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Electron-deficient porphyrins Terazono, Yuichi 2001

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ELECTRON-DEFICIENT  PORPHYRINS  by YUICHI  TERAZONO  B . E n g . , K u m a m o t o University, Japan, 1987 M . E n g . , K u m a m o t o University, Japan, 1989  A THESIS SUBMITTED I N PARTIAL F U L F I L L M E N T O F THE REQUIREMENTS  F O RT H E D E G R E E O F  DOCTOR OF  PHILOSOPHY  in T H E F A C U L T Y O F G R A D U A T E STUDIES Department o f Chemistry  W e accept this thesis as c o n f o r m i n g to the requited standard  T H E UNIVERSITY O F BRITISH C O L U M B I A July 2001 (C) Y u i c h i T e r a z o n o , 2001  In  presenting this  degree at the  thesis  in  University of  partial  fulfilment  of  of  department  this thesis for or  by  his  or  requirements  British Columbia, I agree that the  freely available for reference and study. I further copying  the  representatives.  an advanced  Library shall make it  agree that permission for extensive  scholarly purposes may be her  for  It  is  granted  by the  understood  that  head of copying  my or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department The University of British Columbia Vancouver, Canada  DE-6 (2/88)  11  ABSTRACT T h e search for effective porphyrin catalysts for oxygenations that m i m i c the functions o f cytochrome P-450  has  led  to  the  synthesis  P-ttifluoromerhyl-OT^-tetJ:aphenylporphyrins  of  were  electron-deficient prepared  by  trifluoromethylation using P-bromo-w^o-tetraphenylporphyrins  porphyrins.  the  Novel  copper  assisted  and in-situ generated C F C u via 3  the pyrolysis o f C F C 0 N a / C u I or the metathesis o f trifluoromethylcadmium ( ( C F ) C d 3  2  3  2  +  C F j C d B r / C u B r ) . A l t h o u g h multiple trifluoromethylation was difficult due to the steric bulk o f the — C F group, the existence o f various ^wo-tetraphenylporphyrins w i t h perfluoroalkyl moieties 3  was affirmed. Partially trifluoromethylated porphyrins H T P P ( C F ) 2  H TPP(CF ) 2  3  Zn(TPPBr ) 4  ( 4 8 a ) , and H T P P ( C F ) ( C F C F ) (52a)  4  2  (45b)  Fe(TPP(CF ) )Cl 3  4  3  foUowed  by  3  2  3  demetallation.  3  2  2  ( 4 6 a ) , H TPP(CF ) ( 4 7 a ) , 2  3  3  were obtained by trifluoromethylation o f  Zn(TPP(CF ) ) 3  ( 4 8 f ) , and F e ( T P P ( C F ) ( C F C F ) ) C l (52c) 3  3  3  4  ( 4 8 b ) , C o ( T P P ( C F ) ) (48e) 3  4  were also synthesized from  the  corresponding free-base porphyrins. These metalloporphyrins, as well as free-base porphyrins, were used for the analysis o f the electronic and the steric effects o f the — C F groups o n the 3  Ph C F ,  Ph C F  3  46a  F C 3  Ph  48a 48b 48e 48f  : : : :  M= M= M= M=  2H  +  Zn(II) Co(II) Fe(III)Cl  F C 3  Ph 5 2 a : M = 2 H 52c : M = Fe(III)Cl +  Ill  porphyrin macrocycle by UV-visible and H N M R spectroscopy, cyclic voltammetry, and l  X-ray  crystallography.  These  analyses  not  only  suggested  that  novel  p-trifluoromethylporphyrins were electron-deficient but also showed that those porphyrins take bacteriochlorin-like distorted electronic structures; a fixed 187t-electronic pathway. A n X-ray crystal structure of 48b  revealed severe macrocycle distortion into a saddle shape due to  the steric interaction between the —CF and the meso-phenyl groups. Catalytic oxidations of 3  cyclohexane and cyclohexene using 48f  and 52c  as catalysts, iodosylbenzene (PhIO) as an  oxidant and the above-mentioned substrates showed that they were not superior to one of the best porphyrin catalysts, Fe(TDCPPCl )Cl (10d) 8  and porphyrin 48f  and 52c  were not very  stable in the oxidation runs. Although the prepared novel porphyrins were not satisfactory as P-450  model  compounds,  interesting  electronic  and  structural  properties  of  the  zwj-0-tettaphenylporphyrins partially trifluoromethylated at the pyrrolic P-positions of antipodal pyrroles were revealed. The steric and electronic effects of the —CF groups on the pyrrolic 3  P-positions of zmo-teteaphenylporphyrin were also compared to those of P-methyl analogues (57a,  58a,  59a,  and 59b)  in order to compare these effects distincdy.  Ph C H ,  Ph C H /-IN  Ph—(\  A r = 2,6-dichlorophenyl  HC 3  s  Ph 3  58a  ,N=/ M //-Ph  Ph 59a : M = 2 H  +  59b : M = Zn(II)  IV  T A B L E OF C O N T E N T S  ABSTRACT  n  TABLE OF CONTENTS  iv  LIST OF TABLES  vii  LIST OF FIGURES  viii  LIST OF SCHEMES  xi  LIST OF ABBREVIA TIONS NOMENCLATURE  xii xvii  ACKNOWLEDGEMENT  xix  CHAPTER I A. I n t r o d u c t i o n  1 1  B. M e t a l o p o r p h y r i n s as c y t o c h r o m eP 4 5 0m o d e lc o m p o u n d s  5  1. Cytochromes P-450 5 a. Distribution, nomenclature, and structure 5 b. Function and mode of action 6 c. Mechanisms of hydrocarbon oxidation 8 (1) Mechanism of alkane hydroxylation 8 (2) Mechanism of alkene epoxidation 9 2. Synthetic metalloporphyrins as P-450 rnirnics 11 a. Structures of porphyrins that appear in this section 11 b. Synthetic methods for the major players in the early development of P-450 mimics 12 (1) Condensation of pyrrole with arylaldehydes 12 (2) p-Perchlorinated and perbrominated meso-arylporphyrins c. Early development of P-450 mimics d. Electron-withdrawing effects on catalytic activities  13 14 16  e. Newer generation of electron-deficient porphyrins  22  (1) P-Perfluoro-meso-tetraatylporphyrins (2) P-Nitro-meso-tetrakis(2,6-dichlorophenyl)porphyrins (3) meso-Tetrakis(perfluoroalkyl)porphyrins 3. Design concept for a new P-450 mimic a. Basic concept b. Potential advantages of trifluoromethyl substituents  22 25 28 30 30 31  C. S y n t h e t c i s t r a t e g y for P t r i f l u o r o m e t h y l a t i o n of m e s o t e t r a p h e n y p lo r p h y r n i 1. Brief overview of trifluoromethylation a. Fluorination of an existing aryl substituent (Scheme 1-3) b. Introduction of trifluoromethyl groups (1) Transfer of CF " (Scheme l-4(a)) 3  32 33 33 33  32  (2) Transfer of C F (Scheme l-4(b)) 2. C o p p e r assisted trifluoromethylation  ,  +  3  34 35  a. C F C u from pyrolysis o f sodium trifluoromethyl acetate i n the presence o f Cu(I) halide  35  b. C F C u f r o m metathesis o f trifluorometiiylcadmium w i t h Cu(I) halide (1) Trifluoromethylation (2) Synthesis of trifluoromethylcadmium  37 37 37  3  3  D . Analysis of porphyrins  38  1. U V - v i s i b l e absorption spectroscopy a. Characteristics o f U V - v i s i b l e absorption spectra o f porphyrins and metalloporphyrins  38  b. Electron-withdrawing effects o n U V - v i s i b l e absorption spectra 2. R e d o x potentials o f porphyrins  41 43  a. General redox properties o f porphyrins i n non-aqueous media (1) Technique, solvent, and supporting electrolytes (2) Porphyrin ring redox properties in free-base and metalloporphyrins (3) Iron porphyrins b. Effects o f substituents o n the redox potentials o f derivatives o f T P P (1) Aryl-ring-substituted T P P s (2) fJ-Substituted TPPs (3) Conclusion 3. H N M R spectroscopy a. P o r p h y r i n ring current effect b. Concentration effect c. N - H tautomerism  43 43 44 44 47 47 49 54 55 55 55 57  l  4. Spectrophotometric  titration  a. Evaluation o f p K , o f N H b. Determination o f central metal — ligand b i n d i n g constant  E . Goals of this thesis  38  59 59 61  63  CHAPTER II  64  A. Synthesis of P-trifluotomethyl- and P-methyl-weso-tetraphenylporphyrins 1. Trifluoromethylation  64 65  a. Synthesis o f precursors 66 b. Trifluoromethylation by pyrolysis o f C F C 0 N a / C u l 67 (1) Reaction using Cu(TPPBr ) (7c) 67 (2) Reactions using M T P P B r ( M = Zn(II), Cu(II), and Ni(II)) (45b,45c,and 45d) 69 c. Trifluoromethylation by C F C u generated by the metathesis o f tiifluorometiiylcadmium and C u B r 72 (1) Preliminary experiments 72 (2) Optimization of the yield for P-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin....76 2. Methylation 88 3. Metallation 90 a. Synthesis o f Zn(II) and Co(II) complex o f 48 91 3  2  8  4  3  b. Synthesis o f Fe(III) complexes o f 48 and 52 4. Summary  B. Analysis of P-trifluoromethyl-weso-tetraphenylporphyrins..../  92 95  95  VI  1.  UV-visible spectra of synthesized novel porphyrins a. Free-base porphyrins (1) UV-visible spectra in C H C 1 (2) Absorbance vs. concentration of 48a b. UV-visible spectra of metalloporphyrins 2. N M R spectroscopy 2  97 98 98 109 110 116  2  •  a. Determination of electronic pathway of P-tdfluoromethylporphyrins  117  b. Unusual ' H N M R chemical shift for pyrrolic p-protons of H T P P ( C F ) (48a) 3. Redox potentials  126 134  a. Free-base P-trifluoromethyl-^m-tetraphenylporphyrins b. Zn(II) porphyrins c. Fe(III) porphyrins 4. Crystal structures a. Preparation of the crystals and crystallographic data b. Structure details (1) Core size, Z n displacement, and axial coordination  136 144 151 153 153 155 155  (2) Effects o f antipodal P-substitation (3) Macrocycle distortion (4) Orientation of the axial ligand 5. Specttophotometric  161 164 169 172  2  titration  a. Titration of 48a with strong organic bases in CH Ci2 (1) Titration with D B U (2) Titration with E t N b. Titration of Co(rPP(CF ) ) (48e) with pyridine and imidazole 2  3  3  4  6. Summary C. Catalytic oxidation of cyclohexane and cyclohexene CHAPTER  III  3  4  173 173 176 176 182 184 188  A. Conclusions  188  B. Future work  189  CHAPTER  IV  195  A. Chemicals  195  B. Instrumentation  195  C. Procedures  197  D . Preparation of materials  202  REFERENCES  220  APPENDICES  233  A. UV-visible spectra of diacids of 48a and 59a  233  B. Crystallographic Data  234  vii  LIST O F T A B L E S Table 1-1. Table 1-2.  