n graphite 200 i n t e r c a l a t e d by AsF^ was observed in. the As-K s h e l l absorption edge spectra of t h i s m a t e r i a l w h i l e p r e f e r e n t i a l e v o l u t i o n of AsF,- from t h i s m a t e r i a l i n a dynamic vacuum could be explained 6 3 by the r e v e r s a l of the e q u i l i b r i u m shown above . I f a l l of the i n t e r c a l a t e d AsF,- molecules are reduced to form AsFg a n d AsF' s p e c i e s , the composition of the stage 1 compound would 3 be C*°' 6 7(AsF ~ ) 0 / 0 ( A s F 0 ) . , / 0 . But the 1 9 F NMR spectrum of t h i s 1U 6 2 / 0 3 1/3 59 compound i n d i c a t e d the presence of AsFg or AsFg but not AsF g This may i n d i c a t e that the proposed r e d u c t i o n of AsF,- molecules should take place to a very small extent l e a v i n g most of i t i n the molecular form as AsFg o r , as has been argued, i f the AsF^ resonance i s broadened and or overlapping with As(V)-F resonances. These s i t u a t i o n s are p o s s i b l e according to the 5 9 f o l l o w i n g r e a c t i o n sequence proposed by Ebert et a l . IOC + 1.25 AsF c 2 4 ° C ) C*° - 1(AsF ~ ) n 1 ( A s F c ) 1 , ( A s F q ) n n Q b 10 6 0.1 b 1.1 o O.Ub (5.4) V a c U U m> c!°':1(AsF - ) . , (AsFj.) n q ( 5 . 5 ) 1U b U . l b U . a A somewhat c l e a r e r p i c t u r e i s expected, regarding the i d e n t i t y of the i n t e r c a l a t e and the amount of i o n i c content, i n graphite hexafluoroarsenates(V), because only As(V) s o l e l y i n the form of AsF- should be present i n the i n t e r c a l a t e l a y e r s . Therefore the extent of charge t r a n s f e r i s d i r e c t l y i n d i c a t e d by the stoi c h i o m e t r y . Subsequently d i f f e r e n t compositions and s t r u c t u r a l types, depending on the methods 201 of p r e p a r a t i o n , have been reported f o r the stage 1 graphite hexafluoroarsenate(V). C y c l i c pumping on the stage 1 compound C DAsF r to remove AsF 0 and A s F r , followed by f u r t h e r r e a c t i o n o b d o with more AsF^ leads to a product of the composition of 171 172 C-^AsFg ' . The composition of the product obtained t h i s 17 3 . way has r e c e n t l y been r e v i s e d to be C-^AsFg with an m t e r -o l a y e r separation- of 7.60 A. F l u o r i n a t i o n of CgAsF^ with elemental f l u o r i n e 2 8 o r o x i d a t i v e i n t e r c a l a t i o n of graphite w i t h 0 2AsFg according to equation (5.6) leads to C QAsFg as the l i m i t i n g composition. 8C + o!AsF ~ * c t A s F ~ + 0 o (5.6) 2 b o b 2 Recently some doubt has surfaced regarding the course of such f l u o r i n a t i o n r e a c t i o n s . Reacting graphite with a mixture of N0„BF,, and LiAsF- d i s s o l v e d i n nitromethane r e s u l t s i n 2 4 b + - 17 5 C 2 3 ( A s F g )(CH 3NC> 2) 2 as the stage 1 product according t o : 23C + NO* • C 2 + 3 + N0 2 (5.7) C* + AsF c (CH„N0 o) o • C 0 +o(AsF c )(CH„N0 o) o (5.8) 2o 6 3 2 2 23 b i l l Simultaneous i n t e r c a l a t i o n of F during the d i r e c t f l u o r i n a t i o n 171 174 176 of higher stage C„ AsF c ' ' or even the formation of & & 8n 5 covalent C-F bonds on f l u o r i n a t i o n 1 1 2 ^ a ^ ' 1 7 7 and the c o i n t e r -17 5 c a l a t i o n of s o l v e n t , e.g. nitromethane are some of the complications enroute to graphite hexafluoroarsenates. 202 The graphite.-AsFg i n t e r c a l a t i o n compounds and the graphite hexafluoroarsenates e x h i b i t d i s t i n c t i v e l y d i f f e r e n t basal plane e l e c t r i c a l c o n d u c t i v i t i e s . The i n t e r c a l a t i o n A r~> A T1 v. ^ 4- ,174,178-180 . compounds Cg nAsFg have been reported to e x h i b i t 181 " m e t a l l i c " c o n d u c t i v i t i e s . Even though i n i t i a l claims of s p e c i f i c c o n d u c t i v i t i e s higher than those found f o r copper could not be confirmed, graphite-AsF^ compounds are the most h i g h l y conducting GICs studied so f a r . N o t i c e a b l y lower b a s a l plane c o n d u c t i v i t i e s are observed f o r stage 1 graphite hexa-_p -i . 28b,174 ,177 . n , . , T T T , fluor o a r s e n a t e s ' m p a r t i c u l a r where A s ( I I I ) o x i d a t i o n with has p o s s i b l y produced F i n l a t t i c e p o s i t i o n s However higher stage graphite hexafluoroarsenates are again r a t h e r h i g h l y c o n d u c t i n g 2 8 ^ ^ . Therefore a common feature i n both graphite-AsFg compounds and graphite hexafluoroarsenates seems; to be the decrease i n e l e c t r i c a l c o n d u c t i v i t y when the i o n i c content of the m a t e r i a l r i s e s above an optimum value, which corresponds to that of a m a t e r i a l of stage index 2-3. A 17 4 greater charge l o c a l i z a t i o n or the formation of covalent 112 C c\) C-F bonds i n these m a t e r i a l s have been c i t e d as the p r i n c i p a l reasons f o r t h i s f e a t u r e . One of the primary o b j e c t i v e s of t h i s work i s to explore new s y n t h e t i c routes to h i g h l y conducting GICs with graphite f l u o r o s u l f a t e as a convenient s t a r t i n g m a t e r i a l . The stage 1 graphite f l u o r o s u l f a t e best described as C^SOgF , undergoes complete i n t e r c a l a t e exchange i n SbFg and HSOgCF^. The r e a c t i o n of AsFg with. 'C^SO^F i s however not expected to r e s u l t i n a complete 'replacement. A precedent f o r t h i s 203 r e a c t i o n may be seen i n the r e a c t i o n of AsF,- with c h l o r y l 5 18.2 f l u o r o s u l f ate,' C102SO'3F C10 2S0 3F + AsF 5 • C10 2 + [ A s F 5 ( S 0 3 F ) ] (.5.9) In a d d i t i o n the [AsF,-(S0 3F) ] ion formed by the r e a c t i o n of SO 3 F ( s o l v ) and AsF^(g) at low temperatures has subsequently 19 been i d e n t i f i e d m a s o l u t i o n of l i q u i d S0 2 by F NMR spectros-18 3 copy . Due to the increased s i z e of t h i s ion compared to S0 oF and AsF r , i t i s q u i t e c e r t a i n that t h i s ion i f i n t e r c a l a t e d would r e s u l t i n an increased value f o r the carbon to anion r a t i o i n the f i r s t stage GIC. Therefore charge l o c a l i z a t i o n e f f e c t s would not be expected i n t h i s system and the p r e v i o u s l y mentioned high e l e c t r i c a l c o n d u c t i v i t i e s of graphite-AsFj- compounds provides a good i n c e n t i v e f o r the synthesis of a system c o n t a i n i n g the species [AsF^(SOgF)] . V.B.2. SYNTHETIC REACTION In a t y p i c a l p r e p a r a t i o n 0.3380 g of C^ 2 S 0 3 F , synthesized from SP 1 graphite and S 20gF 2 i n a manner described p r e v i o u s l y , were t r a n s f e r r e d i n t o a monel metal r e a c t o r i n the dry box. A f t e r evacuating the r e a c t o r , AsF,- was t r a n s f e r r e d i n vacuo, wi t h the r e a c t o r at -19 0°C. The amount of AsF c was monitored by pressure changes i n the system. The a d d i t i o n of AsF<- was terminated when a pressure of approximately 5 atm i n s i d e the r e a c t o r at room temperature had been reached. The r e a c t o r was allowed to warm up to room temperature and to 204 stand f o r 4 8 hours. This r e a c t i o n mixture was subjected to o c c a s i o n a l shaking to ensure th a t the s o l i d p a r t i c l e s were exposed to AsF,-. V o l a t i l e products were removed i n vacuo wit h the r e a c t o r at -50°C, c o l l e c t e d and analyzed by IR spectroscopy. The product was a dark blue, extremely moisture s e n s i t i v e m a t e r i a l and could be stored i n a dry atmosphere without n o t i c e a b l e d e i n t e r c a l a t i o n . M i c r o a n a l y s i s : C As S F Cal c u l a t e d f o r C, ., o A s F r S 0 o F [%] 38.80 17.05 7.29 25.94 ±M- . I b o Found [%'] 3 9 . 30 17.29 7.47 26.14 Ratios (found): As : S : F 1 : 1.01 : 5.96 V.B.3. RESULTS AND DISCUSSION (a) SYNTHESIS AND GENERAL DISCUSSION The s t a r t i n g m a t e r i a l f o r t h i s r e a c t i o n C^SO^F i s a stage 1 GIC wi t h the carbon layers o x i d i z e d to an extent where f u r t h e r o x i d a t i o n should be extremely d i f f i c u l t . Also the l a c k of space i n the g a l l e r i e s of t h i s m a t e r i a l to accomodate any other i n t e r c a l a t e s r e q u i r e s the e x t r u s i o n of SO^F i o n during the r e a c t i o n i f AsF,. molecules were t o i n t e r c a l a t e . This p a r t i c u l a r r e a c t i o n seems to proceed w i t h p a r t i a l 205 e x t r u s i o n of SOgF accompanied by the i n t e r c a l a t i o n of AsF,- to form the anion [AsFgCSO^F)] i n the i n t e r c a l a t e l a y e r s . The approximate equation given i n (5.10) i s suggested f o r t h i s 18 2 r e a c t i o n i n analogy to the p r e v i o u s l y reported r e a c t i o n of AsF 5 with C10 2S0 3F. 4C„S0oF + 2AsF c • • 2C, 1 1 [ A s F c ( S 0 o F ) ] + S o 0 c F o 7 3 o 14 5 3 2 6 2 (.5.10) The r e a c t i o n of AsF,- with CySO^F should be performed i n a metal r e a c t o r , w i t h AsF^ p u r i f i e d by trap to trap d i s t i l l a t i o n and contact w i t h glass should be avoided. The metal r e a c t o r d r i e d and conditioned p r i o r to use permitted the safe handling of AsF,- at pressures of about 5 atmospheres. I n i t i a l attempts i n Pyrex vessels s i m i l a r t o the ones used f o r s o l v o l y s i s of CySOgF by HSOgCFg had r e s u l t e d i n impure products. When a glass r e a c t o r i s used, the r e a c t i o n has to be c a r r i e d out wit h a lower pressure of AsF^ which n e c e s s i t a t e s longer r e a c t i o n time. A r s e n i c p e n t a f l u o r i d e reacts with the Pyrex v e s s e l to form S i F ^ . The presence of S i F ^ i n v o l a t i l e products was . . 19 confirmed by IR spectroscopy. In a d d i t i o n the F NMR spectrum of the product obtained i n the glass v e s s e l r e a c t i o n showed an a d d i t i o n a l s i g n a l at -176 ppm r e l a t i v e to CFCl^. 184 Assignment of t h i s resonance to S i F ^ i s based on a precedent where a peak i n the same p o s i t i o n has been observed f o r S i F ^ present as an impurity i n C * P F 6 sxCH 3N0 2 prepared i n a glass 18 5 r e a c t o r . There has a l s o been a report of a GIC of the 206 composition C2 1 +SiFj- and we conclude that S i F ^ may be i n t e r -c a l a t e d as w e l l as r e s u l t i n g i n an impure product. S t i l l micro-a n a l y s i s showed As:S r a t i o to be 1.0 i n t h i s product, showing that the extent of replacement of the SO^F ions by AsF^ was the same as i n the r e a c t i o n c a r r i e d out i n the metal r e a c t o r . Thermal decomposition on the compound [AsF^(SO^F)] showed i t s very l i m i t e d thermal s t a b i l i t y . This compound s t a r t e d decomposing i n i t i a l l y i n vacuo at approximately 40°C and the gaseous product emitted was i d e n t i f i e d as AsF,- by i t s 18 6 IR spectrum . When the temperature was r a i s e d to 60-70°C 9 8 d e i n t e r c a l a t i o n of S0 oF m the form of S o 0 r F o was i n d i c a t e d 3 2 b z by the IR spectrum. No evidence of AsF g was i n d i c a t e d i n t h i s spectrum. I n i t i a l r e l e a s e of AsF<- and a s i m i l a r l i m i t e d 18 2 thermal s t a b i l i t y have been reported f o r C10o[AsF-r(S0„F)] . z b 3 The thermal i n s t a b i l i t y of ^ [AsF (SO F)•] as w e l l as i t s high s e n s i t i v i t y towards moisture adversely a f f e c t the micro-a n a l y s i s f o r carbon. During sample manipulation and weighing p r i o r to combustion s l i g h t fuming and weight l o s s were detected. Subsequently the percentage of carbon determined was s l i g h t l y higher than expected from gravimetry which i s r a t h e r unusual f o r f l u o r i n e c o n t a i n i n g GICs, where the determined value i s often lower due to l o s s of carbon as CF^ during combustion. I t appears that the p a r t i a l decomposition of C^IAsF,- (SO^F) ] during m i c r o a n a l y s i s i s promoted by the contamination of the sample by moisture during m i c r o a n a l y s i s , r e s u l t i n g i n e r r o r -neously high carbon values. An i n d i r e c t e s t i m a t i o n of the carbon contents of t h i s sample could be made, from the 207 a n a l y t i c a l data obtained f o r As, S and F on the same sample. The percentage of AsFj-CSO^F) present i n the sample i s deduced to be 61.98% and the remainder, 38.02%, could be assumed to be carbon. This would suggest a composition of ^ [AsF,-( SO^F) ] and t h e r e f o r e an approximate composition of C^^[AsF^(SO^F)] i s used throughout t h i s d i s c u s s i o n f o r convenience. (b) STRUCTURAL AND SPECTROSCOPIC PROPERTIES The f i r s t stage nature of C^^[AsFgCSO^F)] i s i n d i c a t e d by X-ray powder d i f f r a c t i o n p a t t e r n and the E2g2 v i b r a t i o n a l mode observed i n i t s Raman spectrum. The c-axis l a y e r repeat o distance I of 7.92 i 0.03 A was deduced from the ( 002.) c r e f l e c t i o n s i n the X-ray d i f f r a c t i o n p a t t e r n where the (002) r e f l e c t i o n was observed w i t h the maximum i n t e n s i t y . The Raman spectrum d i d not show any bands a t t r i b u t a b l e to the i n t e r c a l a t e , only the E„ 0 v i b r a t i o n a l band was observed at 2g2 163 6 cm 1 . The sandwich thickness has s l i g h t l y increased o from 7.81 A f o r C^SO^F upon r e a c t i o n with AsF,-, but f a l l s ° 61 6 3 below a value of 8.10 A reported f o r C gAsF 5 and C gAsFg However the observed value of 7.92 A f o r [AsF b(SOgF)] i n d i c a t e s the nature of packing along the c-axis d i r e c t i o n . The t r i g o n a l bipyramidal s t r u c t u r e of AsF^ has been determin-. 