Yields o f typical (3-perhalogenation reactions Relationship between catalyst i r o n redox potentials a n d activities  Table 1-3. Table 1-4. Table 1-5.  O" values for different substituents T h e first reduction and oxidation potentials for 36 - 39 F o r m a t i o n constants for pyridine b i n d i n g i n C H C 1 at 25 ° C  31 54 62  Table Table Table Table  Results o f trifluoromethylation by the pyrolysis m e t h o d Trifluoromethylation by metathesis using M T P P B r (45) Products obtained by the reaction at 70 ° C for 88 h R values for metal-free perfluoroalkylated porphyrins  71 75 78 79  2-1. 2-2. 2-3. 2-4.  2  p.14 19  2  4  f  Table 2-5. Table 2-6. Table 2-7.  Isolated P-perfluoroalkyl-^fo-tetraphenylporphyrins C o m p a r i s o n o f U V - v i s i b l e absorption maxima U V - v i s i b l e absorption maxima o f metalloporphyrins  82 99 114  Table 2-8.  C h e m i c a l shift values o f Zn(II) P-tetrasubstituted wt?.ra-tettaphenylporphyrins  133  Table 2-9.  R e d o x potentials o f P-substituted wwo-tetraphenylporphyrins i n C H C 1 . 140  Table 2-10.  R e d o x potentials o f P-substituted ^.r^teteaphenylporphyrin Zn(II) complexes i n C H C 1 R e d o x potentials o f Fe(III) porphyrin chloride complexes Crystallographic data for 45b-(MeOH)-(DMF), 48b-(EtOH) , and 59b-(THF) -(CHCl ) Core size, selected b o n d lengths a n d b o n d angles  2  2  Table 2-11. Table 2-12.  Table 2-14. Table 2-15. Table 2-16.  3  B-l-a B-l-b B-2-a B-2-b B-3-a B-3-b  154 159  04  Cp-Cp b o n d lengths i n antipodally P-tetrasubstituted ^^o-tetraphenylporphyrins 164 B i n d i n g constants o f Co(II) porphyrins for base b i n d i n g i n i n C H C 1 . . . 182 O x i d a t i o n o f cyclohexane and cyclohexene using Fe(III) porphyrins a n d iodosylbenzene i n C H C 1 185 2  2  Table Table Table Table Table Table  147 152  2  3  16  Table 2-13.  2  2  2  A t o m i c coordinates a n d B for Z n ( T P P ( C F ) ) - ( E t O H ) 234 A n i s o t r o p i c displacement parameters for Z n ( T P P ( C F ) ) - ( E t O H ) 236 A t o m i c coordinates a n d B for Z n ( T P P B r ) - ( M e O H ) - ( D M F ) 238 A n i s o t r o p i c displacement parameters for Z n ( T P P B r ) - ( M e O H ) - ( D M F ) . 2 4 0 A t o m i c coordinates and B for Z n f T T ^ C H ^ - C I H F ) , - ( C H C l ) 242 A n i s o t r o p i c displacement parameters for ZnCrPP(CH ) )-CiHF) -(CHCl ) . 244 e q  3  4  3  3  c q  4  3  4  4  e q  3  4  16  6  3  0  4  3  0 4  Vlll  LIST O F F I G U R E S Figure 1-1.  P r o t o p o r p h y r i n F X F e complex  Figure 1-2.  Examples o f electron-deficient porphyrins  p.l 2  Figure 1-3.  E x a m p l e o f salen M n ( I H ) complex  Figure 1-4.  A c t i v e site and hydrophobic pocket o f cytochrome P - 4 5 0  Figure 1-5.  Catalytic cycle o f cytochrome P-450  Figure 1-6.  M e c h a n i s m o f alkane hydroxylation by cytochrome P-450  Figure 1-7.  M e c h a n i s m o f the oxidation o f olefins by cytochrome P-450  10  Figure 1-8.  Porphyrins used i n P-450 m o d e l studies  11  Figure 1-9.  Reaction o f oxo Fe(FV) porphyrin Tt-cation radical w i t h alkene and /-BuOOH  18  Figure 1-10.  3 5  cam  7  Catalytic cycle for isobutane hydroxylation by 0  2  9  and 8d proposed by Ellis  and L y o n s  20  Figure 1-11. Figure 1-12. Figure 1-13.  Synthesis o f p-polynitto-OT^-tefi:alds(2,6-dicUorophenyl)porphyrins Synthesis o f wm>-tetJ:aMs(perfluoroalkyi)porphyrins R e m o v a l o f water by use o f a toluene-azeotrope i n the  26 29  Figure 1-14.  pentafluoroethylation o f a-iodonaphthalene U V - v i s i b l e spectra o f « ? ^ - t e t r a p h e n y l p o r p h y r i n s C H C 1  36 39  Figure 1-15.  Symmetries o f Z n ( T P P ) (2b), H T P P (2a) and [ H T P P ]  Figure 1-16.  E x a m p l e o f the U V - v i s i b l e spectral change by electron-withdrawing  2  2  2  40  2 +  4  effects  42  Figure 1-17.  Cyclic voltammogram o f H T P P (2a) i n C H C 1  Figure 1-18.  Cyclic voltammogram o f F e ( T P P ) C l (2d) i n C P ^ C h .  46  Figure 1-19.  Plot o f E  48  Figure 1-20.  First reduction and oxidation potentials vs, # o f C N groups for (a)  Figure 1-21.  P l o t o f the first oxidation and the first reduction potential for  2  1 / 2  2  45  2  vs. 4a for the electrode reactions o f H TP(/>-X)P (31a) 2  H T P P ( C N ) (34a) and (b) C u T P P ( C N ) (34c) 2  S  51  x  F e f T P P B r J C l (35a) using P h C N as solvent Figure 1-22.  52  Side view o f the crystal structures o f H T M P (3a), H T M P C 1 2  H TMPBr 2  4  2  (36),  4  (37), and H T M P C 1 (38) 2  53  8  Figure 1-23.  200 M H z H N M R spectrum o f H T P P (2a) i n C D C 1 at 298 K  Figure 1-24.  P l o t o f ' H chemical shift o f meso-Hvs. porphyrin concentration for 40a. 58  56  Figure 1-25.  Tautomerism i n H T P P (2a)  Figure 1-26.  Relative populations o f 42a and 42b at 200 K i n C D C 1  Figure 2-1.  U V - v i s i b l e spectra during trifluoromethylation o f 45b at 70 °C  77  Figure 2-2.  U V - v i s i b l e spectra during trifluoromethylation o f 45b at 110 ° C  81  Figure 2-3.  3,4-Dibromopyrrole and 3,4-bis(trifluoromethyl)pyrrole modeled by  Figure 2-4.  U V - v i s i b l e spectra o f the orange c o m p o u n d and H T P P ( C F ) (48a)  Figure 2-5.  U V - v i s i b l e spectra o f P-tafluorometiiyl-wwo-tettaphenylporphyrins,  }  2  3  59  2  2  60  2  HyperChem  84 2  (b)47a, and (c)48a i n C H C 1 2  Figure 2-6.  2  3  87  4  (a)46a, 101  U V - v i s i b l e spectra o f P-tetrabromo-OTc?j(9-tetraphenylporphyrins (45a) i n CH C1 2  2  102  IX  F i g u r e 2-7.  UV-visible spectra of P-memyl-w^o-tettaphenylporphyrins, ( a)57a, (b)58a,  and ( c ) 5 9 a in CH C1 103 UV-visible spectra of 5 2a in C H C 1 106 UV-visible spectra of bacteriochlorin (64) 108 UV-visible spectral change of H T P P ( C F ) (48a) Ill UV-visible spectral change of H T P P ( C F , ) ( C F C F ) (52a) 112 UV-visible spectra of Zn(TPP(CF ) ) (48b) and Co(TPP(CF ) ) (48e) in CH C1 : 113 UV-visible spectra of [Fe(TPP(CF ) )]Cl ( 4 8 f ) , [FeTPP(CF ) (CF CF )]Cl ( 5 2 c ) , and [Fe(TPPBr )]Cl (45e) 115 400 M H z *H N M R spectra of H T P P B r (45a) in CDC1 at room temperature 118 400 M H z ' H N M R spectra of H T P P ( C F ) (47a) in CDC1 at room temperature 120 400 M H z C O S Y spectra of H T P P ( C F ) (47a) 121 2  F i g u r e F i g u r e F i g u r e F i g u r e F i g u r e  2-8. 2-9. 2-10. 2-11. 2-12.  2  2  2  3  4  2  3  3  2  F i g u r e 2-13.  2  2  3  4  3  4  4  3  3  2  3  2  3  4  F i g u r e 2-14. F i g u r e 2-15. F i g u r e 2-16. F i g u r e 2-17. F i g u r e 2-18.  2  4  3  2  3  2  3  3  3  3  18^-electron pathway of H T P P ( C F ) (47a) 122 200 M H z ' H N M R spectra of H T P P ( C F ) (47a) in the presence of and in the absence of residual water in CDC1 123 400 M H z ' H N M R spectra of H T P P ( C H ) (58a) in CDC1 at room temperature 125 200 M H z ' H N M R spectra of (a) H T P P (2a), (b) H T P P B r ( 4 5 a ) , (c) H T P P ( C F ) (48a) and (d) H T P P ( C H ) (59a) in C D at room temperature 127 400 M H z ' H N M R spectra of diacid of (a) H T P P ( C F ) ( 4 8 a ) , (b) H T P P B r (45a) and (c) H T P P ( C H ) (59a) in T F A - d at room temperature 130 Structures of (a) [ H T P P ] and (b) [ H T P P ( C H ) ] 132 2  3  3  2  3  3  3  F i g u r e 2-19. F i g u r e 2-20.  2  3  3  4  2  2  3  4  6  4  2  3  4  6  2  2  F i g u r e 2-22. F i g u r e 2-23.  3  2  2  F i g u r e 2-21.  3  3  4  4  2+  2+  4  4  3  4  Cyclic voltammograms of (a) H T P P ( C F ) (46a) and (b) H T P P ( C F ) 137 Cyclic voltammograms of H T P P ( C F ) (48a) at different scan rates 138 Cyclic voltammograms of (a) H T P P ( C H ) ( 5 7 a ) , (b) H T P P ( C H ) ( 5 8 a ) , and (c) H T P P ( C H ) (59a) 139 Redox potentials of (a) H T P P ( C F ) (x = 0 (2a), 2 ( 4 6 a ) , 3( 4 7 a ) , and 4 ( 4 8 a ) ) and (b) H T P P ( C H ) (x = 0 (2a), 2 ( 5 7 a ) , 3( 5 8 a ) , and 4 ( 5 9 a ) ) .. 143 Energy level diagram for H O M O s and L U M O s of the four generic metalloporphyrin classes 145 2  3  2  2  3  3  (47a)  F i g u r e 2-24. F i g u r e 2-25.  2  2  F i g u r e 2-26.  3  F i g u r e 2-28.  4  3  2  2  3  3  4  2  2  F i g u r e 2-27.  3  2  3  3  X  X  (a) Cyclic voltammogram of Zn(TPP(CF ) ( 4 8 b ) . (b) 4a vs. 1st oxidation 3  4)  and 1st reduction potentials of P-tetrasubstituted mesotetraphenylporphyrinato Zn(II) (Zn(TPP) (2b), Zn(TPPBr ) ( 4 5 b ) , Zn(TPP(CF ) ) ( 4 8 b ) ) 4  3  Zn(TPP(CN) (34b, 4  4  F i g u r e 2-29.  x=4), 146  The H O M O - L U M O gap of P-substituted wao-arylporphyrin Zn(II) complexes 149 F i g u r e2 3 0 4 5 b . X-ray crystal structures of 45b-(MeOH)'(DMF) 156 F i g u r e2 3 0 4 8 b . X-ray crystal structures of 48b- (EtOH) 157 F i g u r e2 3 0 5 9 b . X-ray crystal structures of 59b-(THF) -(CHCl ) 158 3  16  3 04  X  Figure 2-31.  Schematic illustration of the steric effects of antipodal (3-substituents and meso-phenyl groups on the macrocycle of (3-tetrasubstituted mesotetraphenylporphyrin  163  Figure 2-32.  Perpendicular atomic displacements of the Z n porphyrins, relative to the N mean plane 166  Figure 2-33. Figure 2-34.  Orientations of phenyl and C F , groups in 48b Orientations of phenyl and C H groups in 59b  Figure 2-35.  UV-visible spectral change in titration of H T P P ( C F ) (48a) with D B U in CH C1 174 Logarithmic analysis of the spectral data for the addition of D B U to H T P P ( C F ) (48a) in C H C 1 175 UV-visible spectral change in titration of H TPP(CF ) (48a) with E t N in CH C1 177 Titration of Co(TPP(CF ) ) (48e) in C H C 1 with pyridine at 25.0 ° C 178 Spectral changes in the pyridine addition to Co(TPP(CF ) )-(Py)(48e-(Py)) inCH Cl at25.0°C 179 Logarithmic analysis of the spectral data for the addition of pyridine to Co(TPP(CF ) )(48e) in C H C 1 181  4  3  2  Figure 2-36  3  2  Figure 2-38. Figure 2-39.  3  4  4  2  2  3  4  2  3  2  3  4  2  2  3  2  Figure 2-40.  2  2  2  Figure 2-37.  168 170  4  2  3  4  2  2  Figure 4-1.  Electrochemical cell and electrodes  196  Figure 4-2.  Possible isomers for (3-tris(tjifluoromemyl)-OTWt9-tetraphenylporphyrin..210  Figure A - l .  UV-visible spectra of freebase porphyrins, H T P P ( C F ) (48a) and H T P P ( C H ) (59a) in C H C 1 and their diacids in C H C 1 containing 0.5%(v)TFA 2  2  3  4  2  2  3  2  4  2  233  XI  L I S T OF S C H E M E S S c h e m e 1-1. S c h e m e 1-2. S c h e m e 1-3. S c h e m e 1-4. S c h e m e 1-5. S c h e m e 2-1. S c h e m e 2-2.  Synthesis of w^o-tetraarylporphyrins  36  Trifluoromethylation strategies  66  3  2  Trifluoromethylation of P-octabromo-wwo-tetraphenylporphyrinato by pyrolysis of C F C 0 N a / C u I 3  Cu(II) 68  2  Trifluoromethylation of P-tetrabromo-^j'o-porphyrins CF C0 Na/CuI 3  S c h e m e 2-4.  14 33 34  Trifluoromethylation of aromatic halide by pyrolysis of C F C 0 N a  (7c)  S c h e m e 2-3.  p.12  P-Halogenation of /W^ro-tetraarylporphyrin Fluorination of an existing aryl substituent Introduction of a triiluoromethyl group  (45) by pyrolysis of 70  2  Trifluoromethylation of P-tetrabromo-wi?j"o-porphyrins (45) by metathesis of C F - C d / C u B r / H M P A 74 Product distribution in trifluoromethylation of 45b by metathesis at 70, 90, 3  S c h e m e 2-5. S c h e m e S c h e m e S c h e m e S c h e m e  2-6. 2-7. 2-8. 2-9.  S c h e m e 2-10. S c h e m e 2-11.  S c h e m e 3-1. S c h e m e 3-2.  and 110 °C Methylation of 45b Insertion of Zn(II) and Co(II) into H T P P ( C F )  (48a) (48f) and Fe(TPPBr )Cl (45e) (a)187t-electron pathway of bacteriochlorin (64) and (b) the possible 2  Synthesis of Fe(TPP(CF ) )Cl 3  4  3  4  4  85 89 91 93  electronic pathway of p-trifluoromethylporphyrins 108 Atom designations used in Table 2-13 155 Schematic representation of macrocyclic distortion and axial coordination in 45b-(MeOH), 59b-(THF), and 48b(EtOH) 171 wwo-Tettaltis(2,6-bis(trifluoromethyl)phenyl)porphyrin  (66)  Formation of oxo Fe(rV) porphyrin u-cation radical from Fe(III) porphyrin and hydrogen peroxide  192 194  xii  LIST OF ABBREVIATIONS Abs. ArCF Arl B br, bs  Absorbance Trifluoromethyl aryl compound Iodo aryl compound Lewis base Broad, broad singlet Butyronitrile /-Butyl Calculated C F C d X + (CF ) Cd, X = CI or Br Concentrated  3  BuCN  t-Bu Calcd. CF -Cd Cone. 3  3  Co(TP(z>-OCH )P) Co(TPFPPF ) 8  Co(TPP(CN) ) 4  CofTPPFg) Cu(TPP(CN)0 Cu(TPP) Cu(TPPBr ) 4  Cu(TPPBr ) 8  Cys d  3  3  2  5,10,15,20-Tetralds(4-memoxyphenyl)porphyrinatocobalt(Ii) 2,3,7,8,12,13,17,18-Octafluoro-5,l 0,15,20tetralris(perfluorophenyl)porphyrrnatocobalt(Ii) 2,3,12,13-Tetracyano-5,l 0,15,20tetraphenylporphyrinatocobalt(II) 2,3,7,8,12,13,17,18-Octafluoro-5,l 0,15,20tettaphenylporphyrmatocobalt(II) P-Polycyano-5,10,15,20-tetraphenylporphyrinatocopper(Ii) 5,10,15,20-Tetraphenylporphyrinatocopper(H) 2,3,12,13,-Tetrabromo-5,l 0,15,20tetraphenylporphyrinatocopper(II) 2,3,7,8,12,13,17,18-Octabromo-5,10,15,20tetraphenylporphyrinatocopper(II) Cysteine Doublet  DBU  l,8-Diazabicyclo[5.4.0]undec-7-ene  DDQ DMF DMSO  2,3-Dichloro-5,6-dicyanoquinone N,N-Dimethylformamide Dimethylsulfoxide  E v (1) E £ (1) E°; (2)  First half-wave oxidation potential First half-wave reduction potential Second half-wave oxidation potential  (2) EI  Second half-wave reduction potential Electron impact  eq.  Equimolar  Et£> Et N EtOH  Diethylether Trietiiylamine Ethanol Formula weight  2  2  3  F.W. FAB Fc/Fc  Fast atom bombardment Ferrocene/ferrocenium  +  Fe((C F ) P)Cl 3  7  4  Chloro[5,10,15,20tetiakis(heptafluoropropyl)porphyrinato]rron(IIi)  Fe(TDCPP)Cl  CUoro[5,10,15,20-tetrakis(2,6chcHorophenyl)porphyrmato]iron(III) CWoro[2,3J3,12,13 17,18-octabromo-5 10,15 20-terj:akis(2,6cUcMorophenyl)porphyrmato]iron(III)  Fe(TOCPPBrg)Cl  )  Fe(TDCPPCl )Cl 8  8  Fe(TMP)Cl Fe(TP(w-X)P)Cl Fe(TP(/)-X)P)Cl Fe(TPCPP)Cl Fe(TPCPPCl )Cl 8  Fe(TPFPP)Cl FeCTPFPPBr^Cl  FefTPFPPF^Cl FeCrPP(CF )3(CF CF ))Cl 2  Fe(rPP(CF ) )Cl 3  4  [FeCrPP(CF ) ] 0 3  4  2  Fe(TPP(CN) )Cl 4  Fe(TPP)Cl  Fe(TPPBi )Cl 4  GC h H (CF ) P H DPP H TDCPP 3  4  2  2  H H H H  2  2  2  2  TDCPP(N02) TMP TMPBr TMPBr  H TMPC1 2  4  8  4  H TP(/>-X)P H TPCPP 2  2  ChJoro[2,3,7 8,12,13,17,18-octachloro-5,10,15,20-tetrakis(2,6dicmorophenyl)porphyrinato]iron(III) CMom[2,3JA12,13,17,18-octafluoro-5,10,15,20-tetrakis(2,6cUchlorophenyl)porphyrinato]iron(III) C h l o r o ( 5 , l 0,15,20-tetomesitylporphyrinato)iron(III) C h l o r o [5,10,15,20-tetrakis (3-substituted phenyl)porphyrinato]iron(III) Chloro[5,10,15,20-tetrakis(4-substituted phenyl)porphyrinato]iron(III) CUoro[5,10,15,20-tetralds(percUorophenyl)porphyrinato] Chloro[2,3,7,8,12,13,17,18-octachloro-5,10,15,20tettakis(percUorophenyl)porphyrmato]iron(III) CUoro[5,10,15,20-teUakis(perfluorophenyl)porphyrinato]iron( C h l o r o [2,3,7,8,12,13,17,18-octachloro-5,l 0,15,20tettakis(perfluorophenylphenyl)porphyrinato]iron(III) Chloro[2,3,7,8,12,13,17,18-octafluoro-5,10,15,20tettakis(perfluorophenyl)porphyrinato]iron(IIi) C h l o r o [7,8,17 -tris (trifluoromethyl) -18-pentafluoroethyl5,10,15,20-tetraphenylporphyrinato]iron(III) Chloro[7,8,l 7,18-tetxakis(trifluoromethyl)-5,l 0,15,20tetraphenylporphyrinato]iron(III)  3  (u-Oxo)bis [2,3,12,13-tetealds(trifluoromemyl)-5,l 0,15,20tetraphenylporphyrinatoiron(Iir)] Chloro(2,3,12,l 3-tetracyano-5,10,l 5,20tetraphenylporphyrinato)iron(III) C h l o r o ( 5 , l 0,15,20-tetraphenylporphyrinato)iron(Iir) Chloro(7,8,l 7,18-tetrabromo-5,l 0,15,20teteaphenylporp>hyrinato)iron(III) Chloro(P-polybromo-5,l 0,15,20-tettaphenyporphyrinato)kon( Chloro(2,3,7,8,12,l 3,17,18-octafluoro-5,l 0,15,20teteaphenylporphyrinato)iron(III) Gas chromatography hour(s) 5,10,15,20-tettalds(ttifluoromemyl)po]^hyrin 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin 5,10,15,20-Tetrakis(2,6-dichlorophenyl)porphyrin  FefTPPBrJCl FetTPPF^Cl  2  )  )  Fe(TDCPPF )Cl  3  )  X  p-Polynitro-5,10,15,20-tetealds(2,6-dicUorophenyl)porphyrin 5,10,15,20-Tetramesitylporphyrin 7,8,17,18-Tetrabromo-5,10,15,20-tetramesitylporphyrin 7,8,17,18-Octabromo-5,l 0,15,20-tetramesitylporphyrin 7,8,17,18-Tetrachloro-5,l 0,15,20-tetramesitylporphyrin 5,10,15,20-Tetrakis(4-substituted phenyl)porphyrin 5,10,15,20-Tettakis(perchlorophenyl)porphyrin  XIV  H TPFPP  5,10,15,20-Tetrakis(perfluorophenyl)porphyrin 5,10,15,20-Teteaphenylporphyrin  2  H TPP 2  H TPP(CF ) 2  3  p-Bis(tofluoromethyl)-5,l 0,15,20-teteaphenyporphyrin  2  H TPP(CF ) H TPP(CF ) (CF CF )  7,8,17-Tris(ttifluorornethyl)-5,l 0,15,20-tetraphenyporphyrin 7,8,17-Tris(tofluoromethyl)-l 8-pentafluoroethyl-5,l 0,15,20teteaphenylporphyrin  H TPP(CF,)  7,8,17,18-Tettakis(trifluoromethyl)-5,l 0,15,20tetraphenyporphyrin  2  3  3  2  3  3  2  2  3  4  H TPP(CH )  2  P-Dimethyl-5,10,15,20-tettaphenyporphyrin  H TPP(CH )  3  7,8,17-Trimethyl-5,l 0,15,20-tetraphenyporphyrin  H TPP(CH )  4  2  3  2  3  2  3  7,8,17,18-Tetramethyl-5,l 0,15,20-tetraphenyporphyrin  [H TPP(CH ) ] 4  3  H TPP(CN) H TPP(X) H TPPPh R [H TPP] HMPA HOAc HOMO HR-MS Im z'-Pr 2  2+  4  P-Polycyano-5,10,15,20-tetraphenylporphyrin 2 (or 7)-X substituted 5,10,15,20-tetraphenylporphyrin 2,7,12,17-Tetraphenyl-3,8,l3,18-R substituted porphyrin 5,10,15,20-Tetraphenylporphyrin diprotonated dication Hexamethylphosphoramide Acetic acid  X  2  2  4  7,8,17,18-Tetramethyl-5,l 0,15,20-tetraphenyporphyrin diprotonated dication  4  2+  4  LR-MS LSIMS  Highest unoccupied molecular orbital High resolution mass spectrometry Imidazole z'-Propyl Low resolution mass spectrometry Liquid secondary ion mass spectrometry  LUMO m m  Lowest unoccupied molecular orbital Meta Multiplet  MeCN l-Melm  Acetonitrile 1 (or N)-Methylimidazole Methanol  MeOH (Me Si) NLi rnin 3  lithium bis(trimethylsilyl)amide minute(s)  2  MnCTDCPP^O,),)  P-Polynitro-5,10,15,20-tetalris(2,6-dicMorophenyl)porphyrinato manganese(II)  MnfTDCPPCNO^Cl  Chloro[P-polynitro-5,10,15,20-tetrakis(2,6dichlorophenyl)porphyrinato]manganese(IH)  Mn(TE>CPP)Cl  Chloro[5,l 0,15,20-tetrakis(2,6dichlorophenyl)porphyrinato]manganese(III)  MnCTDCPPBr^Cl  Chloro[2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tettakis(2,6dichlorophenyl)porphyrinato]manganese(III)  Mn(TDCPPF )  2,3,7,8,12,13,17,18-Octafluoro-5,10,15,20-tetrakis(2,6dichlorophenyl)porphyrinatomanganese(Ii) Chloro[2,3,7,8,12,13,17,18-Octafluoro-5,10,15,20-tetrakis(2,6dichlorophenyl)porphyrinato]manganese(IH)  8  Mn(TDCPPF )Cl 8  XV  MnCTPFPPFg)  2,3,7,8,12,13,17,18-Octafluoro-5,l 0,15,20-  Mn(TPPF )  tettalds(perfluorophenyl)porphyrmatomanganese(ir) 2,3,7,8,12,13,17,18-Octafluoro-5,l 0,15,20tetraphenylporphyrinatomanganese (II)  8  Mn(TPPF )Cl 8  MS NADH NADPH N-alumina Ni(TPPBr ) 4  tetraphenylporphyrinatonickel(ir)  NBS NCS NMP NMR  N-Bromosuccinamide N-Chlorosuccinamide N-Methylpyrrolidone Nuclear Magnetic Resonance Ortho Acetate 2,3,7,8,12,13,17,18-Octaethylporphyrin