187 ° ed to have three e q u a t o r i a l As-F bonds of 1.656 A and two o a x i a l bonds of 1.711 A. The As-F bond lengths i n AsF 3 and AsF " o 187 o18 8 b have been, reported as 1.706 it" and 1 . 850 A •respective-l y . By using these data together with the Van der Waal's r a d i u s 1 8 9 of a F atom of 1.35 A, the f o l l o w i n g s t r u c t u r a l 208 c h a r a c t e r i s t i c s can be recognized: ( i ) For the GICs, C gAsFg and C gAsFg, the thickness of the i n t e r c a l a t e l a y e r i s determined by the AsFg ion since i t has the longest As-F bond among the A s ( I I I ) 6 3 and As(V-) f l u o r i d e s . Although the As-F bonds of the AsFg molecule are shorter than that of AsFg , the former seems to determine the i n t e r c a l a t e l a y e r thickness i n the compound C^^[AsFg(SO gF)]. An o r i e n t a t i o n of the AsF r molecules w i t h t h e i r a x i a l As-F bonds perpendi-5 c u l a r to the b a s a l planes of graphite could provide an o i n t e r c a l a t e l a y e r thickness of 6.12 A, while the arrangement w i t h the a x i a l bonds p a r a l l e l to the b a s a l o planes would correspond to a l a y e r t h i c k n e s s of 4.51 A. Even the l a t t e r value i s s l i g h t l y larg.er than the d i a -o _ meter 4.45 A of the S.OgF i o n ; c o n f e r r i n g upon AsFg the dominant r o l e i n determining the thickness of the i n t e r -c a l a t e l a y e r i n C 1 1 +[AsFg ( S0 g F) ] . ( i i ) The i n t e r c a l a t e d l a y e r t h i c k n e s s c a l c u l a t e d as above f o r each of the extreme o r i e n t a t i o n s of the a x i a l As-F o bonds, together w i t h the t h i c k n e s s 3.35 A f o r the bound.- * i n g carbon l a y e r s , i n d i c a t e a sandwich t h i c k n e s s i n the range of 9.47-7.86 A. The observed I value of 7.92 A to c f o r C-j^ [ AsFg (SO gF) ] i s very close to the lowest p o s s i b l e value. The small d i f f e r e n c e may be caused e i t h e r by a t i l t e d o r i e n t a t i o n of the A s F r t r i g o n a l bipyramid as 209 77 reported e a r l i e r f o r C^gAsFg, ° r r e , 3 u c e d Coulombic a t t r a c t i o n between graphite and i n t e r c a l a t e l a y e r s i n volved i n C.^ [ AsFg (SOg F) ] as opposed to CgAsFg . Further evidence f o r assuming [A.sFg(SO^F) ] to be a new unique GIC r a t h e r than a mixture of CgAsFg and CySOgF can be gathered by co n s i d e r i n g the f o l l o w i n g observations: ( i ) The products of the r e a c t i o n of excess AsFg with CySOgF under d i f f e r e n t pressures and r e a c t i o n times on micro-a n a l y s i s i n d i c a t e d the r a t i o of As:S to be 1.0. This f i n d i n g argues against a gradual replacement of a l l SOgF by AsFg which would u l t i m a t e l y produce CgAsFg. I f the r e a c t i o n was not complete at the As:S r a t i o of 1.0, d i f f e r e n t preparations would have shown d i f f e r e n t r a t i o s depending on the r e a c t i o n c o n d i t i o n s . ( i i ) I f the f i n a l product i s a 1:1 mixture of CySOgF and CgAsFg, then the average composition should have been close to C 1 5[AsFg(SOgF)]. ( i i i ) The 1 9 F NMR spectrum of C 1 4[AsFg(SOgF)] i s i n c o n s i s t e n t with the presence of a mere mixture of CySOgF and C 0AsF c- The chemical s h i f t data obtained f o r t h i s o o m a t e r i a l together w i t h r e l e v a n t l i t e r a t u r e data are summarized i n Table (5.3). 210 TABLE. 5.3 19 F NMR DATA FOR C 1 4[AsFgCSOgF)] AND RELATED COMPOUNDS CD Compound C 1 L +S0 3F Chemical s h i f t (ppm) S(As-F) 6(S-F) 14.8 Reference This work ( i i ) C„AsFt •49.0 6 2 ( i i i ) C 1 0 o [ A s F c ( S 0 o F ) ] -49.1 40T3 z o o ( i v ) C 1 1 +[AsF 5(S0 3-F) ] -54.0 .4.0 190 This work 1 Q The F NMR spectrum of [AsT b(S03F)] shows two s i n g l e , w e l l separated resonances. An i n t e n s e , sharp s i g n a l at -54.0 ppm i s a t t r i b u t e d to the AsF,. group while a weaker s i g n a l at +4.0 ppm appears to be due to F i n a SOgF group. The s i g n a l due to AsF^ i s s h i f t e d only moderately u p f i e l d 190 r e l a t i v e to the corresponding high r e s o l u t i o n values Expected f i n e s t r u c t u r e due to f l u o r i n e - f l u o r i n e c o u p l i n g i n the AsFg group i s apparently unresolved i n the s o l i d s t a t e spectrum. S i m i l a r l y no resolved f i n e s t r u c t u r e f o r the AsFg group i s reported f o r s o l u t i o n s of CIO2[AsFgCSO^F)] 190 HS0 3F at 25°C ,183 however the anion lAsFr(S0„F)] has been 0 o reported to show two m u l t i p l e t s at -47.5 and -69.6 ppm r e s p e c t i v e l y i n l i q u i d SO2 at -70°C. The resonance due to the SOgF group i n [AsF^CSOgF)] i s s h i f t e d s t r o n g l y u p f i e l d , r e l a t i v e to the corresponding resonance i n the high r e s o l u t i o n spectrum of C102.[AsF5 (SO^F) ] 211 19 0 d i s s o l v e d i n HSQgF . As described i n Chapter I I I , graphite f l u o r o s u l f a t e s , C S0„F, with n ranging from 7-12, e x h i b i t a 1*1 O s i n g l e resonance i n the range of 10-15 ppm depending on the value of n. Therefore the resonance observed f o r C-^ [AsFg(SOgF)] at 4.0 ppm i s s i g n i f i c a n t l y d i f f e r e n t from those of graphite f l u o r o s u l f a t e s . There seems to be a s i g n i f i c a n t d i f f e r e n c e i n the nature of bonding between AsFg and SOgF i n the i n t e r c a l a t e d [AsFg(SOgF)] i o n , and the same i o n i n s o l u t i o n . The Raman bands of the SOgF group i n s o l i d C10 2lAsFg(SOgF)] 190 have i n d i c a t e d that the AsFg molecules might be weakly + - . . . bridged between ClO^ and SOgF with p o s s i b l e c a tion~anion i n t e r a c t i o n between these i o n s . However i n C.^ [AsFg (SOgF) ] the macro c a t i o n C-^ i n t e r a c t s d i r e c t l y with the anion [AsFg(SOgF)1 . I t seems a d i s t i n c t , a l b e i t t h ermally l a b i l e , anion i s present i n the i n t e r c a l a t i o n compound C ^ [AsFg( SOgF] . Due to the greater charge d e l o c a l i z a t i o n i n the anion [AsFg(SOgF)] compared to SOgF , reduced anion r e p u l s i o n and t i g h t e r packing compared to CySOgF are observed i n the i n t e r -c a l a t e l a y e r s of t h i s compound. In contrast to the d i r e c t i n t e r c a l a t i o n of AsFg, the r e a c t i o n of AsFg w i t h CySOgF to give. .C^ [AsFg ( SOgF) 1 ~ represents an o v e r a l l r e d u c t i o n of graphite r a t h e r than o x i d a t i o n . Therefore the formation of AsFg and AsF^ - are n e i t h e r expected nor observed during t h i s r e a c t i o n . 212 V.C REACTIONS OF C DAsF c and C, 0AsF c WITH S o 0 c F o o b 1 2 b 2 6 2 V.C.I INTRODUCTION The f i r s t stage i n t e r c a l a t i o n compound, CgAsFg, prepared by the i n t e r c a l a t i o n of AsFg i n t o graphite i s now g e n e r a l l y accepted to contain AsFg, AsF,. and AsFg i n the g a l l e r i e s . The 6 3 e q u i l i b r i u m : 3AsF c + 2e 2AsF e" + AsF„ (5.3) o b 3 has been proposed by B a r t l e t t to account f o r the presence of these i n t e r c a l a t e s , but the p r e c i s e p o s i t i o n of the e q u i l i b r i u m and hence the i o n i c content of t h i s m a t e r i a l i s s t i l l u n c e r t a i n . The i n t e r c a l a t i o n compound CgAsFg i s r e p o r t e d l y not s t a b l e i n a dynamic vacuum at room temperature as i t slowly looses AsF_. o Subsequent a d d i t i o n of AsF,- and continuous c y c l i c pumping w i l l 171 172 ev e n t u a l l y r e s u l t i n the formation of C-^AsFg according to ' : 3C0AsF.. ^—^ 2C, 0AsF c + AsF„ (5.12) o b N 12 b 3 A l t e r n a t e attempts t o f u r t h e r increase the i o n i c content of CgAsFg by r e a c t i n g i t w i t h elemental f l u o r i n e to o x i d i z e AsFg had seemingly r e s u l t e d i n the formation of covalent C-F bonds 1 1 2 3'. Bis (f l u o r o s u l f u r y l ) peroxide , ; S20gF 2 , being a weaker o x i d i z i n g agent than f l u o r i n e should be more s e l e c t i v e i n o x i d i z i n g AsFg in•accordance w i t h published 213 191 precedents , while avoiding side r e a c t i o n s . At the outset the f o l l o w i n g r e a c t i v i t i e s ' i n v o l v i n g the major e q u i l i b r i u m species were a n t i c i p a t e d : ( i ) I n t e r c a l a t e d A s F ' ions would not be r e a c t i v e towards b S 2 0 6 F 2 . ( i i ) A r s e n i c p e n t a f l u o r i d e , AsF^, should form AsFj-(SOgF) or be replaced from the g a l l e r i e s during t h i s r e a c t i o n by SOgF -. ( i i i ) I n t e r c a l a t e d AsF„ would r e a c t with S o 0 r F o according to o 2 b 2 equation (5.13) forming the seemingly viscous l i q u i d AsFg(SOgF) which could p o s s i b l y be removed In a dynamic vacuum. As F Q + S o 0 c F o • A s F o ( S 0 o F ) o (5.13) o 2 b 2 6 i I C i v ) B i s ( f l u o r o s u l f u r y l ) peroxide, S 2 0 g F 2 , may a l s o o x i d i z e graphite f u r t h e r . To confirm the f i r s t assumption, the. i n e r t n e s s of AsF towards S 2 0 g F 2 , the f i r s t step of t h i s study was d i r e c t e d towards the i n v e s t i g a t i o n of the r e a c t i o n of C-^AsFg with excess S„0_F o. The r e a c t i o n of C 0AsF c with S o 0 r F o was then 2 6 2 8 b z b z attempted as an a d d i t i o n a l step towards understanding the nature of graphite-AsFj- compounds. Therefore the s t u d i e s described i n t h i s s e c t i o n may be viewed as an e x p l o r a t o r y 214 attempt to t a c k l e the complex e q u i l i b r i u m i n CgAsFg by chemical means. V.C.2. SYNTHETIC REACTIONS' (a) REACTION OF C, 0AsF r. WITH S„Crl'0 1Z 6 2 b 2 In a t y p i c a l r e a c t i o n 0.2635 g of CgAsFg prepared 61 according to the method described i n the l i t e r a t u r e was evacuated f o r s e v e r a l hours and reacted w i t h excess AsFg. A f t e r removing the excess AsFg i n vacuo t h i s sample was evacua-ted f o r s e v e r a l hours u n t i l I t s weight remained constant at 0.2198 g. The composition of t h i s sample was determined as ' " l l 8^ s F6 ky mi c r o a n a l y s i s (%C = 42.69) and gravimetry. To 0.1727 g of C-i q 0AsF~, an excess of S o 0 c F o was added and 11. o b.. Z o Z allowed to react f o r 48 hours at room temperature. A f t e r removing the v o l a t i l e s i n vacuo the product was exposed to a dynamic vacuum. A blue-black product (.0.1831 g) was obtained when the sample reached constant weight. M i c r o a n a l y s i s : C Ca l c u l a t e d f o r Ciy gAsFg [%] 42.8 0 Found (before r e a c t i n g with S 2'O gF 2) [%] 42.69 Found ( a f t e r r e a c t i n g with 'S2'06F2) I%] 37.7.1 215 (b) . REACTION. OF C0As.F WITH S o0 eF_ o o 2 b 2 In a t y p i c a l r e a c t i o n 0.5130 g of SP 1 graphite powder was reacted w i t h excess AsF,- (^ 5 atm) i n a monel metal r e a c t o r o 61 f o r 7 days as described i n the l i t e r a t u r e . A f t e r removing the excess AsF^ at -50°C, a dark blue product was obtained and 19 c h a r a c t e r i z e d by F NMR and X-ray d i f f r a c t i o n as CgAsF,.. 0.8279 g of t h i s compound was t r a n s f e r r e d i n t o another r e a c t o r i n the dry box and excess S„0_Fo (^10 ml) was d i s t i l l e d onto 2 b 2 i t at -198°C. The r e a c t i o n mixture was allowed to stand at room temperature f o r 3 8 hours. The v o l a t i l e products were analyzed by IR spectroscopy and removed i n vacuo. The product was exposed to a dynamic vacuum and a black powder of 0.8265 g weight was obtained when the sample reached a constant weight. M i c r o a n a l y s i s : ( i ) C a l c u l a t e d f o r C 1 Q A s F 5 [%] 41.30 Found [%] 41.41 NOTE: The product CgAsF,- has been reported to reach a composition of C^AsF,- when exposed to dry N 2• ( i i ) C As S F Calc u l a t e d f o r C±2 AsF C.SOgF) .'