ligand 2,3,7,8,12,13,17,18-Octaethyl-5,l 0,15,20-tetraphenylporphyrinato ligand Oak Ridge thermal ellipsoid plot Triflate or trifluoromethanesulfonate Para Perfluoroiodosylbenzene Benzonitrile Iodosylbenzene Pyridine  0 OAc OEP OETPP ORTEP OTf  P  PFIB PhCN PhIO Py  pyrr-P-H q Rf r.t. s SCE T TBABF TBAP TBAPF TCQ TEAP Temp. TFA THF TLC. TPP UV  Chloto(2,3,7,8,12,13,17,18-octafluoto-5,10,15^0tettaphenylporphyrinato)manganese(III) Mass spectrometry Nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide phosphate Neutral alumina 2,3,12,13,-Tetrabromo-5,10,15,20-  pyrrolic P-protons Quartet (Distance moved by solute) / (distance moved by solvent front) in TLC  4  6  Room temperature Singlet Saturated calomel electrode Temperature Tetrabutylammonium tetrafluoroborate Tetrabutylammonium perchlorate Tetrabutylammonium hexafluorophosphate 2,3,5,6-Tetrachloroquinone Tettaethylammonium perchlorate Temperature Trifluoroacetic acid Tetrahydrofuran Thin layer chromatography 5,10,15,20-Tetraphenylporphyrinato ligand Ultraviolet  XVI  vdW  van der Waals  ZnjTDCPPlNCg,)  (3-Polynitro-5,10,15,20-tetrakis(2,6<dicUorophenyl)porphyrinatozinc(II)  Zn(TDCPP) Zn(TDCPPBr )  5,10,15,20-Tetrakis (2,6-dicUorophenyl)porphyrinatozinc(Ii) 2,3,7,8,12,13,17,18-Octabromo-5,10,15,20-tetrakis(2,6dichlorophenyl)porphyrinatozinc(II) 5,10,15,20-Tettakis(perfluorophenyl)porphyrinatozinc(II) 2,3,7,8,12,13,17,18-Octabromo-5,l 0,15,20tettakis(perfluorophenyl)porphyrinatozinc(II)  8  Zn(TPFPP) Zn(TPFPPBr ) 8  ZnCTPPCCFj)^  ZnCrPP(CF )3(CF CF )) 3  2  Zn(rPP(CF )3) 3  Zn(TPP(CF ) ) 3  4  Zn(TPP) Zn(TPPBr ) Zn(OMPTPP) 4  Zn(TPBC)  3  P-Bis(ttifluoromemyl)-5,10,15,20-tetraphenylporphyrinatozinc(II) 7,8,17-Tris(trifluorornethyl)-l 8-pentafluoroediyl-5,l 0,15,20tettaphenylporphyrinatozinc(Ii) 7,8,17-Tris(trifluoromethyl)-5,l 0,15,20tettaphenylporphyrrnatozinc(Ii) 2,3,12,13-Tetrakis(trifluoromethyl)-5,10,15,20tettaphenylporphyrinatozinc (II) 5,10,15,20-Tettaphenylporphyrinatozinc(II) 2,3,12,13-Tettabromo-5,10,15,20-tetophenyporphyrinatozinc(II) 2,3,7,8,12,13,17,18-Octamethyl-5,l 0,15,20Tetraphenylporphyrinatozinc(II) 2,3,12,13-Tetrahydro-5,l 0,15,20-teteaphenylporphyrinatozinc(II) or ^wo-tetraphenylbacteriochlorinzinc^i)  XVII  NOMENCLATURE The porphyrin core is a cyclic tetrapyrrolic system consisting of 20 carbons, four nitrogens, and two hydrogens. Porphyrins are formally derived from porphin (I) by substitution of some or all of the peripheral positions. The peripheral positions are numbered as shown in la and lb. Ia follows I U P A C (International Union of Pure and Applied Chemistry) and IUB (International  I U P A C numbering system  Fischer numbering system  Union of Biochemistry) nomenclature. 1 There is also an alternate system of nomenclature based on the numbering system shown in lb which was developed by Hans Fischer.^ In modern porphyrin chemistry, the former system of nomenclature (Ia) is adopted to name the large number of synthetic and newly isolated porphyrins systematically. In IUPAC-IUB nomenclature (Ia), positions 1,4,6,9,11,14,16,19 are termed the pyrrolic a-positions, 2,3,7,8,12,13,17,18 are the pyrrolic P-positions and interpyrrolic methine positions 5,10,15,20 are /w.ro-posirions. For example, compound II is named 5,10,15,20-tetraphenylporphyrin or wwo-teteaphenylporphyrin. For the ligand name, porphyrin is changed to porphyrinato or porphinato as 5,10,15,20tetealds(2,6-dicMorophenyl)porphyrinatozinc(ir)  (or  meso-tettakis(2,6-  dichlorophenyl)porphyrinatozinc(ir;) (III). If the pyrrolic p-positions are partially substituted  xviii  and no metal is coordinated to the porphyrin, the pyrrolic oc-carbon o f the pyrrole to w h i c h a hydrogen attached is numbered first. F o r example, c o m p o u n d IV is  7,8,17,18-tetrabromo-  5,10,15,20-tetraphenylporphyrin (or 7,8,17,18-tefjrabromo-^j-o-tettaphenylporphyrin).  When a  metal is coordinated, the pyrrolic a-carbon o f the pyrrole w i t h substituents o n the pyrrolic P-position is numbered first as  2,3,12,13-tetramemyl-5,10,15,20-tettaphenylporphyrinatozinc(II)  (or 2,3,12,13-tetomemyl-^jo-tetraphenylporphyrinatozinc(l])) (V).  XIX  ACKNOWLEDGEMENT  I would like to express my sincere gratitude to Professor David Dolphin for his guidance, patience and encouragement throughout my entire research work. I also wish to take this opportunity to thank members of Dolphin's lab for an enjoyable working environment. Special thanks to Dr. Alison Thompson, Dr. Ethan Sternberg, and Dr. Elizabeth Cheu for proofreading sections of this thesis. Especially, without Dr. Thompson's encouragement, I could not have ' continued my writing.  I would like to thank Professor Brian James for allowing me to use the cyclic voltammetry apparatus in his lab. Thanks also to Dr. Ian Baird for showing me how to use the apparatus. I also would like to thank Dr. Nick Burlinson for taking the time for his advice and helpful discussions about N M R spectroscopy. Thanks also to Ms. Marietta Austria and Ms. Liane Darge for taking nice N M R spectra and for teaching me how to use the N M R machines, to Mr. Peter Borda in the microanalysis lab, Drs. Steve Rettig and Brian Patrick in the X-ray crystallography lab, staff in the Mass Spectrometry lab for their technical support, and to Mr. Brian Ditchburn in the glass shop for making the electrochemical cell.  Thanks also to those people, over the years, who made it an enjoyable experience for me to work in the department of Chemistry at U B C . Special thanks to Dr. Yoshikata Koga for his encouragement and to Drs. Alavi Saman and Mari Kono for their friendship and memorable time in Vancouver. I am also very grateful to Professor Akinori Jyo at Kumamoto University, Japan, who introduced to me a fascinating realm of chemistry.  Last, I would like to thank my wife Miyuki whose smile and patience were essential to completion of this thesis.  1  C H A P T E RI Introduction  A. I n t r o d u c t i o n Hemoproteins perform vital functions in nature. These include molecular oxygen transport and storage-^,  electron  transfer^,  molecular oxygen  activation^,  a n c  j  the  metabolism of organic intermediates. 10-12 "T^Q prosthetic group for most hemoproteins is the protoporphyrin IX Fe complex (Figure 1-1), despite the varying functions of this family of proteins. 13,14 ' p j presence of the protoporporphyrin I X skeleton within various hemoproteins ie  of different function is intriguing and many model studies using synthetic porphyrins have been performed in attempts to identify the mechanism of action of hemoproteins.  1 Figure 1-1. Protoporphyrin I X Fe complex.  Synthetic porphyrins used in model studies of hemoproteins have been prepared using design strategies involving both structural and electronic modifications. Early examples of structurally modified porphyrins used in the model studies of hemoglobins and myoglobins include sterically hindered derivatives!5-17 derivatives.!8-20  s m  w n  ii  e  recent examples have explored non-planar  d y of nonplanar porphyrins is motivated by the hypothesis that fine-  tuning of the porphyrin macrocycle conformation by the protein scaffold of hemoproteins is one way that nature might use to control the functions of prosthetic groups in tetrapyrrole-protein complexes. 18,19,21 -24  Electronically modified porphyrins incorporating strong electron-withdrawing substituents form a class called "electron-deficient  porphyrins" (Figure 1-2).  Strictly speaking, the term  "electron-deficient" refers to compounds for which full octets are not achieved in the Lewis  R  2  R  1  R  2  R = Aryl, C F R = F, CI, Br, N 0 M = 2 H , Zn(II), Fe(III)Cl, Mn(IU)Cl 1  n  2 n + 1  2  2  +  R  2  R  1  R  2  Figure 1-2. Examples of electron-deficient porphyrins.  structure25 (e.g. B H ) . However, the term is arbitrarily used in the literature to refer to 2  6  porphyrins in which the electron density of the macrocycle has been lowered by the presence of strong  electton-withdrawing  substituents. Many  electron-deficient  porphyrins have  been  reported, largely as a result of studies directed towards the determination of the ability of their metal complexes (such as Cr(III), Mn(III), or Fe(III)) to mimic cytochrome P-450.26-28 Cytochrome P-450 enzymes include the protoporphyrin LX Fe(III) complex and are responsible for O  z  activation and oxygen atom transfer (oxygenation) in substrates witiiin biological  systems.^  Biological oxygenation has attracted much attention because the biological systems perform selective oxidation under mild reaction conditions using the abundant oxidant 0  2  and  release water only as a by-product.13,14 Besides P-450, enzymes methane monooxygenase and copper oxygenases such as phenylalanine hydroxylases or tyrosinase are also known as enzymes that catalyze oxygen transfer in substrates utilizing O and model studies have been continued in z  order to understand the mechanisms of the enzymes. 13,14 Elucidation of the mechanisms may potentially aid in the development of useful transition metal catalysts for both fundamental and industrial chemistry.  In fundamental developments  some potentially useful metal complexes that are not  derived from biological systems have also been introduced and studied as oxidation catalysts.29 The most successful examples are Mn(III) complexes of derivatives of salen (Figure 1-3).^,31 The catalytic system with the complexes formed the basis for the development in asymmetric catalytic epoxidation using iodosylbenzene or N a O C l . In industry, some important organic intermediates have been synthesized by catalytic oxidation. For example, oxidation of ethylene to ethylene oxide using A g O or propene to acrolein using B i M o O as the catalysts is the worldwide 2  e  known oxidation processes.32  F i g u r e 1-3. Example of salen Mn(III) complex  4  Oxidation by biological systems is much more sophisticated than such industrial processes in terms of the range of the substrates and the reaction conditions. 13,14 In spite of these advantages,  porphyrins have not been used in industry, although potential commercial  applications of some of the metalloporphyrin systems have been shown.^3 The major reasons for this are probably cosdy preparation and instability of the metalloporphyrins in catalytic oxidations. However, successful development of a system potentially derived from biological systems such as P-450 is still in strong demand for fine, economical, and environmentally friendly chernistry.26,29 Thus, porphyrins have been the major subject in catalytic oxidations for years. In particular, electron-deficiency has been thought to be essential for mimics for P-450 enzymes in order to acquire efficiency and robustness of catalysts34-48  a n c  j fa  e  se  a r c h for a  "perfect" P-450 mimic continues, as described in chapter I of this thesis.  This thesis documents the synthesis and investigation of the properties of some novel electron-deficient porphyrins. In particular, the design, synthesis and electronic properties of p-trifluoromethyl-«?^o-tetraphenylporphyrins will be discussed, in relation to their potential application as cytochrome P-450 rnirnics.  The first part of Chapter I is a review of the development of electron-deficient porphyrins as P-450 mimics, followed by the discussion of design strategies employed for the preparation of novel P-tafluoromediy-^j-o-tetraphenylporphyrins. The remaining part of this chapter is a review of the various analytical methods applicable for the characterization of porphyrins and the evaluation of electron deficiency within the porphyrinogenic macrocycle.  5  B . Metalloporphyrins as cytochrome P-450 model compounds /. Cytochromes P-450 a. Distribution, nomenclature, and structure Cytochromes P-450 (P-450s) are intercellular proteins w i t h molecular weights between 50 and 60 k D . ' > ^  They contain protoporphyrin I X Fe(III) complex (often called "heme") as the  prosthetic group.'  P-450s are widely distributed i n nature from bacteria to mammals.'  It was found that reduction o f the Fe(III) form o f a P-450 enzyme to its Fe(II) state, followed  by coordination o f carbon m o n o x i d e results i n the formation o f an intense absorption  band w i t h a m a x i m u m at about 450 n m i n the optical spectrum.49 T h i s p h e n o m e n o n  led  O m u r a and Sato to name this type o f substance P-450 (a pigment that absorbs light at 450 n m ) -  4 9  Tyrosine  Phenylalanine  Cysteine F i g u r e 1-4. A c t i v e site and h y d r o p h o b i c pocket o f cytochrome P - 4 5 0 . D a r k atoms show hydrogen b o n d i n g (a), h y d r o p h o b i c interaction (b), and coordination sphere o f the heme (c). A d a p t e d f r o m reference 13. cam  To  date,  several  P-450  structures  are known and it has  been  shown  that all  stmcture-determined P-450s share a common protein fold.50 Thus, the heme is buried in the hydrophobic pocket of the protein structure and is coordinated to the thiolate ligand of a terminal cysteine moiety.^, 14,50 The heme-thiolate ligand environment is highly conserved in all P-450s, whatever the exact function of particular enzymes.^ crystal structure of  the  active  site of  Figure 1-4 shows the X-ray  camphor bound cytochrome  P-450 .51 cam  The  protoporphyrin IX Fe(III) complex, the axial thiolate ligand, and the bound camphor as a substrate can been seen within this protein structure.  b. Function and mode of action P-450s play an essential role in the metabolism of endogenous substances (e.g. steroids) and in the detoxification and degradation of substances in animals, plants, and bacteria. 13,14 P-450s catalyze the oxidation of organic substrates by molecular oxygen in cooperation with reducing agents ( N A D H , flavoprotein and iron-sulfur proteins). 14 As shown in equation (1.1a), alkanes are oxidized to alcohols^ and alkenes are oxidized to epoxides (1.1b), by action of P-450 catalysis. Similar catalysis is effected by synthetic Fe(III) and Mn(III) porphyrins. ^3  RCH -H 2  + 0  + 2 H + 2e" +  2  •  RCH -OH 2  X>  + H 0 2  (l.la)  (!' )  Figure 1-5 shows the currendy accepted mode of action of P-450s.l3>14  lb  ca  talyti  c  cycle is initiated by incorporation of a substrate molecule (RH) into the hydrophobic pocket of the protein where the heme-thiolate complex is located. This is accompanied by concomitant loss of a water molecule from the hexa-coordinate Fe(III) complex (T). This step results in a  = [protoporphyrin IX] ' 2  S"-Cys  Figure 1-5. Catalytic cycle of cytochrome P-450.  8  penta-coordinate  complex (2) w i t h high-spin Fe(III). A n electron donated by N A D P H  transferred to the complex via electron-transfer  is  systems such as flavoprotein or iron-sulfur  proteins and reduces (2) to the high-spin penta-coordinate Fe(II) complex (3). T h i s complex subsequendy binds 0  2  to f o r m the low-spin oxy Fe(II) complex (4). T h e F e ( I I ) / 0 moiety is 2  possibly modified to F e ( I I I ) / 0  peroxo Fe(III) complex (6).  2  i n (5). T h e one-electron reduction o f (5) forms the low-spin  T w o protons add to this species and one molecule o f water is  released. T h u s cleavage o f the O - O b o n d results i n the o x o Fe(rV) porphyrin cation radical  (7),  w h i c h reacts w i t h the hydrocarbon substrate to yield an alcohol (or an epoxide w h e n an olefin is incorporated). T h e heme returns to the resting f o r m (1) after the coordination o f water. A s indicated i n Figure 1-5, the cycle can be bypassed (via a "shunt path") by adding oxygen donors ( X - O ) such as iodosylbenzene.  Since P-450s can catalyze the cleavage o f strong C - H  bonds i n hydrocarbons (e.g. 400 k j / m o l for cyclohexane)54 under ambient conditions, chemists have been intrigued to m i m i c the remarkable function o f these enzymes using synthetic metalloporphyrins. It should be noted that n o simple (i.e., non-enzyme) complex o f Fe(III) has been described w h i c h really can use /-alkyl hydroperoxides to m i m i c a monooxygenase (i.e., P-450 like) catalyzed oxidation o f alkanes.55  c. Mechanisms  of hydrocarbon  oxidation  (1) Mechanism  of alkane  hydroxylation  Figure 1-6 shows a general scheme for the cytochrome P-450 catalyzed hydroxylation o f alkanes. A s discussed i n the previous section, the o x o Fe(IV) p o r p h y r i n cation radical is the active species. T h e mechanism is considered to occur first by hydrogen atom abstraction f r o m the substrate followed by rapid transformation o f the metal-bound hydroxy radical to an  intermediate alkyl radical. T h e n combination o f the hydroxy radical w i t h alkyl radical forms the alcohol and the porphyrin returns to the resting s t a t e d  F o r m a t i o n o f the side product is also  s h o w n i n Figure 1-6; escape o f the alkyl radical from the cage o f the transition state, initiates a radical chain autoxidation that produces ketone.56 O  / - T l  *R <*  R  "  ,H  H  Fe(lll)J) + R O H alcohol  escape  •R  -•ROO*  t  O, = porphyrin 71 cation radical R-H = alkane  ketone  F i g u r e 1-6. M e c h a n i s m o f alkane hydroxylation by cytochrome P-450.  (2) Mechanism  Mechanisms  for  hydroxylation.53,57 by cytochrome  epoxidation  by  of alkene  P-450s  epoxidation  are  more  complicated  than  that  for  Figure 1-7 (p. 10) shows a unified mechanism for the epoxidation o f olefins  P-450  complex (1) is formed.  summarized  from  This complex  the  literature.58~61 Firstly, the  then collapses  to  the  carbocation  charge  transfer  complex (2)  by  electrophilic addition o f the oxo Fe(rV) porphyrin 71-cation radical to the olefin. R i n g closure o f (2)  forms the epoxide (3)  and Fe(III) porphyrin. Several side products are also formed. H y d r i d e  and group migration results i n the aldehyde (4) and the ketone (5) reaction  Fe(III)  porphyrin is generated. N - A l k y l a t i o n to give  formation to give (7)  respectively. In each side(6)  and  iron-carbon  can also occur. A l t h o u g h the major product is always the epoxide (3),  bond the  10  extent of each of the alternative substrates.53  ^  pathways depends on the individual porphyrins and  R  R  R  R R  +  6  o  epoxidation  R  o  R O R R  H migration  •  R  o  R  O  Fe(lll)  R -+ R migration  R  R  O  R F e - C bond formation  R  F i g u r e 1-7. Mechanism of the oxidation of olefins by cytochrome P-450 or metalloporphyrins.  11 2. Synthetic metalloporphyrins as P-450 mimics a. Structures ofporphyrins that appear in this section In order to proceed, the major porphyrins that appear i n section B.2.b are shown i n Figure 1-8.  Section B.2.b.  documents  the  investigation  of  synthetic  porphyrins  and  metalloporphyrins as P-450 mimics.  