[;%] 36.94 18.90 8 . 07 23.9.7 Found [%] 3 7.71 18.85 8.10 24.25 Ratios (Found) As : S : F "= 1 : 0 . 9 9 6 : 5 . 0 7 3 V.C.3. • RESULTS AND DISCUSSION (a) . REACTION OF .C,.0AsF._. WITH S o0 F . 12 b 2 b 2 An i n t e r c a l a t i o n ^ compound w i t h approximate composition of C^AsFg was synthesized by a c y c l i c process of r e a c t i n g graphite with AsF^ to form CgAsF^ and evacuating i t i n a . . . 171 172 dynamic vacuum. Although i n i t i a l studies ' i n d i c a t e the composition of the vacuum st a b l e m a t e r i a l to be C-^AsFg , a 17 3 recent report suggests C-^AsFg t o be the f i n a l composition. Our r e s u l t s , b a s e d on weight increase as w e l l as m i c r o a n a l y s i s , f o r carbon support the composition C-^AsFg. The r e a c t i o n of the m a t e r i a l C n, Q A s F r (%C = 42.80) wi t h S o 0 r F o at room 1 1 . 8 6 2 b 2 temperature produced a vacuum s t a b l e product (%C = 37.71) which was i d e n t i f i e d as a stage 1 m a t e r i a l .(I = 7.75 if & c o 0.03 A) by X-ray powder d i f f r a c t i o n . The decrease i n carbon contents i n the product and the small weight increase i n d i c a t e f u r t h e r o x i d a t i o n by l i q u i d S 20gF 2. However, i d e n t i f i c a t i o n of the f i n a l product was found to be d i f f i c u l t due to l a c k 19 of infor m a t i o n on the nature of the i n t e r c a l a t e s . The F NMR of t h i s sample showed only a s i n g l e peak at -54 ppm which was a t t r i b u t e d to an As-F resonance. The absence, of any s i g n a l s i n the S-F region, precluded the i d e n t i f i c a t i o n of t h i s m a t e r i a l . Although the f u r t h e r o x i d a t i o n of carbon l a y e r s i s evident, f u r t h e r d e t a i l e d s t u d i e s are required to obtain a complete understanding of t h i s r e a c t i o n . 217 (b) . .REACTION. GF C 0AsF c WITH. S.o0. F • o 5 2 b 2 The r e a c t i o n of C QAsF r w i t h S n0 F_ a l s o seems to be more o h 2 6 2 complicated than expected r e s u l t i n g i n a f i r s t stage compound f o r which chemical a n a l y s i s i n d i c a t e s As : S : F r a t i o s to be 1 : 0.996 : 5.073 suggesting a stoichiometry of AsF^CSO^F) f o r the i n t e r c a l a t e . No evidence f o r C-F bond formation during 19 t h i s r e a c t i o n was observed m the F NMR of the f i n a l 19 product. The F NMR spectrum confirmed the presence of f l u o r i n e i n two d i f f e r e n t environments, with s i g n a l at -53.2 ppm (As-F) and +9.9 ppm (S-F) r e s p e c t i v e l y . While the As-F resonance of t h i s m a t e r i a l i s almost i n the same p o s i t i o n as observed e a r l i e r (see Table 5.3) f o r C-, „ [ AsF c (S0 oF) ] , the 14 o o peaks due to S-F resonance i n both compounds are separated by about 5.9 ppm. The chemical s h i f t 9.0 ppm of S-F resonance of the m a t e r i a l formed by r e a c t i n g CgAsFg wi t h S^O^F^ i s i n the same region where i n t e r c a l a t e d SO^F ions are u s u a l l y observed. M i c r o a n a l y s i s r e s u l t s on t h i s compound are a l s o i n accord f o r the existence of SO^F ions i n the g a l l e r i e s . However, as i n the previous r e a c t i o n , here, a complete i d e n t i f i c a t i o n of the i n t e r c a l a t e s i s at present not p o s s i b l e . The r e s u l t s of m i c r o a n a l y s i s w i t h As : S : F r a t i o s of 1 : 0.9973 : 5.073, suggest the presence of As(V) and A s ( I I I ) f l u o r i d e s assuming that some, o x i d a t i o n of carbon l a y e r s and hence some anion formation (AsFg 5 AsFgCSO^F) or SO^F ) has taken p l a c e . But an estimation of the amount of As(V) and 218 As ( I I I ) species, i s not p o s s i b l e from the a v a i l a b l e data. The 19 use of F NMR to c h a r a c t e r i z e graphite-AsFg compounds has always been l i m i t e d ; the i n a b i l i t y to detect the i n t e r c a l a t e d 19 5 9 AsFg m CgAsFg by F NMR spectroscopy i s already known and the same l i m i t a t i o n seems to p r e v a i l i n the a n a l y s i s of the GIC formed i n the r e a c t i o n of CgAsFg with S^OgF^• Again, by analogy with the r e a c t i o n of CgAsFg , the r e s u l t s are p u z z l i n g the. system being r a t h e r - •> • complex. The r e s u l t s at t h i s p o i n t do not allow a c o n s i s t e n t i n t e r p r e t a t i o n nor a b e t t e r understanding of the graphite-AsFg system. The experiments described here should be viewed as p r e l i m i n a r y i n v e s t i g a t i o n s with f u r t h e r work r e q u i r e d before f i n a l conclusions are p o s s i b l e . V.D. CONCLUSION On one hand the s o l v o l y s i s of stage 1 graphite f l u o r o -s u l f ate, CySOgF, by SbFg r e s u l t s i n the complete replacement of a l l i n t e r c a l a t e d S0 oF ions by SbF ~, forming the graphite o b hexafluoroantimonate, CgSbFg. The r e a c t i o n of CySOgF with AsFg on the other hand r e s u l t s i n p a r t i a l e x t r u s i o n of the i n t e r c a l a t e d SOgF ion s . Complete replacement seems impossible and the r e s u l t i n g compound [AsFg (SOgF') ] i s r a t h e r s t a b l e / P r e l i m i n a r y i n v e s t i g a t i o n s on the r e a c t i v i t y of CgAsFg towards S 20gF 2 i n d i c a t e s the c a p a b i l i t y of the l a t t e r compound to f u r t h e r o x i d i z e the carbon l a y e r s i n CgAsFg without forming C-F bonds. Further work i s r e q u i r e d f o r the complete understanding of t h i s r e a c t i o n as w e l l as the r e a c t i o n of the 219 stage 1 graphite-SAsFg compound, CgAsFg, with b i s ( f l u o r o s u l f u r y l ) peroxide. 20 CHAPTER VI INTERCALATION OF HALOGEN FLUOROSULFATES INTO GRAPHITE 221 CHAPTER VI INTERCALATION OF HALOGEN FLUOROSULFATES INTO GRAPHITE VI.A. INTRODUCTION The i n t e r c a l a t i o n of halogens and interhalogens i n t o graphite have been a major area of research a c t i v i t y ever since the i n t e r c a l a t i o n of bromine was reported. Bromine, which was the f i r s t halogen to be i n t e r c a l a t e d , formed a stage 2 GIC formulated as C gBr the l i m i t i n g composition at 192 room temperature . The mechanism of the i n t e r c a l a t i o n of B r 2 has been studied i n d e t a i l and appears to be w e l l under-4 8 5 4 stood ' . The nature of the i n t e r c a l a t e , the extent of charge t r a n s f e r and the s t r u c t u r e of r e s u l t i n g GICs are f a r more c o n t r o v e r s i a l . While the g r a p h i t e - B r 2 system has occupied researchers mainly, subsequent studies on the behaviour of other halogens towards graphite have allowed the f o l l o w i n g conclusions : (I) F l u o r i n e r e a c t s with graphite to form compounds i n which the aromatic l a y e r s t r u c t u r e i s destroyed. There g are s e v e r a l s t r u c t u r a l types of graphite f l u o r i d e s . ( I i ) Chlorine incorporates i n t o graphite at temperatures as low as -57°C to form the compound C g C l which i s not st a b l e much above t h i s temperature. The reason f o r t h i s C l 2 uptake whether i t i s due to i n t e r c a l a t i o n or 222 surface adsorption i s un c e r t a i n . ( i i i ) Iodine does not i n t e r c a l a t e i n t o g r a p h i t e . The molecular s i z e , low o x i d i z i n g power and r a t h e r low vapour pressure at ^ 25°C, a l l are v a l i d reasons f o r the l a c k of r e a c t i v i t y . A number of d i - , t e t r a - and hexa- atomic interhalogens 6 1 are found to i n t e r c a l a t e as w e l l ' . A d e t a i l e d review at t h i s time w i l l not be attempted, since the s t r u c t u r e and composition of these m a t e r i a l s are ofte n c o n t r o v e r s i a l and relevance to the present study i s s l i g h t . The d i f f e r e n c e s i n behaviour of halogens and interhalogens when i n t e r c a l a t e d i n t o graphite generated our i n t e r e s t In the st u d i e s of i n t e r -c a l a t i o n of halogen ( I ) f l u o r o s u l f a t e s CXSO^F, where X = Br,. C l , I) and t h e i r d e r i v a t i v e s . Some of the p r i n c i p a l reasons which p o i n t towards some i n t e r e s t i n g behaviour of halogen ( I ) f l u o r o s u l f a t e s when i n t e r a c t e d w i t h graphite are found i n the methods adopted f o r t h e i r syntheses as w e l l as t h e i r p h y s i c a l and chemical p r o p e r t i e s . The halogen ( I ) f l u o r o s u l f a t e s , XSOgF are obtained by the r e a c t i o n of the halogen with the s t o i c h i o m e t r i c amount of S o0_F o according t o : 2 6 2 X„(l) + S o 0 c F o • 2XS0 QF (6.1) 2 2 6 2 6 Of the "parent" molecules, S 2O gF 2 o x i d a t i v e l y i n t e r c a l a t e s i n t o graphite to give stage 1 GICs with a l i m i t i n g composition 223 of CySOgF, while the halogens show d i f f e r e n c e s i n behaviour as described p r e v i o u s l y . Therefore i t seems l i k e l y that the halogen (I) f l u o r o s u l f ates of the' type '• XS Og F with' X=CT, Br. or L. w i l l vary i n t h e i r - r e a c t i v i t y towards graphite and " t h e i r a b i l i t y to i n t e r -105 c a l a t e . No previous i n t e r c a l a t i o n by any halogen oxacid seems to have been undertaken. The p h y s i c a l p r o p e r t i e s of halogen (I) f l u o r o s u l f a t e s as shown i n Table (6.1), show.that the i n t e r c a l a -t i o n process i n v o l v i n g CISOgF and.BrSOgF can be c a r r i e d out at room temperature v i a l i q u i d or gas phase r e a c t i o n s . Iodine (I) f l u o r o s u l f a t e on the other hand would have to be heated to a melt before the i n t e r c a l a t i o n i s attempted since s u i t a b l e solvents are scarce. The s t r u c t u r a l feature observed i n halogen ( I ) f l u o r o -s u l f a t e s i n d i c a t e t h e i r c a p a b i l i t y to i n t e r a c t o x i d a t i v e l y w i t h graphite. These p r o p e r t i e s have been discussed e l s e -105 where i n d e t a i l . Even though rigorous s t r u c t u r a l informat-ion, are not a v a i l a b l e f o r halogen ( I ) f l u o r o s u l f a t e s , t h e i r v i b r a t i o n a l spectra have l e d t o some important deductions. P o l a r i z e d Raman spectra suggest C symmetry f o r BrS0„F and S o CISOgF with the XOSF (where X = CI, Br) moiety i n a plane with X and F atoms i n e i t h e r c i s or trans p o s i t i o n as shown i n the f o l l o w i n g page. Besides the p h y s i c a l p r o p e r t i e s l i s t e d i n Table (6.1), 9 3 19 3 vapour de n s i t y measurements f o r CISOgF ' , molecular weight studi e s f o r BrSOgF 9 2, 1 9 F NMR11'8 and v i b r a t i o n a l data f o r XSOgF 19 4 19 5 -u (X = Br ,C1 ) a H provide evidence for" c o v a l e n t l y bound monomeric-molecules i n the gas phase with a tendency f o r TABLE 6.1: SOME PHYSICAL PROPERTIES OF SELECTED HALOGEN FLUOROSULFATES PROPERTY BrSOgF 92,105 C1S0 3F 93,105 94 IS0 3F 93,105 B r ( S 0 3 F ) 3 melting point (°C) b o i l i n g point (°C) density (g/ml) + 31. 5 +117.3 2.2 38 @ 0 25 C -84. 3 + 45.1 1.711 @ 0 20 C + 50.2 + 59.0 vapour pressure at 25°C (Torr) s t a b i l i t y and colour 19 F NMR chemical s h i f t r e l . to CFC1 (ppm) 16.98 363.1 red l i q u i d 0 yellow l i q u i d s t a b l e up to 150 C 34.6 33.9 black-brown s o l i d , stable, up to 150 °C 44. 0 pale yellow s o l i d , slowly dec-omposes at room temp. 39 . 0 225 X \ / V 0 F 0 F 0 C I S t r a n s STRUCTURAL FORMS OF HALOGEN (I) FLUOROSULFATES, XS0 3F (X = C l , Br) in t e r m o l e c u l a r a s s o c i a t i o n i n the condensed phase. These compounds may be viewed as p o l a r i z e d i n the manner X — OSO2F as i n d i c a t e d by t h e i r chemistry: capable of i o n i c d i s s o c i a t i o n i n the l i q u i d s t a t e as evidenced by e l e c t r i c a l conductance 9 2 measurements . Hence the halogen (I) f l u o r o s u l f a t e s could be regarded as "pseudo interh a l o g e n s " . Depending on the o x i d a t i v e strength,.oxidative i n t e r c a l a t i o n i s f e a s i b l e with two c o n t r a s t i n g behaviour patterns a n t i c i p a t e d : (a) molecular i n t e r c a l a t i o n as XSO^F wit h e l e c t r o n t r a n s f e r from graphite and p o s s i b l y a subsequent rearrangement; and (b) o x i d a t i v e f l u o r o s u l f o n a t i o n with X 2 ~ r e l e a s e , o f f e r i n g an a d d i t i o n a l somewhat c i r c u i t o u s route to graphite f l u o r o s u l f a t e s . 