Porphyrin  R  M(TPP) M(TMP) M(TPFPP)  phenyl mesityl perfluorophenyl 2,6-dichlorophenyl perchlorophenyl phenyl perfluorophenyl 2,6-dichlorophenyl 2,6-dichlorophenyl perchlorophenyl phenyl 2,6-dichlorophenyl perfluorophenyl 2,6-dichlorophenyl C F  (2) (3) (4)  M(TDCPP) M(TPCPP) MfrPPBrg) M(TPFPPBrg) MfTDCPPBrg)  (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)  MfTDCPPCL) M(TPCPPC1 ) M(TPPF ) M(TDCPPF ) MCTPFPPFs) 8  8  8  MCTDCPPCNO^flS) (16) M(C F ) P n  7 n + 1  R  i r )  4  H H H H H Br Br Br CI CI F F F N0  ^ n 2n+l 1  (a) M = 2 H ; (b) M = Zn(II); (c) M = C u ( H ) ; (d) M = Fe(III)Cl; (e) M = Fe(II); (f) M = M n ( I I I ) C l ; (g) M = Mn(II) ** Catalogue for R aryl groups 1  R  1  phenyl  Pmeso  R H  mesityl perfluorophenyl 2,6-dichlorophenyl  CH F CI  perchlorophenyl  CI  PmeSO'. meso-rposixion  R  3  3  4  R  5  H  H  H F H  CH F H  CI  CI  3  o f porphyrin  Figure 1-8. Porphyrins used i n P-450 m o d e l studies.  2  or H  2  H  12  b. Synthetic methodsfor the majorplayers in the early development of PA 50 mimics (1) Condensation of pyrrole with arylaldehydes Porphyrins used in early P-450 model studies were symmetric and easy to prepare,-^ via the condensation of equimolar quantities of pyrrole (or a 3,4-disubstituted pyrrole) and an arylaldehyde, followed by oxidation. 62-67  This strategy was originally used by Rothmund, who reacted pyrrole and benzaldehyde in pyridine in a sealed flask at 150 °C for 24 h to yield «?MO-tetraphenylporphyrin (H TPP) (2a) in 2  about 3% yield.°2  The yield was improved up to 40 % by Adler, Longo and coworkers who  carried out the reaction in propionic acid or acetic acid open  to the air (Scheme 1-1  Path y4).63,64 Reasoning that porphyrin is formed via the formation of porphyrinogen (17)65,  o  Path/*  C  N  II  Propionic or acetic acid/air  O  Path B  H  +  S c h e m e 1-1. Synthesis of wwo-tetraarylporphyrins.  Lindsey et al. revised the method devised by Rothmund, and Adler-Longo.66 method (Scheme 1-1 Path 13)66 j  s  a  The Iindsey  two-step one-pot procedure whereby the pyrrole and the  13  aldehyde are condensed with a catalytic amount of acid under anaerobic conditions to form porphyrinogen, which is subsequently oxidized to porphyrin by an oxidant such as 2,3,5,6tetrachloro-quinone (TCQ) or 2,3-clicMoro-5,6-dicyano-quinone (DDQ). The initial reaction is carried out in a chlorinated solvent such as C H C 1 or CHC1 at room temperature for about 1 h 2  2  3  before the oxidant is added. One drawback relating to this method is the rather low reaction concentrations (as low as 10" M ) . 2  allowed  the  synthesis  6 6  However, the mild reaction conditions of this method have WOT-tetramesitylporphyrin (H TMP) (3a),  of  2  (perfluorophenyl)porphyrin (H TPFPP) (4a),  «?&ro-tetrakis-  ^j-o-tetralds(2,6-dicruorophenyl)porphyrin  2  ( H T D C P P ) (5a), and OTWo-tettaltis(perchlorophenyl)porphyrin (H TPCPP) (6a) (see Figure 1-8, 2  2  p. 11)67  w  n  0  s  methods. 63  e  syntheses and isolation had not been possible by the Rothmund or Adler-Longo  64  Metallation of porphyrins to give metalloporphyrins is generally achieved by the reaction of porphyrin with a metal salt under various conditions. ^> ^ Thus, access to Fe(III) or Mn(III) 6  6  complexes of porphyrins 2-6 that were important for P-450 model studies became possible.  (2) /3-Perchlorinated andperbrominated meso-arylporphyrins (3-Octachloro  and P-octabromo-tettaarylporphyrins  cannot  be  synthesized  by  condensation of 3,4-dichloro- or 3,4-dibromopyrrole and aryl aldehydes due to the difficulty incurred in preparation of the requisite  3,4-dihalopyrroles.^^  Direct chlorination and  bromination of the P-pyrrolic positions of porphyrins have been reported to be extremely efficient to effect structural and electronic modifications of tetta-arylporphyrins (Scheme 1-2).^0 p-Chlorination^l ^ and bromination ,44,71,75-77 -  using  various  4  cMorinating  34  D  f metallated porphyrins can be achieved  (Cl , N-chlorosuccinamide 2  (NCS))  and brominating  (Br , 2  14  N-bromosuccinamide (NBS)) reagents in numerous solvents (CHC1 , CC1 , C H C 1 and MeOH). 3  Metallation  of  porphyrins prior  to  this  reaction  is  necessary  4  in  2  2  4  order to  complete  P-halogenation.^O As shown in Table 1-1, yields for P-halogenation are generally high. Due to the ease of synthesis, and their unique characteristics, halogenated porphyrins have been extensively studied as P-450 mimics.  X = Br and CI S c h e m e 1-2. P-Halogenation of OTWo-tetraarylporphyrin. A r = phenyl, mesityl, perfluorophenyl, 2,6-dichlorophenyl, perchlorophenyl, M = Ni(II), Cu(II), Zn(II), Mn(III)Cl and Fe(III)Cl.  T a b l e 1-1. Yields of typical P-perhalogenation reactions. Starting porphyrin  Yield (%)  P-halogenated  Cu(TPP)  (2c)  Cu(TPPBr )  Zn(TPFPP)  (4b)  Zn(TPFPPBr )  (8b)  Zn(TDCPP)  (5b)  Zn(TDCPPBr )  (9b)  (6d)  Fe(TPCPPCl )Cl  Fe(TPCPP)Cl  (7c)  8  8  8  8  (lid)  75 6 0 8 0 71 85  Reference  75 78 34 73  c. Early development of P-450 mimics In 1979 Groves et al. investigated the oxidation of several hydrocarbons using a synthetic porphyrin, Fe(TPP)Cl (2d)  (Figure 1-8, p.11), as catalyst and iodosylbenzene (PhIO) as oxidant  15  and demonstrated the P-450-like catalytic activity of the metalloporphyrin via a "shunt path" mechanism.79 For example, cyclohexene and cyclohexane were converted into cyclohexene oxide (55 %) and cyclohexanol (8 %) respectively.^ This original work pioneered model studies towards the investigation of other metal complexes of T P P (such as 1^(111)80,81^ Cr(III)82  r  Ru(VI)83) the effect of basic axial ligands84-87 the effect of oxygen donors88-91  2  5 Q  )  ;  5 a n c  j  u  s  e  Q  f 0  as oxidant in the presence of a coreductant (such as N a B H or Zn(Hg) for Fe(III/II) reduction 4  to mimic the natural P-450 oxidation process.92-95  Although the TPP-based catalysts (first-  generation catalysts) were relatively effective mimics of P-450 reactions, there was a problem in that  their  catalytic  activity  metalloporphyrins.26-28 occur readily at the  meso  was  rapidly  decreased  by  oxidative  degradation  of  the  Since the oxidative degradation of metalloporphyrins is known to ring p o s i t i o n ^ ^ ^ protection of this position became an important goal  for the improvement of catalytic activity. Two approaches were developed for the protection of the ^jo-positions; protection of the  meso-X50%\Xuor\s>  from the oxidant by bulky adjacent groups-^  and the introduction of strong electton-withdrawing groups, which is also important to obtain an active metal center.99  Groves et al. showed that Fe(TMP)Cl (3d)  (Figure 1-8, p.11) can resist, to some extent,  oxidative degradation due to the steric effect of bulky mesityl groups at the wwo-positions.98 Also, Chang and Ebina carried out the epoxidation of cyclohexene with an electron-deficient, Fe(TPFPP)Cl (4d) yield.99  (Figure 1-8) and PhIO as oxidant and obtained cyclohexene oxide in 95 %  When both steric bulk at the Wcvo-positions and electton-withdrawing groups are  combined witiiin a wwo-arylporphyrin, catalytic behavior is improved tremendously.  In 1984,  Traylor et al. reported a turnover (mole of product/mole of catalyst) of 10,000 and 85 % yield in  16  the  epoxidation  of  norbornene  using  pentafluoroiodosylbenzene (PFIB) as oxidant.  Fe(TDCPP)Cl (5d) (Figure 1-8)  and  These improved metalloporphyrins, 3d, 4d,  and 5d, are called second-generation catalysts.26,28  Although the second-generation catalysts effectively catalyze the epoxidation of alkenes, the oxidative degradation of these Fe(III) porphyrins is still noticeably severe during alkane hydroxylation.28  J  N  a  attempt to synthesize more robust catalysts, perhalogenation at the  n  p-pyrrolic positions was performed to give third-generation catalysts. The first third-generation catalyst, Fe(TDCPPBr )Cl (9d) (Figure 1-8) was reported by Traylor and Tsuchiya in 1987. 8  1990,  three  more  third-generation  catalysts,  34  In  FeCTPFPPBr^Cl (8d) (Figure 1-8), 44  Fe(TDCPPCl )Cl(10d) (Figurel-8) and FeCTPCPPCkJCl (lid) (Figure 1-8) were reported. 73  73  8  These metalloporphyrins are much more electron-deficient compared to the first and the second generations, as a result of P-Br and CI substituents. This can be appreciated by consideration of the Fe(III/II) redox potentials of the iron porphyrins. For example, the Fe(III/II) redox potential of l i d is positively shifted by 0.64 V from that of Fe(TPP)Cl (2d) (Figure 1-8).  73  The  effects of electron-withdrawing substituents were further investigated due to the ready synthesis of these highly electron-deficient porphyrins (section B.2.a.(2). in this chapter) and resulting increase in catalytic activity.26-28  d. Electron-withdrawing effects on catalytic activities Before we move into this subject, we should keep in mind that investigations of catalytic oxidation are normally conducted in the presence of excess substrate. Therefore, for example, oxidation of alkane is forced to cease at the formation of alcohol, and alcohol to ketone by catalysis is not a competing reaction. We should also keep in mind that the detailed reaction  17  conditions such as reaction media, mole ratio of reactants, or oxidants are different from one report to another, which makes  direct comparison of product yields between different  experiments very difficult. Thus, the comparison of the catalysts should be done within experiments performed under the same conditions.  Traylor et al. studied Fe(TDCPPBr )Cl (9d) 8  the  hydroxylation  of  cyclohexane  (Figure 1-8) and PFIB as oxidant. 101  and norbornane  using  The yield of cyclohexanol was  93% based on the consumed PFIB with a high ratio of alcohol to ketone (37/1). The hydroxylation of cyclohexane using Fe(TPP)Cl (2d)  (Figure 1-8) and PhIO gave an alcohol to  ketone ratio of 12/1.52 As explained in section B.l.c.(l)., formation of the ketone side product results from the escape of the alkyl radical from the cage of the transition state.-^  In other  words, the oxo Fe(TV) porphyrin 7t-cation radical obtained from electron-deficient 9d is more reactive than that formed from 2d and thus gives the alkyl radical less opportunity to escape from the cage. 101 The hydroxylation of norbornane with 9d and PFIB gave the corresponding alcohol in 82 % yield with much higher selectivity for alcohol (alcohol to ketone > 99/1).101 Traylor et al. also investigated the reactivity of the oxo Fe(rV) porphyrin 7t-cation radical towards  the bond cleavage of / - B u O O - H and alkene epoxidation (Figure 1-9). 102,103 j  t  l  s  necessary to  prevent the side reaction (Path B) in order to obtain a high yield of epoxide (Path A) using A B u O O H as an oxygen donor (Figure 1-9). The value o£k /k , A  where k = rate of epoxidation  B  A  and k = rate of /-BuOO' formation, indicates selectivity for the epoxidation (Path A). When B  Fe(TMP)Cl (3d)  (Figure 1-8)  andABuOOH, while k /k A  B  was used  as a catalyst,  > 1 with Fe(TPFPP)Cl (4d)  k /k A  B  = 0.01 for cyclic alkenes  (Figure 1-8) and F e f T D C P P B r ^ C l  (9d)  18  (Figure 1-8)  as  the  strength  of  the  electron-withclrawing  substituents was  increased. 103  M o r e o v e r , the rate o f metalloporphyrin destruction was also decreased. 102 (Path A) alkene CI  O \  epoxide  PPIR  QFe(lll)J) 7^)  >• (  Fe(IV)  (Path S) f-BuOOH  = porphyrin dianion  f-BuOO •  i-a  = porphyrin 71-cation radical  Figure 1-9. R e a c t i o n o f o x o F e ( I V ) p o r p h y r i n 7t-cation radical w i t h alkene and ^-BuOOH.  Bartoli et al.  compared  the effectiveness  (Figure 1-8) i n the hydroxylation o f  o f Fe(III) porphyrin catalysts (5d  heptane using P h I O . 4 0  and  lOd)  T h e total yields (heptanols +  heptanones) by 5d, and lOd were 36 and 80 % , respectively. T h e regioselectivities for  the  position o f hydroxylation (2, 3, and 4 positions o f heptane) were 58:30:12 (positions 2:3:4) for 5d and 43:40:16 for lOd. H i g h e r reactivity o f the o x o Fe(TV) p o r p h y r i n 7T.-cation radical o f the more electron-deficient  metalloporphyrin  10b  leads  to  lower  regioselectivity  of  hydroxylation.  Carrier et al. showed that hydroxylation o f anisole w i t h M n ( T D C P P ) C l (5f) (Figure 1-8) H O 2  z  and  as an oxygen d o n o r gives ^wra-hydroxyanisole w i t h 95 % regioselectivity and i n 50 % yield,  while w i t h M n ( T D C P P B r ) C l (91) (Figure 1-8) 75 % regioselectivity occurs and 70 % yield o f 8  hydroxyanisole obtained.^  0  These results can similarly be explained by the higher reactivity o f  the third-generation catalyst 9f compared to the more electron rich 5f.  Ellis and L y o n s reported  the  oxidation o f isobutane using Fe(III)  molecular oxygen without the requirement for a coreductant.44,45  porphyrins  and  F e ( T P F P P B r ) C l (8d) 8  (Figure 1-8) catalyzed the oxidation o f isobutane to /-butanol more efficiently than the second-  19  generation  F e ( T P F P P ) C l (4d)  catalyst  turnover.44,45 - p h  e u  s  e  Q  f  (Figure 1-8)  i n terms  o f the  product  yield  and  resulted i n the formation o f Abutanol w i t h greater than 90 %  selectivity a n d a total turnover o f 12,000. T h e catalytic activity o f 8d was maintained for 74 h . Table 1-2 shows the Fe(III)/(H) redox potentials and catalytic activities (turnovers) observed for the oxidation o f isobutane w i t h Fe(III) porphyrins o f different generations, a n d electronic properties, under identical condition.45 Electron-deficiency is reflected b y the positively shifted Fe(Iir)/(II) redox potentials o f the second and the third-generation catalysts, (4d  and  8d)  respectively. It was believed that catalytic activity could be mapped b y an increase o f the Fe(III)/ (II) redox potentials, highlighting the inherent relationship between electron-deficiency and catalytic activity o f the metaUoporphyrin.45  T a b l e 1-2. Relationship between catalyst i r o n redox potentials and activities/ Catalyst  Fe(III)/(II),E  1/2  (V)  Total turnovers  b  -0.221 +0.07 +0.19  Fe(rPP)Cl (2d) F e ( T P F P P ) C l (4d) F e C T P F P P B r ^ C l (8d)  0  0 1160 1800  Ref.45. C y c l i c voltammetry i n C H C 1 vs. S C E . Supporting electrolyte; tetrabutylammonium perchlorate ( T B A P ) . M o l e o f p r o d u c t / m o l e o f catalyst for the oxidation o f isobutane i n benzene at 60°C.  a  b  2  2  c  Ellis and L y o n s proposed a mechanism to rationalize the oxidation o f isobutane by the catalyst a n d 0  2  alone (Figure 1-10).44,45 ' p i  u s  mechanism includes three key assumptions; (i) due  to the positively shifted i r o n redox potential, Fe(II) is produced by homolytic cleavage o f F e ( f f l ) - C l (1), (ii) after  the  successful  binding o f 0  2  to give  (2), formation  o f the  u—peroxodimer (3) a n d then the catalytically active o x o Fe(TV) p o r p h y r i n (4) occurs w h i c h then oxidizes the substrate, via H abstraction and a ' O H rebound mechanism (6), (iii) due to the bulky  20  F i g u r e 1-10. Catalytic cycle for isobutane hydroxylation by 0 by Ellis and Lyons. Reference 44 and 45.  2  and 8d proposed  21  and severely distorted porphyrin structure, formation of the ^-oxodimer (5), which is catalytically inactive^ 04,105^ i suppressed. The experimental data obtained, and the mechanism described by s  Ellis and Lyons, was extremely interesting since it involves the least expensive oxygen atom source, 0 , as the oxidant. 106 2  In fact, subsequent studies revealed that Fe^TPFPPBrg) (8e)  (Figure 1-8) is extremely  stable and binding of oxygen to this species is unlikely. 104,107 Grinstaff etal.^^ showed that an alternative radical-chain autoxidation mechanism is operative in the experiments carried out by Ellis and Lyons.44  Additionally, Bottcher et al. showed that molecular modeling based on a  radical-chain autoxidation mechanism fit well with the catalytic activities of 8d (Figure 1-8) in alkane hydroxylation using O .104 The role of 8d in a radical-autoxidation mechanism was 2  thought to involve the decomposition of alkyl hydroperoxide. 104,107 j deficient porphyrin 8d  n o  m  e  r words, electron-  is a very efficient catalyst for hydroperoxide decomposition and,  therefore, oxidation.  In summary, metalloporphyrins substituted with bulky and/or electron-withdrawing substituents are much more efficient and robust catalyst than unsubstituted metalloporphyrins. Investigations regarding the relationship between electron-deficiency and catalytic activity or robustness is still an active area in P-450 mimic research.42,43,47,48 The next section of this thesis will further discuss the effects of the introduction of electron-witlidrawing substituents onto the periphery of metalloporphyrin macrocycles.  22  e. Newer generation of electron-deficient porphyrins (1) (5-Verfluoro-meso-tetraarylporphyrins (a)  Synthesis  Direct fluorination of Zn(TPFPP) (4b) (Figure 1-8) using C o F reported in 1989^8 itreproducible.28  D U  t  this method  Recent successful  has  3  or A g F in C H C 1 2  2  was  not been utilized by others because it is  synthesis of 3,4-difluoropyrrolel09  has enabled  the  synthesis of (3-octafluoro-tetraarylporphyrins (12-14) (Figure 1-8) by condensation of the 3,4difluoropyrrole and aryl aldehydes. 36  Mn(TPPF ) (12g), 8  41  >  43  M n C T D C P P F ^ C l (13f),  Metallation using Mn(II) gave M n f T P P F ^ C l (12i), and MnfTDCPPFg)  (13g).  MnfTPFPPFg) (14g)  (Figure 1-8) was the only manganese species obtainable for 14 due to the strong electronwithdrawing effect of the substituents. Normally Mn(III) is the most stable oxidation state in M n porphyrin chemistry but Mn(II) porphyrin can be isolated as a stable compound due to the high electron-deficiency of porphyrin ligands 13 and 1 4 .  43  Fe(III) porphyrins of 12-14 were also  synthesized. ^ 4  (b) R o b u s t n e s s  test  Porhiel et al. evaluated the robustness of iron and manganese complexes towards oxidative degradation of 12-14 by observing the decrease in Soret absorption (see section D.l.a. for a description of the use of UV-vis absorption spectroscopy for the study of porphyrins and metalloporphyrins) in the presence of oxidants PhIO and H 0 in the absence of substrate . 42,4-3 2  2  Oxidative degradation of the metalloporphyrins would inevitably result in a decrease in the intensities of the UV-visible absorption band. Thus, UV-visible spectroscopy provides an ideal method for determination of the robustness to oxidation of the potential catalysts.  