226 I f the halogen ( I ) f l u o r o s u l f a t e : molecules would e x i s t p r i m a r i l y In the molecular form i n the i n t e r c a l a t e l a y e r s i t would provide an opportunity to compare t h e i r chemical behaviour to that of fre e XSOgF molecules. Further r e a c t i o n s of such i n t e r c a l a t e d XSOgF should broaden the chemical spectrum. In cont r a s t to §2®S^2 ^ l u o r o s u l f a t e s of c h l o r i n e , bromine and iodin e are m i l d e r o x i d i z i n g agents and side r e a c t i o n s such as graphite oxide or f l u o r i d e formation are l e s s l i k e l y . VI.B. INTERCALATION OF BROMINE FLUOROSULFATES INTO GRAPHITE VI.B.1. CHEMICAL BEHAVIOUR OF BROMINE FLUOROSULFATES Two bas i c types of bromine f l u o r o s u l f a t e s , bromine (I) f l u o r o s u l f a t e , BrSOgF, and bromine ( I I I ) f l u o r o s u l f a t e Br(SOgF) are w e l l known, while BrgSOgF appears to e x i s t only at low 92 temperatures . Both s t a b l e f l u o r o s u l f a t e s can be e a s i l y synthesized and stored i n Pyrex v e s s e l s . Bromine (I) f l u o r o -s u l f a t e can be d i s t i l l e d i n vacuo at room temperature and 92 e x h i b i t s thermal s t a b i l i t y up to 150°C . Although i t s moisture s e n s i t i v i t y and r e a c t i v i t y w i t h grease cause handling problems, i t has found a p p l i c a t i o n s as a u s e f u l s y n t h e t i c reagent i n a wide range of r e a c t i o n s . Some of the r e a c t i o n s which are r e l a t e d to t h i s work are o u t l i n e d below, and 105 d e t a i l e d d e s c r i p t i o n s can be found elsewhere (I) Bromine (I ) f l u o r o s u l f a t e could be o x i d i z e d f u r t h e r by b i s ( f l u o r o s u l f u r y l ) peroxide to form bromine ( I I I ) f l u o r o s u l f a t e according to equation (6.2). 227 Br0S0 oF + S o0 F 0 >- Br(0S0oF)„ (6.2) z z b z 1 6 ( i i ) Bromine ( I I I ) f l u o r o s u l f a t e on the other hand may be reduced by an excess of Br^ t° bromine (I) f l u o r o s u l f a t according to equation (6.3). B r ( O S 0 2 F ) 3 + B r 2 *'• 3'BrOS0 2F (6.3) VI.B.2. SYNTHETIC REACTIONS (a) THE REACTION .OF. .Br.S.O.g.F WITH GRAPHITE. AT. AMBIENT TEMPERATURE In a t y p i c a l r e a c t i o n , approximately 2 0 ml of f r e s h l y prepared BrSO^F were d i s t i l l e d over 0.5237 g of vacuum d r i e d SP 1 graphite powder and the mixture was allowed to stand at room temperature under vigorous magnetic s t i r r i n g . The reddish-brown colour of the pure BrSO^F p e r s i s t e d i n the l i q u i d phase throughout the r e a c t i o n and no evidence f o r B r 2 e v o l u t i o n could be detected. Excess BrSO^F was removed i n a dynamic vacuum. Complet removal of the excess BrSO^F was achieved by monitoring the 19 evaporation process by gravimetry and the F NMR spectra of 19 the s o l i d . Samples analyzed by F NMR before complete removal of excess BrSOgF showed two s i g n a l s at 9.0 ppm and about 34 ppm r e s p e c t i v e l y , (see F i g . 6.1(a)). The l a t t e r 228 The , S F nmr spectrum of C n BrS0 3 F 6.1 (a) "c^BrSOsF" 8 = 9.0 ppm 34 ppm (b) C.jBrSOsF 8 =9.3 ppm 229 s i g n a l was broad and of low i n t e n s i t y . The strong s i g n a l w i t h the lower chemical s h i f t value p e r s i s t e d even a f t e r prolonged pumping, while the broad s i g n a l e v e n t u a l l y disappeared. F i n a l l y a vacuum s t a b l e sample showed a s i n g l e s i g n a l at 9.3 ppm as shown i n F i g . 6.1(b). This s i g n a l was a t t r i b u t e d to i n t e r c a l a t e d BrSOgF and the weak s i g n a l observed at ^34 ppm was assigned t o surface adsorbed or c a p i l l a r y condensed m a t e r i a l . The r e s u l t i n g s o l i d showed a deep blue l u s t r e . Gravimetry i n d i c a t e d s l i g h t l y v a rying compositions depending on the type of graphite used: STARTING MATERIAL (I) N a t u r a l graphite f l a k e s ( i i ) HOPG p l a t e s ( i i i ) SP 1 powder COMPOSITION OF PRODUCT C 1 2 > 1 4 B r S 0 3 F C 1 2 . 6 0 B r S O 3 F  C 1 2 . 0 3 B r S O 3 F X-ray powder d i f f r a c t i o n on the sample"of composition ^12 0 3 B r ^ 3 F s ^ o w e d i t w a s p r i m a r i l y a stage 1 GIC w i t h a o c-axis l a y e r repeat distance I* of 7.7 5 ± 0.0 3 A. Microanalyses on t h i s sample gave the f o l l o w i n g r e s u l t s : C a l c u l a t e d f o r C 1 2 B r S 0 3 F Br TOTAL [%]• 44.59 9.91 24.74 5.88 14.88 100.00 Found [%] 44.74 10.22 24.48 5.75 14.71 99.90 mole r a t i o Br : S : F 1.00 : 1.04 : 1 . 01 Oxygen content i s c a l c u l a t e d assuming the mole r a t i o Br : 0 to be 1 : 3. 230 Higher stage GICs c o n t a i n i n g BrSO^F were prepared by gas phase i n t e r c a l a t i o n w i t h HOPG as the s t a r t i n g m a t e r i a l . These samples were used f o r e l e c t r i c a l c o n d u c t i v i t y measurements and d e t a i l s of the method adopted f o r sample prepa r a t i o n as w e l l as the composition of the products are described i n Chapter V I I . (b) THE REACTION. OF BrSO^.F WITH GRAPHITE AT 10.5.°.C. TO 110° C In a t y p i c a l r e a c t i o n 0.1776 g of SP 1 graphite powder was heated to 105-110°C together with about 2 0 ml of f r e s h l y d i s t i l l e d BrSO^F, f o r a per i o d of about 48 hours. Bromine released during the r e a c t i o n was evident due to I t s colour i n the vapour over the r e a c t i o n mixture and the dark brown colour of the excess l i q u i d remaining. V o l a t i l e m a t e r i a l s were removed i n a dynamic vacuum and a black-blue s o l i d of 0.403 8 g was obtained when the sample reached constant weight. X-ray powder d i f f r a c t i o n on t h i s sample showed i t to be of stage 1 o composition with c-axis l a y e r repeat distance of 7.7 6 ± 0.03 A. Microanalyses of t h i s sample gave the f o l l o w i n g r e s u l t s : C Br S F 0 TOTAL Ca l c u l a t e d f o r C 2 Q B r F ( S 0 3 F ) 2 f%] 44.77 14.87 11.93 10.61 17.88 100.00 I%] 44.50 14.90 12.08 10.55 17.90* 99.93 Mole r a t i o B r : S : F = 1.00:2.02:2.98 Oxygen content i s c a l c u l a t e d assuming the mole r a t i o Br : 0 to be 1 : 6. 231 The "V nmr spectrum of C 2 0 BrF(S0 s F) 2 C 2 0 B r F ( S 0 3 F ) 2 • 8 s 9.7 ppm 8=-84.1 ppm ) \ 232 (c) THE REACTION OF Cn -BrSO-F WITH S-.0-.F. ± Z 5 Z D / In a t y p i c a l r e a c t i o n 0.2785 g of SP 1 graphite powder was reacted w i t h BrSOgF at room temperature to form C-^BrSO-F as described i n s e c t i o n (b). The composition of the product was determined g r a v i m e t r i c a l l y . An excess of S-0gF- (about 10 ml) was d i s t i l l e d over t h i s sample and the suspension was magnetically s t i r r e d f o r 48 hours at room temperature. Excess S.OgF- was subsequently removed i n vacuo and the remaining v o l a t i l e products were removed i n a dynamic vacuum over a period of s e v e r a l days. A black powdery m a t e r i a l of 0.82 91 g was i s o l a t e d . Gravimetry suggested a composition of C^j- gBr(SO-F)- and mi c r o a n a l y s i s agreed w e l l w i t h the composition of C^g gBr(S0_F)g. C Br F F/ Br Cal c u l a t e d f o r C,- r B r ( S 0 - F ) . [%] 34.43 13.91 9.91 3.00 lb.o o o Found [%] 34.48 14.04 10.01 3.00 X-ray powder d i f f r a c t i o n i n d i c a t e d t h i s sample to be p r i m a r i l y of stage 1 composition w i t h c-axis l a y e r repeat distance I of 7.92 ± 0.03 A. (d) . THE REACTION. OF CySOgF. WITH BrSOgF In a t y p i c a l r e a c t i o n 0.3045 g of CySOgF, prepared from the r e a c t i o n of SP 1 graphite powder wi t h an excess of S-O-F- were suspended i n an excess of BrSO-F f o r 48 hours at z b z o room temperature under magnetic s t i r r i n g . The excess of 233 The l 9 F nmr spectrum of the Product of the Reaction of CfcBrSOjF with S 2 0 6 F 2 . C l 2 BrSQ 3 F+ S 2 0 6 F g S = IO ppm 234 BrSOgF was removed i n a dynamic vacuum. Samples were analyzed 19 by F NMR a f t e r various times of exposure to the vacuum. At the i n i t i a l stages of evaporation the samples showed two broad resonances at 11 and 32 ppm r e s p e c t i v e l y (see F i g . 6.4), but continued pumping produced a sample which showed only one resonance at 10.1 ppm. This product was found to be of stage 1 composition with c-axis l a y e r repeat distance I of o 7.86 ± 0.03 A. M i c r o a n a l y s i s on t h i s sample showed the percen-tage contents of carbon and bromine to be 45.45 and 1.88 r e s p e c t i v e l y . (e) THE REACTION OF CgBr WITH BrSOgF In the f i r s t step of t h i s r e a c t i o n 0.183 8 g of SP 1 graphite powder were reacted w i t h excess Br^ l i q u i d at room temperature f o r ^ 5 hours. The excess Bv^ was removed i n vacuo and a product of approximate composition C^  gBr (by gravimetry) was obtained. This sample was reacted w i t h an excess of BrSOgF at room temperature w i t h magnetic s t i r r i n g . The l i q u i d phase subsequently turned brown i n d i c a t i n g the e x t r u s i o n of bromine from the i n t e r c a l a t i o n compound. The remaining l i q u i d was removed i n a dynamic vacuum and 0.42 2 4 g of a blue-black product was obtained. The weight change observed i n d i c a t e d the i n t e r c a l a t i o n of BrSOgF to a composition of 19 C,n oBrS0_F. The F NMR of t h i s sample showed a s i g n a l at I I . o 3 9.5 ppm confirming the i n t e r c a l a t i o n , of BrSOgF. (Cl) C i SO/ *BrSO,F 8-11.03 S * * 3 2 2 2 ^2$ 61 201 401 607 otter short pumping - 4 0 (J 43 80 120 «• THE REACTION OF CgSO.F WITH BrSOgF AS OBSERVED BY 1 9 F NMR SPECTROSCOPY 236 M i c r o a n a l y s i s : C Ca l c u l a t e d f o r C 1 2 B r S 0 3 F [%] 44.59 Found [%] 44.5 0 VI.B.3. REACTION OF GRAPHITE BROMINE FLUOROSULFATES (a) . REACTION OF C^BrSO^F ;WITH HSOgCFg As described i n s e c t i o n V L B . (2 ), 0.2749 g of SP 1 graphite were converted to 0.6166 g of C 1 2 B r S 0 3 F . An excess ( 10 ml) of f r e s h l y d i s t i l l e d HS0 3CF 3 was d i s t i l l e d over t h i s sample and the suspension was s t i r r e d m agnetically f o r 48 hours at room temperature. E v o l u t i o n of B r 2 was evident from i t s colour i n the a c i d and the vapour over the r e a c t i o n mixture. A f t e r removing the v o l a t i l e products i n vacuo 0.5 87 3 g of a blue-black bromine fr e e product was obtained. 19 The X-ray d i f f r a c t i o n and F NMR r e s u l t s f o r t h i s sample were i d e n t i c a l to the r e s u l t s obtained f o r the compound C 1 2 S 0 3 C F 3 . Mi c r o a n a l y s i s C C a l c u l a t e d f o r C 1 2 S 0 3 C F 3 [%] 51.01 Found [%] 51.24 237 (b) REACTION. OF Q 2BrSOgF WITH Br-This r e a c t i o n was attempted by a l l o w i n g 0.56 99 g of C-^-BrSO F J prepared according t o s e c t i o n V L B (2) to stand i n 3 an excess of Br- l i q u i d at room temperature f o r 2 days. The excess Br- was c a r e f u l l y removed i n vacuo while c o o l i n g the sample to prevent r a p i d d e i n t e r c a l a t i o n . A black f l a k y s o l i d 19 was obtained and the F NMR of t h i s sample showed a s i g n a l at 9.7 ppm. Raman spectra of t h i s sample showed the E_ - band z g z at (1645-1647) cm 1 and an a d d i t i o n a l band of medium i n t e n s i t y at 240 cm L But t h i s sample was observed to be thermally unstable at room temperature, slowly decomposing w i t h the l i b e r a t i o n of Br-. When exposed to a dynamic vacuum, t h i s sample l o s t weight r a p i d l y and the f i n a l product showed only the E- - band i n the Raman spectrum. The absence of the band 2g2 at 2 40 cm 1 showed that i t could be a t t r i b u t e d to i n t e r c a l a t e d Br. present i n the sample before evacuation. Weight changes i n various preparations i n d i c a t e d that the f i n a l product was lower i n weight than the C-^-BrSOgF used as s t a r t i n g m a t e r i a l . (A t y p i c a l weight l o s s of 82 mg was observed f o r 57 0 mg of C 1 2 B r S 0 3 F ) . Cc) THE REACTION. OF. C- -Br.(.S.O.-.F.)... WITH Br-io 3 3 I In a t y p i c a l r e a c t i o n 0.155 0 g of SP 1 graphite powder were q u a n t i t a t i v e l y converted to C 1 2BrS0-F and then to C-_Br(S0„F)o as described i n s e c t i o n V L B (2). Excess Br-io 3 3 i was d i s t i l l e d onto t h i s sample and the mixture magnetically s t i r r e d at room temperature f o r 2 4 hours. The v o l a t i l e 238 products were removed i n vacuo and the sample exposed to a dynamic vacuum u n t i l a .product of constant weight was obtained. The f i n a l product weighed 0.34 81 g and had the blue l u s t r e e a r l i e r observed i n C-^BrSOgF. Gravimetry suggested a composition of C^^ ggBrSOgF.and m i c r o a n a l y s i s agreed w i t h i t . M i c r o a n a l y s i s : C C a l c u l a t e d f o r C^BrSOgF [%]• 44.59 Found [%] 44.7 7 VI.C. RESULTS AND DISCUSSION The i n t e r c a l a t i o n of bromine ( I ) f l u o r o s u l f a t e i n t o graphite proceeds smoothly.at room temperature over a p e r i o d of 4 8 hours to form a stage 1 i n t e r c a l a t i o n compound C^BrSOgF. The observed r a t e of i n t e r c a l a t i o n appears to be much lower i n the gas phase i n t e r c a l a t i o n compared to both "parent molecules", S 20gF 2 and B r 2 . This could be a t t r i b u t e d to the lower vapour pressure of BrSOgF. The colour change of graphite during i n t e r c a l a t i o n seems to be prominent and e a s i l y observable i n samples made from HOPG when the concen-t r a t i o n of BrSOgF approaches stage 2 or lower. The stage 1 sample appears to be deep-blue and i t s formation can be described by: 12C + BrSO.F »- C, o B r S 0 o F (6.4) 239 The stage 1 compounds prepared from various types of graphite e x h i b i t small v a r i a t i o n s i n t h e i r compositions which may be due to d i f f e r e n c e s i n f l a k e s i z e and the degree of order found i n the l a t t i c e . The absence of Br . e v o l u t i o n during t h i s 2 r e a c t i o n i s conclusive evidence against a mere f l u o r o s u l f o n a -t i o n r e a c t i o n of the type: 14C + 2BrS0 3F *• 2C ?S0gF + Br? (6.5) M i c r o a n a l y s i s and the- observed r a t i o of Br : S : F of 1 :-l. 01:1. 04 are very c o n s i s t e n t with the formulation as C^BrSOgF. I d e n t i f i c a t i o n of C-^2BrS0gF as a stage 1 GIC i s based on the X-ray d i f f r a c t i o n p a t t e r n and the s h i f t of Raman a c t i v e ^ l a t t i c e v i b r a t i o n of graphite to 1641 cm 1 i n 7 agreement wi t h published observations f o r stage 1 acceptor GI Cs. The observed l a y e r - s e p a r a t i o n of C-^BrSOgF i s higher ° 196 than the 7.7 5 A found f o r carbon l a y e r s w i t h a bromine l a y e r i n t e r c a l a t e d between them, but very close to the l a y e r ° 92 separation 7.81 A of C^SOgF. The reported density of BrSOgF 3 at 25°C i s 2.238 g/cm which leads t o a molecular volume of ° 3 about 133 A . This would suggest an " i d e a l " r a t i o of C to BrSOgF to be 11.56 (see Appendix. ) i n very c l o s e agreement with the value of 12.0 i n C^BrSOgF obtained by m i c r o a n a l y s i s and 12.03 c a l c u l a t e d from the weight increase. This a l s o provides evidence f o r a r a t h e r t i g h t l y packed nature of the i n t e r c a l a t e d BrSOgF molecules. Other acceptor i n t e r c a l a n t s such as SbF,-, HN0„ and HS0 oF are known to polymerize e a s i l y 5 3 3 16 7 when i n t e r c a l a t e d i n t o graphite . Molecular a s s o c i a t i o n as 240 i n l i q u i d BrSOgF, evidenced by i t s high b o i l i n g point and Trouton constant, may s t i l l be present i n the i n t e r c a l a t e 19 l a y e r of C-^BrSOgF. The F NMR spectra are r a t h e r u s e f u l i n preparing the GIC without surface adsorbed or condensed BrSOgF remaining i n the sample. Non i n t e r c a l a t e d BrSOgF was observed at 34 ppm f o r a sample of composition C-^ <-BrS0~F according to gravimetry. On prolonged pumping the sample became fre e 19 of a l l non i n t e r c a l a t e d molecules as evidenced by i t s F NMR spectrum. The s i g n a l due to i n t e r c a l a t e d BrSOgF observed at 9.3 ppm i s s h i f t e d to higher f i e l d from that of l i q u i d 92 BrSOgF which i s observed at 34.6 ppm ' . The i n t e r c a l a t i o n .compound C^_BrS0gF i s s t a b l e at 25°C i n vacuo but thermal decomposition at about 100°C r e s u l t s i n some decomposition of the i n t e r c a l a t e . Although no non-. condensible gases were evolved, the Raman spectrum of the v o l a t i l e f r a c t i o n i n d i c a t e d the presence of Br- and BrSOgF. 19 However the F NMR spectrum of the residue compound showed only one s i g n a l i n the region of i n t e r c a l a t e d BrSOgF, no evidence of side r e a c t i o n s such as f l u o r l n a t i o n of the carbon planes was.observed. The formation of Br_ by the decomposition of d e i n t e r c a l a t e d m a t e r i a l at 1.0 0 °C i s rather,-unexpected since 92 o l i q u i d BrSOgF i s reported to be s t a b l e upto 150 C. This observation aroused f u r t h e r i n t e r e s t i n the I n t e r c a l a t i o n of BrSOgF with graphite at about t h i s temperature. Subsequently the i n t e r c a l a t i o n at 105 to 110°C was observed to proceed w i t h the e v o l u t i o n of B r 2 to y i e l d a product of the composition C 2-BrF(S0gF) 2. M i c r o a n a l y s i s on t h i s sample showed a r a t i o 2 41 of Br : S : F of 1 : 2.02 : 2.98. X-ray d i f f r a c t i o n i n d i c a t e d a o stage 1 composition w i t h I = 7.7 6 ± 0.03 A., commensurate with the la r g e s i z e of the i n t e r c a l a t e . The Raman spectrum of t h i s compound showed the E n o v i b r a t i o n a l band at 16 4 5 cm 1 2g2 . . 19 supporting the stage 1 composition. The F NMR of t h i s compound i s shown i n F i g . (6.2). The two s i g n a l s at +9.7 and -84.1 ppm r e s p e c t i v e l y are of the approximate i n t e n s i t y r a t i o 2 : 1 . The s i g n a l w i t h the higher i n t e n s i t y i s i n the range where i n t e r c a l a t e d f l u o r o s u l f a t e s are observed, t h e r e f o r e i t i s assigned to the f l u o r i n e attached to s u l f u r i n the SO^F group. The resonance at -84.1 ppm i s assigned t o f l u o r i n e attached to bromine. While a w e l l defined compound of the composition B r F ( S 0 3 F ) 2 does not e x i s t , with BrF^ and B r ( S 0 3 F ) 3 m i s c i b l e at any p r o p o r t i o n to give viscous m a t e r i a l , according to 93 reported study on t h i s system resonances i n the form of s i n g l e broad peaks are found at -46.5 ppm (Br — F) and %40 ppm ( S — F ) r e l a t i v e to CFC1 3 and can be expected f o r B r F ( S 0 3 F ) 2 . Again a s u b s t a n t i a l u p f i e l d s h i f t of both resonances appears to occur on i n t e r c a l a t i o n , s i m i l a r to the one found f o r C^ 2BrS0 3F and as discussed p r e v i o u s l y f o r C^SC^F. While s u b s t a n t i a l s i m i l a r i t y i s found, no c l e a r view on the s t r u c t u r e and nature of i n t e r c a l a t e d B r F ( S 0 3 F ) 2 i s p o s s i b l e . In a d d i t i o n to the d i f f e r e n c e i n the composition of the r e s u l t i n g GICs the other major d i f f e r e n c e between the r e a c t i o n s of BrSOgF at ambient and elevated temperatures i s the l i b e r a t i o n of B r 0 i n the l a t t e r case. To r a t i o n a l i z e these 242 obser v a t i o n s , the f o l l o w i n g r e a c t i o n sequence i s proposed f o r o the r e a c t i o n at 105-110 C. I n i t i a l d i s p r o p o r t i o n a t i o n of BrSO-F according to equation (6.6): 3BrS0-F = = 5 = Br- + Br(S0gF)g (6.6) i s followed by p a r t i a l decomposition according to equation (6.7) during the i n t e r c a l a t i o n process. B r ( S 0 3 F ) 3 • BrF(S0 3F)- + SOg (6.7) However i t must be emphasized that the proposed d i s p r o p o r t i o n a -n ^ g t i o n w e l l known f o r B r l i s h i t h e r t o not observed f o r BrSOgF 105 i t s e l f . S i m i l a r l y the decomposition step proposed above i s 104 g e n e r a l l y very p l a u s i b l e f o r f l u o r o s u l f a t e s , but studies on t h i s compound have been r a t h e r l i m i t e d . The d i s p r o p o r t i o n a -t i o n of BrSOgF i n the presence of graphite i s not only t o t a l l y unexpected but does not have any d i r e c t precedents. The observation that i n t e r c a l a t i o n , has not caused any notable change i n the chemical r e a c t i v i t y p a t t e r n of BrSOgF i s r e f l e c t e d i n the r e a c t i o n of C-^-BrSOgF with excess S_0 F_ • The i n t e r c a l a t e d BrSO-F i s o x i d i z e d by S-O.F- to form 3 J 2 6 2 Br(S0gF)g r e s u l t i n g i n a GIC of the composition C 1 6 5Br(S0gF)g. o The c a x i s l a y e r repeat distance of 7.92 A and the E2g2 b a n < ^ at 1646 cm 1 i n the Raman spectrum agree w e l l with expectations f o r a stage 1 GIC. However both the stoichiometry and the 19 F NMR spect r a do suggest that not a l l Br (SOgF) _ Is inte r ^ . 243 c a l a t e d i n t h i s m a t e r i a l . Considering the increase i n the carbon to i n t e r c a l a t e r a t i o when going from C-^BrSOgF to C 2gBrF(SOgF) 2, an even higher r a t i o i s expected f o r the i n t e r -c a l a t i o n compound co n t a i n i n g BrCSOgF)^ since i t i s the l a r g e s t among a l l three bromine f l u o r o s u l f a t e s i n t e r c a l a t e d . There-fore the composition C^g gBrCSOgF)^, suggested by micro a n a l y s i s 19 must include some non i n t e r c a l a t e d BrCSOgF)^. The F NMR spectrum of t h i s compound shows two broad resonances (see F i g . (6.3)). The s i g n a l w i t h the lower i n t e n s i t y at 38.3 ppm i s q u i t e close to the l i t e r a t u r e value of f r e e B r ( S 0 3 F ) 3 93 reported to be 3 9.0 ppm r e l a t i v e to CFC1 3 , while the s i g n a l at 10.0 ppm, almost three times as intense as the f i r s t one appears i n the region of the i n t e r c a l a t e d f l u o r o s u l f a t e group. I t appears that the o x i d a t i o n of C-^BrSOgF occurs under e x t r u s i o n of some BrSOgF from the l a t t i c e followed by o x i d a t i o n to give " f r e e " BrCSOgF)^. While some of t h i s m a t e r i a l i s removed with the excess S_0 F„, some of the bromine ( I I I ) 2 b 2 f l u o r o s u l f a t e , a s o l i d at room temperature, remains mixed wit h the i n t e r c a l a t i o n compound. Attempts to separate i n t e r -c a l a t e d and non i n t e r c a l a t e d m a t e r i a l by repeatedly washing w i t h S 20gF 2 were not s u c c e s s f u l . In s p i t e of the complex r e a c t i o n product t h i s experiment confirms that i n t e r c a l a t e o x i d a t i o n l e a d i n g to a stage 1 compound i s p o s s i b l e . The packing of i n t e r c a l a t e l a y e r s along the c-axis d i r e c t i o n o seems to be r a t h e r t i g h t , the l a y e r separation of 7.92 A observed f o r C, r c B r ( S 0 o F ) o seems very small f o r a l a r g e l b . o o o i n t e r c a l a t e such as Br(S0 3F)g. However i f one assumes that 2 44 the planar c o o r d i n a t i o n around bromine suggested f o r Br(SO-F)g i s r e t a i n e d on i n t e r c a l a t i o n the observed separation becomes p l a u s i b l e . The s u c c e s s f u l o x i d a t i o n of i n t e r c a l a t e BrSOgF to Br(S0 3F)_ can be reversed by r e a c t i n g the m a t e r i a l C-^gBrtSO-F) with excess Br-. The r e s u l t i n g product i s i d e n t i f i e d by 19 gravimetry, m i c r o a n a l y s i s and F NMR as the stage 1 graphite bromine ( I ) f l u o r o s u l f a t e , C-^-BrSOgF. This reduction process can be explained by equation (6.8) : 3C--Br(SO-F)- + 3Br 0 • 4C.„BrS0oF + 5BrS0 oF l b o 6 2 1I 6 5 (6.8) The e x t r u s i o n of some of the i n t e r c a l a t e i n C-^B^OgF by S-OgF_ and the o x i d a t i o n of the remaining i n t e r c a l a t e to Br(SO-F). as w e l l as the subsequent reduction with Br. f o l l o w 92 93 105 published precedents ' ' on the neat compounds c l o s e l y . Formation of a n i o n i c f l u o r o s u l f a t e complexes according to 198 19 9 equation (6.9) has been found p r e v i o u s l y with a l k a l i : metals ' MSO-F + BrSOgF • MBr(SO-F)- (6.9) where M = L i , Na, Cs A l l our attempts to s t a b i l i z e t h i s anion with the macro c a t i o n were unsuccessful. As i n the p r e v i o u s l y discussed attempt to react C-.S0-F with HSOgF, graphite f l u o r o s u l f ate close to i t s l i m i t i n g composition i s l a r g e l y unreactive towards BrSOgF 19 as w e l l . The F NMR evidence suggests only surface adsorption 245 or c a p i l l a r y condensation of BrSOgF. As shown i n F i g . (6.1) the resonance due to BrSOgF appears at 32.2 ppm r e l a t i v e to CFC1- a f t e r incomplete evacuation of the sample. Continuous pumping r e s u l t s i n only one s i g n a l which appears i n the region where both i n t e r c a l a t e d BrSOgF and SO-F are observed. The bromine content of 1.8 8% of t h i s compound as determined by mi c r o a n a l y s i s shows that the i n t e r c a l a t e remains p r i m a r i l y as SOgF ions w i t h the bromine c o n t a i n i n g i m p u r i t i e s e i t h e r i n t e r c a l a t e d or surface adsorbed. The r e a c t i o n of C-^BrSOgF with excess HSOgCFg was • attempted i n the hope of s y n t h e s i z i n g the i n t e r c a l a t i o n compound C nBrS0~CF-. Since the s o l v o l y s i s of CySOgF w i t h HSOgCFg r e s u l t e d i n the compound ^-SOgCFg ' a s i m i l a r r e a c t i o n w ith C-^BrSOgF should form the compound BrSOgCFg i n the i n t e r c a l a t e l a y e r s . However the e v o l u t i o n of Br^ i n d i c a t e d a d i f f e r e n t type of r e a c t i o n and the f i n a l product was confirmed 19 . . by F NMR, X-ray d i f f r a c t i o n and m i c r o a n a l y s i s to be the p r e v i o u s l y discussed graphite t r i f l u o r o m e t h y l s u l f a t e , C-^SOgCFg, suggesting the r e a c t i o n as i n equation (6.10) w i t h 127 12 8 HSOgF r e a c t i n g f u r t h e r w i t h HSOgCFg ' to form v o l a t i l e 199 products. The compound BrSOgCFg i s known to be unstable 2C 1 2BrSOgF + 2HS0^CFg • 2C 1 2SOgCFg + B r 2 + HSOgF (6.10) above 0 C, t h e r e f o r e the formation of C 1 2S0gCFg instead of C BrSO^CF. i n the s o l v o l y s i s r e a c t i o n Is not unexpected, n 3 3 J 246 A s i m i l a r r a t i o n a l e may e x p l a i n the observations i n the 92 r e a c t i o n of C-^BrSOgF with B r 2 - Previous work on the B r 2 - BrSOgF system suggested t h a t a thermally l a b i l e compound of the type Br QSO qF might e x i s t at lower temperatures, r which would d i s s o c i a t e at room temperature. When the i n t e r -c a l a t i o n compound C-^BrSOgF i s reacted with excess Br^ , i t seems th a t some of the BrSOgF molecules present i n the g a l l e r i e s are replaced by Br^ molecules. The Raman spectrum of the product before exposing to a dynamic vacuum shows a band at 240 cm 1 i n a d d i t i o n to the E 0 „ band at 1645-1647 cm 1. 2g2 The v i b r a t i o n a l band of f r e e Br^ molecule should appear at -1 10 9 7 316 cm but the i n t e r c a l a t e d bromine i s reported to show I t s major v i b r a t i o n a l band at 240 cm ^. At t h i s stagerthe i n t e r c a l a t e l a y e r s may contain BrSOgF and B r 2 , p o s s i b l y . a s BrgSOgF, but the l i m i t e d s t a b i l i t y of t h i s product r e s u l t s i n the l o s s of Br 2- As described e a r l i e r the GIC co n t a i n i n g BrSOgF i s vacuum s t a b l e at room temperature. Again the f i n a l product contains only BrSOgF with some vacant g a l l e r i e s . The observed weight decrease when going from C^BrSOgF to the f i n a l product -could be a t t r i b u t e d t o the BrSOgF molecules l o s t during the r e a c t i o n with B r 2 to accomodate the B r 2 molecules or the bulky BrgSOgF species. When t h i s r e a c t i o n was attempted i n the opposite manner i . e . by r e a c t i n g CgBr wit h excess BrSOgF, the f i n a l product i s the stage 1 compound C 1 2BrS0gF. This could be a t t r i b u t e d to the very high s t a b i l i t y of GICs c o n t a i n i n g BrSOgF compared to those c o n t a i n i n g B r 2 . Hence a l l of the i n t e r c a l a t e d B r 2 molecules were replaced by 247 BrSO-F and the composition v a r i e s from C 0Br to C. oBrS0-F. The i n t e r l a y e r separations observed i n a l l GICs contain-ing bromine f l u o r o s u l f a t e s f a l l below 8.0 A, suggesting a t i g h t l y packed s t r u c t u r e between bound carbon l a y e r s and the i n t e r c a l a t e s . The p r i n c i p a l f a c t o r which c o n t r i b u t e s to such t i g h t e r packing i s the Coulomb a t t r a c t i o n between carbon and i n t e r c a l a t e l a y e r s . The p h y s i c a l data f o r these GICs are 19 summarized i n Table (6.2). The measured F chemical s h i f t data are compared to l i t e r a t u r e data f o r pure i n t e r c a l a n t s . The strong charge t r a n s f e r involved i n these i n t e r c a l a t i o n compounds i s r e f l e c t e d i n t h e i r E_ n v i b r a t i o n a l modes, where 2g2 a s h i f t of approximately 6 0 cm 1 towards higher frequency from that of p y r o l y t i c graphite i s observed f o r stage 1 compounds 19 c o n t a i n i n g bromine f l u o r o s u l f a t e s . The F NMR s p e c t r a of these GICs show the s i g n a l due to S — F resonance s h i f t e d to higher f i e l d by 25-30 ppm upon i n t e r c a l a t i o n while an even l a r g e r s h i f t i s found f o r the B r — F resonance. While s u f f i c i e n t evidence has been found f o r the existence of BrSOgF, BrF(S0-.F)- and Br (SOgF) i n the g a l l e r i e s and t h e i r f u n c t i o n as acceptors i n the charge t r a n s f e r process, two p o i n t s s t i l l remain unsolved: ( i ) the exact extent of charge t r a n s f e r , and: ( i i ) the anions formed i n the i n t e r c a l a t e l a y e r s during the charge t r a n s f e r . Anions such as BrCSO^F)" 1 9 8 ' 1 9 9 and Br(SO-F)" 1 9 8 which are TABLE 6.2: SOME PHYSICAL PROPERTIES OF GRAPHITE BROMINE FLUOROSULFATES PHYSICAL PROPERTIES OF THE GIC CHEMICAL SHIFT OF INTERCALANT INTERCALATION COMPOUND o I (A) c v (cm 6 (ppm) E, '2g2 6(ppm) REFERENCE C 1 2 B r S 0 3 F 7.75 1641 9.3 34.6 92 C 2 0 B r F ( S 0 3 F ) 2 7.76 1645 9.7 40 . 0 93 @ @ 14.1 -46 . 5 93 C 1 6 B r ( S 0 3 F ) 3 7.92 1646 10.6 39.0 93 r e l a t i v e to ex t e r n a l CFC1, @ due to F attached to Br 249 w e l l e s t a b l i s h e d i n the form of a l k a l i , metal s a l t s as well.as of the type B r S O g F may e x i s t i n the i n t e r c a l a t e l a y e r s of graphite b r o m i n e f l u o r o s u l f a t e s . VI. C. INTERCALATION OF CHLORINE CD FLUOROSULFATE' INTO  GRAPHITE VI. C. 1." CHEMICAL BEHAVIOUR OF CHLORINE CD FLUOROSULFATE Chl o r i n e (I) f l u o r o s u l f a t e , CISOgF, i s the only binary f l u o r o s u l f a t e of c h l o r i n e reported so f a r . This compound, a yellow l i q u i d at room temperature , can be made by a" high temperature r e a c t i o n (12 5 C) i n v o l v i n g C l ^ and S,-,OgF2 or may be produced from C1F and SO^ 1^. The handling of t h i s substance i s somewhat complicated by i t s extreme moisture s e n s i t i v i t y , r e q u i r i n g a metal container f o r i t s p r e p a r a t i o n . I t r e a c t s with even t r a c e amounts of moisture i n glass t o give 9 3 a red viscous l i q u i d resembling C10 2S0gF m appearance. The r e a c t i o n s of CISOgF resemble i n p r i n c i p l e those of BrSOgF, except f o r those i n v o l v i n g e i t h e r r e d u c t i o n or o x i d a t i o n of 1 9 3 . . . . c h l o r i n e , which are not p o s s i b l e m t h i s system. In contrast to BrSOgF, of the "parent" molecules of CISOgF only S 2 0 6 F 2 e a n ' b e i n t e r c a l a t e d t o y i e l d s t a b l e GICs as discussed e a r l i e r . VT. C 2. SYNTHETIC REACTTON In a t y p i c a l react ion an excess of (>5' -mD CISOgF was d i s t i l l e d upon 0.2 87 3 g of SP 1 graphite powder and the 250 mixture was allowed to react f o r 24 hours at room temperature. The v o l a t i l e s , presumably CI- and CISOgF were removed i n vacuo and the sample maintained i n a dynamic vacuum u n t i l constant weight was reached. A blue-black product of 0.5552 g was 19 obtained. The F NMR spectrum of t h i s sample showed a s i n g l e resonance at 10.0 ppm. F i r s t stage composition of t h i s sample was confirmed by X—ray d i f f r a c t i o n and the c-axis l a y e r repeat o distance T was determined as (7.71 - 7.78) A. M i c r o a n a l y s i s c on t h i s sample i n d i c a t e d the presence of a very small amount of c h l o r i n e presumably as CISOGF i n the g a l l e r i e s and suggested a composition of C-^ "5gS0gF-0.12 CISOgF. Microanalysis-C S F CI Calculated f o r C l l 5 8 S 0 3 F ' 0 - 1 2 C 1 S 0 3 F f % l 54.69 14.10 8.37 1.67 Found ['%] 52.60 13 . 60 8.03 1 . 64 VI.C.3. RESULTS AND DISCUSSION The r e a c t i o n of CISOgF with graphite r e s u l t s pre-dominantly i n f l u o r o s u l f o n a t i o n , where the SOgF ions occupy 19 most of the g a l l e r y spaces. The F NMR spectra of samples analyzed a f t e r a short pumping showed a strong s i g n a l at 10 ppm and a weak broad resonance at ^3 4 ppm. Since the 118 l a t t e r peak i s i n very c l o s e agreement to 33.9 ppm observed f o r C1S0-F i n h i g h r e s o l u t i o n spectra i t i s a t t r i b u t e d to 251 surface adsorbed or c a p i l l a r y condensed CISOgF. This peak disappears on continuous evacuation, c o n s i s t e n t w i t h the proposed assignment. I t seems l i k e l y that CISOgF i s i n i t i a l l y i n t e r c a l a t e d before the cleavage of C I — 0 bond occurs to form the graphite f l u o r o s u l f a t e as evidenced by the Raman spectra of the sample before evacuation under r e l e a s e of C l j . The F2g2 v l ^ a t i o n a l mode observed at an approximate composition of "Cj^ClSO-F" based on gravimetry i s shown i n F i g . (6.5) together with the same v i b r a t i o n a l mode observed f o r C-^BrSOgF. The doublet observed f o r " C ^ C I S O - E " i n d i c a t e s that the i n t e r c a l a t e l a y e r s may contain a considerable, amount of CISOgF showing a stronger component of the doublet at 1641 cm . When t h i s sample i s evacuated t o reach, constant weight only a s i n g l e band Is observed at 1631 cm The. p o s i t i o n of t h i s band i s i n c l o s e agreement with, t h a t of the E 0 - band of & 2g2 stage 1 graphite f l u o r o s u l f ate., CySOgF. M i c r o a n a l y s i s of the f i n a l product also i n d i c a t e s the r e t e n t i o n of a very small amount of c h l o r i n e . While an average composition of C l l 58^°3 F"°" 1 2 CISOgF seems to be p l a u s i b l e , the lower value of carbon contents observed i s i n d i c a t i v e of some inhomogenity i n the sample. The small amount of CISOgF i n t e r c a l a t e d may not be homogeneously d i s t r i b u t e d i n the g a l l e r i e s . Nevertheless the mag.-or r e a c t i o n t a k i n g place In t h i s system i s best expressed by equation (.6.11).. 2nC + 2C1S0-F * 2C SO„F + C l 0 n 3 2 C 6 . l l ) 252 253 Separate preparations of t h i s sample showed the i n t e r l a y e r o separation to vary w i t h i n the range of 7.71 - 7.98 A, which o i s very c l o s e to 7.81 A observed f o r CySO^F. In summary while CISOGF does seem to i n t e r c a l a t e i n i t i a l l y , i t subsequently r e l e a s e s C^- However t h i s method does not provide samples which are completely f r e e of c h l o r i n e . In a d d i t i o n the r e s u l t s i n d i c a t e the formation of predominantly stage 1 materials- with, a r a t h e r high C : SO^F r a t i o of 10.3 rendering t h i s method l e s s s u i t a b l e than the d i r e c t i n t e r c a l a t i o n of SO^F by r e a c t i n g with 520^2-VT.D. ATTEMPTED INTERCALATION OF IODINE" (I) FLUOROSULFATE VI. D„l. CHEMICAL •BEHAVIOUR_ OF IODINE (T)- FLUOROSULFATE Iodine (I) f l u o r o s u l f a t e , ISO^F, i s a black-brown 9 4 c r y s t a l l i n e s o l i d (melting point 50.2°C). I t i s moisture s e n s i t i v e and thermally s t a b l e up to 150°C. In i t s chemical r e a c t i o n s ISO^F would f u n c t i o n as a m i l d o x i d i z i n g and f l u o r o s u l f o n a t i n g agent"^ 5. VI.D.2. SYNTHETIC REACTION The r e a c t i o n of ISOgF was attempted on HOPG p i e c e s , since i t i s r a t h e r i m p r a c t i c a l to separate a f i n e powder from the h i g h l y viscous melt. In a t y p i c a l r e a c t i o n 0.0759 g of HOPG pieces were mixed with an excess (about 5.0 g) of f r e s h l y prepared ISOgF powder i n the dry box. The mixture was heated to 7 0°C and maintained at t h i s temperature f o r 254 about 4 8 hours under magnetic s t i r r i n g . The sample was removed from the r e a c t i o n mixture under N_ atmosphere while the ISOgF was s t i l l i n the l i q u i d s t a t e . A brown-black product covered by excess ISO^F which had s o l i d i f i e d on the edges and surface was obtained. This sample was cleaved i n the dry box to remove the top l a y e r s and the edges where ISO^F c r y s t a l s 19 s t i l l remained. The F NMR of t h i s sample showed a resonance centered at 44.6 ppm and there was no s i g n a l In the region of i n t e r c a l a t e d f l u o r o s u l f a t e s . VI.D.3. RESULTS AND DISCUSSION Iodine (I) f l u o r o s u l f a t e , ISO^F does not appear to i n t e r c a l a t e i n t o graphite under the c o n d i t i o n s of the e x p e r i -ment. The 1 9 F NMR spectra of HOPG pieces reacted w i t h IS0 3F melt showed evidence f o r the presence of ISO^F adsorbed or c r y s t a l l i z e d on gr a p h i t e . There was no evidence f o r the presence of i n t e r c a l a t e d SO-F~ e i t h e r , which argues against the p o s s i b i l i t y of ISO-F f u n c t i o n i n g as a f l u o r o s u l f o n a t i n g agent. The i n a b i l i t y of IS0-.F to i n t e r c a l a t e i n t o graphite shows that i t behaves l i k e I_ i t s e l f which,as described e a r l i e r , does not meet the energy requirements to open the g a l l e r i e s i n graphite to i n i t i a t e the i n t e r c a l a t i o n . Nevertheless compounds such as IC1, IBr and IF,- have been found to i n t e r -c a l a t e i n t o graphite . 255 VI.E. CONCLUSION The halogen ( I ) f l u o r o s u l f a t e s , XSOgF, (where X = C l , Br, I) show d i f f e r e n t types of i n t e r a c t i o n s with gra p h i t e . At room temperature BrSOgF forms GICs with C-^BrSOgF as the l i m i t i n g composition. The oxidation, of i n t e r c a l a t e d BrSOgF by S-O-F^ . r e s u l t s i n the formation of the bromine ( I I I ) 2 6 2 f l u o r o s u l f a t e , Br(S0gF)g i n the g a l l e r i e s . The i n t e r a c t i o n of BrSOgF with graphite at 105-110°C r e s u l t s i n the i n t e r c a l a t i o n compound of the composition Q.^ Q^rF( SOg F) ^  • C h l o r i n e ( I ) f l u o r o s u l f a t e , CISOgF, appears to f u n c t i o n p r i m a r i l y as a f l u o r o s u l f o n a t i n g agent forming graphite f l u o r o s u l f a t e , w i t h some c h l o r i n e r e t a i n e d p o s s i b l y as CISOgF i n the g a l l e r i e s . Iodine (I) f l u o r o s u l f a t e , ISOgF, does not i n t e r c a l a t e i n t o graphite under the usual experimental c o n d i t i o n s . 256 CHAPTER VII ELECTRICAL CONDUCTIVITY OF FLUOROSULFATE CONTAINING INTERCALATION COMPOUNDS AND THEIR DERIVATIVES 257 CHAPTER VII ELECTRICAL CONDUCTIVITY OF FLUOROSULFATE CONTAINING INTERCALATION COMPOUNDS AND THEIR DERIVATIVES V I L A INTRODUCTION General Comment The preceding sections ..dealt e x t e n s i v e l y with s y n t h e t i c and s t r u c t u r a l aspects of f l u o r o s u l f a t e c o n t a i n i n g or -derived GICs. The i n t e r c a l a t i o n studies described there had involved almost e x c l u s i v e l y SP 1 gr a p h i t e , r a r e l y HOPG and even more r a r e l y n a t u r a l graphite as s t a r t i n g m a t e r i a l s . Synthetic p r i n c i p l e s e s t a b l i s h e d there are ap p l i e d i n the present chapter to HOPG p l a t e s w i t h sample a n a l y s i s r e s t r i c t e d to gravimetry r a t h e r than complete a n a l y s i s and f u l l c h a r a c t e r i -z a t i o n by spectroscopic means. The c o n d u c t i v i t y data obtained and discussed here are intended t o be of a more ex p l o r a t o r y than comprehensive nature to complement s t r u c t u r a l conclusions on GICs. The e l e c t r i c a l c o n d u c t i v i t y measurements on GICs have been c a r r i e d out p r i m a r i l y by two d i f f e r e n t techniques: ( i ) D i r e c t contact method, best i l l u s t r a t e d by the "Four Po i n t " technique, and ( i i ) Contactless techniques, i l l u s t r a t e d by a r e c e n t l y 258 developed r a d i o frequency i n d u c t i o n technique. FOUR POINT DIRECT CONTACT TECHNIQUE The low r e s i s t i v i t y of GICs was f i r s t discovered by 5 Ubbelohde employing the four p o i n t contact technique. This l>+7 conventional technique was adopted by others m the next few years. During the l a s t decade, a sudden increase i n i n t e r e s t i n the c o n d u c t i v i t y of GICs generated a " c l o s e r look" at t h i s technique which r e s u l t e d i n considerable u n c e r t a i n t y i n the r e s u l t s obtained by four p o i n t r e s i s t i v i t y measurements on GICs. The fundamental requirement f o r r e l i a b l e measurements i n a four p o i n t contact technique are uniform current i n j e c t i o n through the sample and an ohmic contact between the sample and the t e r m i n a l s . The f i r s t c o n d i t i o n i s i d e a l l y s a t i s f i e d by an i s o t r o p i c sample. But graphite and i t s i n t e r c a l a t i o n compounds e x h i b i t various degrees of a n i s o t r o p y , which i s normally described by 0a-/ac where a a and °c are the c o n d u c t i v i -t i e s of the sample along the a and c axes r e s p e c t i v e l y . As described e a r l i e r i n Chapter I [>see f o r e.g. Table (l...l)].the anisotropy of graphite decreases when i t i s i n t e r c a l a t e d w i t h e l e c t r o n donors, but i n t e r c a l a t i o n with acceptor species r e s u l t s i n increased anisotropy. The GICs which show very high planar c o n d u c t i v i t y e x h i b i t the highest anisotropy (>10 ). Therefore, the i n j e c t e d current i n these samples would not be uniformly d i s t r i b u t e d over the whole volume but would concen-t r a t e i n those l a y e r s where the current lead makes good 2 5 9 e l e c t r i c a l contact so that the e f f e c t i v e conducting cross-s e c t i o n a l area would be l e s s than the geometrical area of the sample. Some of the disadvantages of using the four point d i r e c t contact method l i e i n the l i n e of p r a c t i c a l problems inv o l v e d i n t h i s technique. Most of the i n t e r c a l a n t s ( f o r e.g. HSOgF, SbF 5, AsFg) used to prepare acceptor GICs are extremely c o r r o s i v e and would p o s s i b l y r e a c t with the metal contacts even i f these were made of noble metals. In a d d i t i o n to t h i s the graphite piece would expand along the d i r e c t i o n of the c-axis during the i n t e r c a l a t i o n , stage 1 compounds are known to be of more than twice the thickness of o r i g i n a l g r a p h i t e . Phenomena l i k e " b l i s t e r i n g " and bubble formation on graphite surface termed " e x f o l i a t i o n " often occur during i n t e r c a l a t i o n . A l l these cause problems i n maintaining good e l e c t r i c a l c o n t a c t s , r e s u l t i n g In unce r t a i n e l e c t r i c a l conduc-t i v i t y values. A d d i t i o n a l problems are caused by d e i n t e r c a l a -t i o n due to l o c a l heating of the sample during the c o n d u c t i v i t y measurements which makes i t necessary to maintain a very low current i n the c i r c u i t . Hence one has to use larg e specimens to generate detectable voltage changes i n the h i g h l y conducting acceptor GICs. When i n v o l v i n g large samples, inhomogenity of the i n t e r c a l a t e may be manifested i n the c o n d u c t i v i t y measurements and t h i s would a f f e c t the r e p r o d u c i b i l i t y and hence the r e l i a b i l i t y of the measurements. Due to the above mentioned d e f i c i e n c i e s , the four p o i n t method i s r a r e l y used f o r c o n d u c t i v i t y measurements on GICs 260 made from HOPG, however s l i g h t l y modified forms of t h i s technique have r e c e n t l y been used f o r samples made from graphite 202 fiber-CONTACTLESS TECHNIQUES There are various types of c o n t a c t l e s s techniques described i n the l i t e r a t u r e . A r e c e n t l y published review 2 03 a r t i c l e summarized these techniques which have been success-f u l l y a p p l i e d f o r m e t a l l i c conductors and semiconductors. In a d d i t i o n to being f r e e of a l l the problems encountered i n the conventional method, t h i s technique permits c o n d u c t i v i t y measurements on samples confined i n simple sealed glass tubes, thus avoiding the i n t r o d u c t i o n of metal to glass seals i n the system. The primary advantages of t h i s method are: ( i ) i t can be used w i t h c o r r o s i v e i n t e r c a l a n t s . ( i i ) i t allows making i n - s i t u c o n d u c t i v i t y measurements. ( i i i ) the composition of the GICs may be checked by g r a v i -metry i f the c e l l i s s u i t a b l y designed, and ( i v ) i nstrumental c a l i b r a t i o n can be made by using metal p l a t e s . Various c o n t a c t l e s s methods using power d i s s i p a t i o n 2 0 3 i n tank c i r c u i t s of o s c i l l a t o r s have been adapted f o r GICs Among these the r . f . induction, technique using a f e r r i t e 2 0 4 2 0 5 core or an a i r - c o i l have been modified over the years 261 and are commonly used to measure the e l e c t r i c a l c o n d u c t i v i t y of GICs. This technique measures the c o n d u c t i v i t y only along the basal planes and i s t h e r e f o r e i n s e n s i t i v e to the degree of anisotropy. FERRITE CORE RADIO FREQUENCY INDUCTION SYSTEM A f e r r i t e core r . f . i n d u c t i o n technique was introduced r e c e n t l y to measure e l e c t r i c a l c o n d u c t i v i t y of GICs and has found wide acceptance. I t i s the method of choice i n t h i s study. The technique r e q u i r e s a uniform magnetic f i e l d around the sample during c o n d u c t i v i t y measurements. This c o n d i t i o n i s met by i n t r o d u c i n g the sample i n t o a f e r r i t e core i n which the magnetic f i e l d i s provided by a d r i v i n g c o i l operated at r a d i o frequency. The eddy current induced i n the sample i s detected by a sensing c o i l . The f u n c t i o n of major constituents of the f e r r i t e core r . f . i n d u c t i o n system are o u t l i n e d below and a d e s c r i p t i o n of the p h y s i c a l aspects of t h i s technique 204 can be found i n the l i t e r a t u r e . The c i r c u i t diagram of the system constructed f o r t h i s purpose i s shown i n F i g . (7.1). A c i r c u l a r f e r r i t e core (6.0 cm diameter) was cut on one side to provide the a i r gap, necessary to i n s e r t the sample tube. The width of t h i s a i r gap was kept to the minimum p o s s i b l e s i z e (1.0 cm) to produce a reasonably uniform magnetic f i e l d . Surface dimensions of the samples used (approximately 5 mm x 5 mm) were much smaller than the dimensions (1.25 cm) of the edges of the core. This would minimize the f r i n g i n g f i e l d 2 0 4 • e f f e c t s . The d r i v i n g c o i l i s attached to the o s c i l l a t o r , CONTACTLESS R.F INDUCTION TECHNIQUE Ref: C.Zeller, A.Denenstein and G.M.T. Foley Rev. Sci.Instrum. 50, 602 (1979) Sensing coil IOOJJFE Ferrite core Driving coil r 33 kn I I 3M ={= O.OIjjF^ fi T T 1.2 kn 1.0 ka 1.2 kn 4.05 V •\ 0.47/iF Hr FIG. 7.1 6 o Oscillator frequency = 1 6 kHz balanced signal output (so C D ro 263 while the sensing c o i l i s connected to a half-wave r e c t i f i e r 1 which together with the r e s i s t a n c e - c a p a c i t a n c e network would convert the A.C. s i g n a l detected to a D.C. voltage. The output t e r m i n a l s are connected to a nanovoltmeter ( K e i t h l e y Model 148, f u l l scale a d j u s t a b l e from 10 nanovolts to 100 m i l l i v o l t s ) . By a d j u s t i n g the potentiometer system the output p o t e n t i a l d i f f e r e n c e can be n u l l e d when there i s no sample i n the a i r gap of the f e r r i t e core. The glass tube c o n t a i n i n g the sample i s then i n s e r t e d i n t o the a i r gap and the output s i g n a l (AV) i s recorded from the nanovoltmeter. This p o t e n t i a l d i f f e r e n c e i s r e l a t e d to the c o n d u c t i v i t y of the sample by the , .. , • 28b,204 • r e l a t i o n s h i p ' : AV = K t s 2 c (7.1) t = thickness of the sample [cm] 2 s = surface area of the sample [cm ] a = e l e c t r i c a l c o n d u c t i v i t y of the sample [ohm 1 cm K = constant A t r a v e l l i n g microscope and a toolmaker's micrometer were used to measure t and s r e s p e c t i v l y . During i n - s i t u measure-ments extending over s e v e r a l hours, a small d r i f t i n the output voltage was noted. This might p o s s i b l y have been caused by a s l i g h t increase i n temperature i n t h e : f e r r i t e core. Subsequently the output voltage was readjusted to n u l l p o i n t without the sample i n the a i r gap i f a d r i f t i n voltage was 264 noted. The observed values of the induced voltage V were _ 3 i n the order of mV (10 V) f o r HOPG pieces of the p r e v i o u s l y mentioned dimensions. The working p r i n c i p l e of t h i s method i s based on the assumption that the induced eddy current i s approximately constant through the whole thickness of the sample. However, according to b a s i c electromagnetic theory, the current d i s t r i b u t i o n along the c-axis of the sample decreases exponen-t i a l l y with distance from the.surface. The distance at which the eddy current becomes equal to e 1 f r a c t i o n (approximately 13! 3 7%) of the current on the s u r f a c e , i s c a l l e d the s k i n depth 204 The value of s k i n depth (60 can be expressed by; •a) ii a s 1/2 (7.2) where co • = o s c i l l a t o r frequency a p p l i e d to the d r i v i n g c o i l y g = p e r m e a b i l i t y of the m a t e r i a l e l e c t r i c a l c o n d u c t i v i t y Since most of the samples are non-magnetic, the p e r m e a b i l i t y of the m a t e r i a l can be assumed to be equal to that of 204 vacuum Hence equation (7.2) can be reduced to 1/2 _5 TT 0)0" (7.3) 265 When the o s c i l l a t o r frequency u> i s expressed i n kHz and the c o n d u c t i v i t y a i n yQ 1 cm 1 , the s k i n depth <5 w i l l be i n mm. To achieve approximately uniform current along the c-axis through the e n t i r e t hickness ( t ) of ther.sample: 6 >> - (7.4) 2 According to equation (7.3), the sk i n depth 6 would increase only i f the frequency UJ i s reduced. But the achievement of s u f f i c i e n t s i g n a l to noise r a t i o i n the output voltage r e q u i r e s the operation of the system at a h i g h frequency. To optimize co n d i t i o n s an operating frequency of 16.8 kHz was chosen a f t e r s e v e r a l t r i a l s . For our system the skin, depth at t h i s frequency would be 0.39 mm according to equation (7.3). This would r e q u i r e that the thic k n e s s of the samples used.for c o n d u c t i v i t y measurements be l e s s than 0.7 8 mm. The thickness of the samples used i n t h i s study were i n the range of (0.3 -0.4) mm. In order to use t h i s system f o r measuring e l e c t r i c a l c o n d u c t i v i t y of GICs, i t has t o be c a l i b r a t e d by determining the value of the constant K i n equation (7.1). The value of t h i s constant i s dependent on the dimensions and shape of the samples to be used. Since the samples of GICs used i n t h i s study had approximate dimensions o f 5 mm x 5 mm x 0.3 mm, the samples used to c a l i b r a t e the system were also made i n the same dimensions. These samples were cut from pieces of metals w i t h known e l e c t r i c a l c o n d u c t i v i t i e s which were checked by 266 means of "D.C. - four p o i n t " measurements on ribbon shaped samples. The l i s t of metals used to c a l i b r a t e the system and t h e i r e l e c t r i c a l c o n d u c t i v i t i e s are given i n Table (7.1). The output voltage AV was measured f o r each of these samples i n the f e r r i t e core r . f . Induction system. A p l o t of AV 2 against ( t s a) f o r the data obtained with these metals was used to determine the value of K. The slope of t h i s s t r a i g h t l i n e p l o t i n d i c a t e d the value of K to be 0.0436. By using the c a l i b r a t e d system the conductivitie.s ' of several.. HOPG . pieces 4 -1 -1 were measured and an average value of 2.3 2 x 10 ohm cm , 14 '4- -1 i n good agreement with the reported value of 2. 5 x 1-0' ohm cm 1 was obtained. * TABLE 7.1: ELECTRICAL CONDUCTIVITY OF METALS USED FOR CALIBRATION OF THE R.F. INDUCTION SYSTEM Metal C o n d u c t i v i t y (ohm cm ) Cu 5 . 9 x 10 5 A l 3.5 x 10 5 Brass 1.4 x 10 5 S t a i n l e s s S t e e l 304 1.4 x 10 4 Pb 4. 8 x 10 4 267 VII.B. PREPARATION OF SAMPLES FOR CONDUCTIVITY MEASUREMENTS I d e a l l y one should prepare GICs from good q u a l i t y c r y s t a l l i n e graphite to measure t h e i r e l e c t r i c a l c o n d u c t i v i t i e s . But the d i f f i c u l t i e s encountered i n ob t a i n i n g such c r y s t a l s from n a t u r a l graphite a f t e r removing the i m p u r i t i e s pose serious problems. A s u i t a b l e s u b s t i t u t e i s available, i n h i g h l y o r i e n t e d p y r o l y t i c graphite (HOPG). I t i s obtained i n large pieces of high p u r i t y and inr spite, o f i t s _ p b l y c r y s t a l l i n e nature has been widely used as the s t a r t i n g m a t e r i a l f o r the preparation of GICs. The use of HOPG i n e l e c t r i c a l conduc-t i v i t y measurements no doubt , has allowed the generation of f a i r l y r e l i a b l e , reproducible- and c o n s i s t e n t c o n d u c t i v i t y data. The samples used i n t h i s study were prepared from HOPG which was vacuum d r i e d at 150°C f o r 24 hours immediately before use. A l l c o n d u c t i v i t y measurements were made at room temperature The i n t e r c a l a t i o n r e a c t i o n s were c a r r i e d out using the apparatus shown i n F i g . (7.2). A l l r e a c t i o n s f o l l o w i n respect to r e a c t i o n temperature and time, c l o s e l y those used i n the pre p a r a t i v e s e c t i o n with HOPG s u b s t i t u t e d f o r SP 1 gr a p h i t e , however i n some instances appropriate m o d i f i c a t i o n s of the s y n t h e t i c procedure were necessary. They are described i n t h i s s e c t i o n . The HOPG piece was confined i n a quartz tube which had two glass rods i n s i d e to keep the. sample i n a h o r i z o n t a l p o s i t i o n [see F i g . ( 7 . 2 ) ] . This tube was equipped w i t h a 268 Graphite Quartz Cell O r 6 V O Pressure Gauge To Pump Intercalant FIG. 7.2 APPARATUS FOR THE PREPARATION OF GICs FOR ELECTRICAL CONDUCTIVITY MEASUREMENTS 269 Kontes Teflon stem stopcock and could be attached to a vacuum l i n e f o r a d d i t i o n of i n t e r c a l a n t s onto the graphite p i e c e , or detached from the vacuum l i n e to be weighed i n order to determine the composition of the sample. In a t y p i c a l p reparation a grap h i t e piece of known weight was placed i n a quartz tube and the t o t a l weight was determined a f t e r evacuating i t . The tube was then Inserted i n t o the a i r gap of the f e r r i t e core with the HOPG piece p a r a l l e l to i t s cross s e c t i o n and the induced voltage (AV ) recorded. This piece was then converted to the GIC of the desired composition v i a vapour or l i q u i d phase i n t e r c a l a t i o n , and the induced voltage (AV) was determined. V I I . B . l . PREPARATION OF- BINARY GRAPHITE FLUOROSULFATES AND  GRAPHITE ACID FLUOROSULFATES (a) PREPARATION--QF BINARY GRAPHITE FLUOROSULFATES Binary graphite f l u o r o s u l f a t e s , C SO-F, were prepared by vapour phase i n t e r c a l a t i o n of S_0_F_. The HOPG piece was exposed to a pressure of about (20-25) t o r r f o r periods of ^5 minutes. A f t e r each r e a c t i o n the system was evacuated and the weight of the i n t e r c a l a t e d piece of graphite deter-mined. Samples of various compositions were prepared and the corresponding voltage changes were measured. Thickness measurements of samples at the i n i t i a l stages of i n t e r c a l a t i o n were made by a t r a v e l l i n g microscope. But when the sample compositions approached stage 2 or lower, the r e l i a b i l i t y of 270 these measurements decreased due to extreme edge f r a y i n g i n the sample. At t h i s stage samples were taken i n t o the dry box and t h e i r thickness were measured by a toolmaker's micrometer. The r e a c t i o n was very r a p i d at the i n i t i a l stages even at the low pressure of i n t e r c a l a n t used, but to prepare samples of lower stages (^  stages 2 or 1) the pressure had to be increased to (150-180) t o r r . Gradual colour changes of the sample during the i n t e r -c a l a t i o n were evident. Compounds with stage i n d i c e s higher than three appeared s i l v e r y , as the i n t e r c a l a t i o n proceeded, a b l u i s h t i n t was observed and f i n a l l y a dark blue product of composition C^  ^SO^F was obtained. I t was found that r a t h e r uniform samples of stage 1 composition could be obtained by c o n t r o l l i n g the pressure of S^OgF^, r e s u l t i n g i n a slower r e a c t i o n r a t e . Extensive e x f o l i a t i o n , apparent c l e a v i n g and the formation of gaps between graphite planes a l l i n d i c a t i v e of h i g h l y exothermic o x i d a t i v e i n t e r c a l a t i o n could thus be avoided. (b) PREPARATION OF GRAPHITE ACID FLUOROSULFATES Graphite a c i d f l u o r o s u l f a t e s , CnS03F-mHSOgF, were prepared by both successive and simultaneous i n t e r c a l a t i o n methods as described i n Chapter I I I . ( i ) SUCCESSI'VE INTERCALATION Binary graphite f l u o r o s u l f a t e s , C S0„F, of stage 2 or 271 higher were f i r s t prepared by exposing the HOPG to vapour of S-O-F2 at room temperature according to the procedure described i n the preceding s e c t i o n . These samples were subsequently exposed to an excess (^ 3 ml) of HSO-F l i q u i d f o r ^24 hours. A f t e r removing the excess a c i d i n vacuo the samples were maintained i n a dynamic vacuum u n t i l constant weight was reached. The ac i d f l u o r o s u l f a t e s prepared by t h i s method appeared darker compared t o the shiny blue colour of the binary f l u o r o s u l f a t e s . The thickness of the sample as w e l l as the induced voltage were measured as o u t l i n e d before. The amount of ac i d i n t e r c a l a t e d and the o v e r a l l composition were deduced from the Increase i n weight i n the second step. ( i i ) SIMULTANEOUS INTERCALATION This was achieved by a l l o w i n g the HOPG piece to re a c t with a mixture of S-O-F. and HSO-F at room temperature. The 2 b 2 6 amount of S o0_F i n the mixture was c o n t r o l l e d so that the 2 b I o x i d a t i o n of graphite could only take place to a l i m i t e d extent. For example to prepare a sample of composition C* SO-F~•2HS0-F, the amount of S o 0 r F o i n the r e a c t i o n mixture I H 5 o I b I was l i m i t e d to the exact amount required f o r the q u a n t i t a t i v e o x i d a t i o n of the HOPG piece to C-^ so tha t n e u t r a l a c i d molecules can i n t e r c a l a t e i n t o the g a l l e r i e s along with the SO-F~ ions r e q u i r e d to maintain e l e c t r i c a l n e u t r a l i t y i n the system. In a t y p i c a l r e a c t i o n about 3 ml of HSOgF were d i s t i l l e d over the HOPG piece at -198°C and whil e maintaining the HOPG 272 and'HSOgF at t h i s temperature, the c a l c u l a t e d amount of ^>2^Q^2 was d i s t i l l e d i n t o the system. A c a l i b r a t e d micro p i p e t t e was used to t r a n s f e r the S^O^F^ wit h the amount f i r s t determined 2 b 2 by volume and then more a c c u r a t e l y by weight. The reaction, mixture was allowed to warm up to room temperature. The excess l i q u i d was removed i n vacuo a f t e r 2 4 hours, and the sample was maintained i n a dynamic vacuum u n t i l i t s weight remained constant. The composition of the product was c a l c u l a t e d w i t h the f o l l o w i n g assumptions: ( i ) a l l of the S_0_F o reacted to form the corresponding C + 2 6 2 ° n stage, and ( i i ) the d i f f e r e n c e between the observed weight of the product and the expected weight of the corresponding binary f l u o r o s u l f a t e C^SO^F was due to the n e u t r a l a c i d molecules that were i n t e r c a l a t e d r a t h e r than surface adsorbed or c a p i l l a r y condensed. VII.B.2. PREPARATION OF GRAPHITE BROMINE FLUOROSULFATES I n t e r c a l a t i o n of bromine f l u o r o s u l f a t e , BrSOgF, was c a r r i e d out i n the same manner as described f o r S o0 rF„ except, 2 o 2 the r e a c t i o n had t o be c a r r i e d out w i t h l i q u i d BrSOgF to prepare GICs of stages 2 or lower, due to the low vapour pressure of BrSOgF. Excess l i q u i d was removed i n vacuo a f t e r a s p e c i f i c r e a c t i o n time which v a r i e d from 15 minutes to s e v e r a l hours ( f o r a stage 1 compound). The i n t e r c a l a t i o n of 273 BrSOgF vapour as w e l l as l i q u i d took place smoothly without c l e a v i n g of the HOPG piece. The r e a c t i o n of the stage 1 graphite bromine f l u o r o -s u l f a t e , C, oBrS0 oF, with excess S o0 F showed e f f e c t s of ± A o 2 b 2 exothermicity r e s u l t i n g i n samples with v i s i b l e gaps between graphite l a y e r s . VII.B.3. PREPARATION OF GRAPHITE TRIFLUOROMETHYLSULFATES AND  GRAPHITE HEXAFLUOROANTIMONATES The graphite t r i f l u oromethylsulf ates , C^OgCFg and graphite hexafluoroantimonates, C nSbFg, were prepared by r e a c t i n g the corresponding graphite f l u o r o s u l f a t e s , C nSOgF, with an excess of HSOgCFg and SbFg r e s p e c t i v e l y . The only d i f f e r e n c e between these two r e a c t i o n s was the long r e a c t i o