23  FeCTPPFgJCl (12d), less  stable  to  F e f T D C P P F ^ C l (13d) and FefTPFPPF^Cl (14d) (Figure 1-8)  oxidation  than  the  Fe(TDCPP)Cl (5d) (Figure l-8).42  second-generation  catalysts  were  Fe(TPFPP)Cl (4d)  Interestingly, 14d, which is the most  and  electron-deficient  species based on the porphyrin ring redox potential of zinc derivatives (the first ring oxidation potential for ZnfTPFPPFg) (14b) (Figure 1-8), 1.70 V vs. S C E ; for Zn(TPP) (2b) (Figure 1-8), 0.80 V vs. S C E in C H C 1 ) 6 3  2  comparing  12d-14d,  Mn(TPPF ) (12g), 8  2  4d,  ;  w  and  a  s  the least robust towards oxidative degradation when  5d.42  MntTDCPPF^Cl  The  (13f),  manganese  Mn(TDCPPF ) 8  complexes (13g)  Mn(TPPF )Cl (121), 8  and Mn(TPFPPF ) (14g) g  (Figure 1-8) with PhIO as oxidant showed similar stability towards oxdative degradation to that of Mn(TPFPP)Cl (4f) and Mn(TDCPP)Cl (5f) (Figure 1-8).  With H 0 2  2  as oxidant, 12f, g and  13f, g were less stable than 2f, 4f and 5f. Metalloporphyrin 14g remained as the Mn(II) species even in the presence of H 0 , suffering no oxidation.42 2  2  It is reasonable to expect that a higher ring oxidation potential of a porphyrin ligand would be advantageous to increase the stability of the porphyrin catalyst to oxidation but these results suggest that the presence of strong electron-withdrawing groups is not always accompanied by robustness and high activity of the corresponding catalyst.  (c) O x i d a t i o n studies Hydroxylation of cyclohexane and epoxidation of cyclooctene with iron  complexes  12d - 14d and PhIO in C H C 1 gave similar results to those found using 4d and 5d as catalysts ie 2  2  10-30 turnovers/1.5 h for both substrates. 14d and H 0 2  2  However, the oxidation of cyclooctene with 12d —  was found to be less successful (3-4 turnovers) than with 4d and 5d (10-60  turnovers).42 These results concur with the results of the robustness test. Interestingly, 14d was  24  the only c o m p o u n d that catalyzed the hydroxylation o f benzene to phenol, w h i c h is more difficult than hydroxylation o f an alkane i n terms o f the C - H b o n d cleavage ( C - H b o n d energy is 400 k j / m o i for cyclohexane and 464 k j / m o l for b e n z e n e ) ^ w i t h 2 turnovers i n the presence o f H 0 . 4 2 T h i s may i m p l y that the oxo Fe(TV) porphyrin 7t-cation radical formed from 14d is 2  2  reactive towards the strong C - H b o n d o f benzene, but oxidative destruction o f itself is extremely competitive due to its high reactivity.  Cyclohexane oxidation w i t h manganese complexes 13f, g and 14g, w h i c h feature b o t h electton-withdrawing groups at the /#£fo-positions and electron-withdrawing fluorine substituents at all o f the P-positions, and P h I O i n C H C 1 2  2  resulted i n 10 - 30 % yield (cyclohexanol +  cyclohexanone). There was little improvement from the oxidation o f cyclohexane w i t h 4f and 5f, w h i c h do not have P-substituents. T h e oxidation o f cyclooctene w i t h 13f, g and 14g and H 0 2  2  in  C H C 1 / C H C N ( 1 / 1 ) d i d not give epoxide, while 4f and 5f yielded epoxide i n 69 % and >98 % , 2  2  3  respectively.  (d) C o n c l u s i o n F r o m the results shown above, P o r h i e l et al. concluded that instability towards oxidative degradation and l o w catalytic activities o f p-octafluoro-wwo-tettarylporphyrins might arise from the  combination  of  catalyst  susceptibility  to  nucleophilic  attack,  potential  oxidative  decomposition o f the metal o x o species, and extremely stable l o w oxidation metal state (e.g.  Mn(ir)).42,43  Evidently, the introduction o f strong and plentiful electton-withdrawing groups  per se does not result i n effective P-450 m i m i c catalysts.  25  (2) B-Nitro-meso4etrakis(2,6-dichlorophenyl)porphyrins  (a)  Synthesis  Ozette et al. have reported the syntheses of fj-polynitroporphyrins and the positively shifted reduction potential of Zn(II), Ni(II)37,110  a n (  j M n ( I I ) l l l complexes of $-mSio-meso-  tetrakis(2,6-dichlorophenyl)porphyrins (15). The reaction scheme for the synthesis of 15 is shown in Figure 1-11. Titration of Zn(TDCPP) (5b)  with red fuming  (1:0.12:0.06) selectively produces Z n ^ D C P P ^ O ^ J (15b)  HNOJ-CFJSOJH-^SO^O  according to the amount of nitrating  agent used. The yields are 78, 90, 86, 93, 80, 95, 90, and 50 % for 15b with x = 1,2,3,4,5,6,7, and 8 respectively. free-base  15a,  complexes.  The Zn(II) complexes, 15b (x = 1 - 8) can be demetallated with acid to obtain  37  which is subsequendy  M n complexes  MnfTDCPPfNO^Cl  reacted with manganese(Ii) acetate  bearing one  to  four  P-nitro groups  can be  to  obtain M n  converted  to  (15£ x = 1 - 3) by treatment with gaseous HC1 in aerobic CH C1 . For 2  2  x = 5, the treatment with HC1 leads to a mixture of M n f T O C P P f N O ^ C l  (15f: x = 5) and  M n ( T D C P P ( N 0 ) ) (15g: x = 5). For x = 6, 7, and 8, it is only possible  to isolate the  2  x  M n t T D C P P t N C g j (15g: x = 6 - 8 ) .  47  (b) O x i d a t i o n studies The  electron-withdrawing effects observed as a result of nitration are remarkable.  Compound 15b (x=8, +0.155 V vs. S C E ) gives the highest reported first reduction potential of 1.44 V , positively shifted from 5b (-1.28 V vs. S C E ) . H 0  Manganese complexes of compounds  15f and g exhibit a remarkably wide span of Mn(IIi)/Mn(II) redox potentials that range from — 0.29 to +1.15 V (vs. S C E in CFLCkJ .47,111  26  Ar=  v(N0 )x 2  N  N Ar H  Zn(TDCPP)  +  Zn(TDCPP(N0 ) ) X = 1 -8 15b 2  5b  (N0 ) 2  x  x  For x = 1 - 4: Mn(TDCPP(N0 ) )CI 15f(x = 1 -4) 2  i) Mn(OAc) ii) HCI gas in CH CI 2  Ar H TDCPP(N0 ) 2  2  X = 1 -8  x  2  2  x  For x = 5 : Mn(TDCPP(N0 ) )CI and Mn(TDCPP(N0 ) ) 1 5 f o r l 5 g (x = 5) 2  x  2  x  For x = 6 - 8: Mn(TDCPP(N0 ) ) 15g (x = 6 - 8) 2  x  15a  Figure 1-11. Synthesis of P-polynitto-/»wo-tetakis(2,6-dichlorophenyl)porphyrins.  27  Bartoli et al. studied the hydroxylation of anisole and naphthalene using manganese complexes of 15 and H 0 2  between  the  catalytic  2  as an oxygen transfer reagent and found interesting relationships  activity  and the  electron-deficiency  of  the metalloporphyrins.^  7  Comparison of M n f T D C P P t N O ^ C l (15f: x = 1 - 4), M n f T D C P P ^ O , ) ^ (15g: x = 5 - 8) and Mn(TDCPP)Cl (5f) (Figure 1-11) as catalysts showed that 15f (x = 1), 15f (x = 2), 15f (x = 3), and 15f (x = 4) gave 97, 96, 98, and 79 % yield respectively for the hydroxylation of anisole and 79, 83, 69, and 49 % yield respectively for the hydroxylation of naphthalene.^"  7  Regioselectivity  decreased as the number of nitro groups increased; for the hydroxylation of anisole, the product ratio of (/wra-hydroxylated anisole/o^o-hydroxylated anisole) was 13, 11, and 9 and for the naphthalene, (a-hydroxylated naphthalene/(5-hydroxylated naphthalene) was 10, 9, and 8 with the catalysts 15f (x = 1), 15f (x = 2), and 15f (x = 3) respectively.  Both the yield and the  regioselectivity for the hydroxylation of anisole by 15f (x = 1) were improved compared to the results obtained with 5f.  Interestingly, the total yield of product obtained from the hydroxylation of anisole was observed to be low when catalysts containing more than five nitro groups on the p-pyrrolic positions were used, despite the increased electron-deficiency of the macrocycle. As an extreme example, 15g (x=8) gave the oxidation products in less than 2 % yield for both anisole and naphthalene hydroxylation.^  7  (c) C o n c l u s i o n P-Nitrated Mn(IIi)-porphyrins show increased catalytic activity compared to the second generation  catalyst,  Mn(TDCPP)Cl (5f) (Figure 1-8).  However,  the  number  of  P-nitro  substituents must be carefully controlled since over-nitration (more than five nitro substituents)  28  results in a severe loss of catalytic activity. This may be due to the stability and catalytic inactivity of the Mn(II) oxidation state under the influence of highly electron-deficient porphyrins.  (3) meso-Tetrakis(perfluoroalkjl)porphyrins (a) Synthesis and o x i d a t i o n studies There  are  three  methods  to  synthesize  »wo-tettaltis(perfluoroalkyl)porphyrins  (Figure 1-12). Two methods involve the synthesis of perfluoro-l-(2-pyrroryl)-l-alcohol (18), which can be synthesized from the reaction of pyrrole and perfluoroalkyl aldehyde hydrate (Path A) or the reaction of pyrrole and perfluoroacyl chloride (Path B). Pyrrole 18 undergoes addition and cyclization in dry benzene to form porphyrinogen 19 that is oxidized to the porphyrin  16a  with  D D Q . The  yield  obtained  by  DiMagno et al.  (OTWo-tetrakis(heptafluoropropyl)porphyrin) was 37 % based on 1 8 .  3 8  for  16a (n = 3)  The yields obtained by  Golltf/'tf/. by this method for 16a (n = 1) (^j-o-tettalds(tjifluorometFiyl)porphyrin), 16a (n = 3), and 16a (n = 7) (wwo-tetj:alds(pentedecafluoroheptyl)porphyrin) were 16, 38, and 34 % based on 18 respectively. ^ Alternately Wijesekera reported the synthesis of 16 via dipyrromethane 20 in 3  which the yields for 16a (n = 1) and 16a (n = 3) were 6 and 9 % respectively based on 20.112 The strong electron-withdrawing effect due to the perfluoroalkyl groups is reflected in the first oxidation and reduction potentials of the Z n porphyrin. For example Z n porphyrin 16b (n = 3) has +1.46 V (the first oxidation) and -0.72 V (the first reduction) vs. S C E , which are greatly changed from +0.79 V and -1.39 V vs. S C E for Zn(TPP) (2b) (Figure 1-8) in P h C N .  There are only a few studies regarding Fe(II) and Fe(III) complexes of  I6H  3  3 8  and catalytic  oxidation using these Fe complexes.48 According to Moore et al., the catalytic activity of Fe(II) complex  of  16 (16e)  is  the  same  as  the  second  and the  third generation  catalysts  29  H  0  >  2  H +  O N H  Cn^2n+1  Path A  °Y  Path B  .  C I  O  C F2n+1  N H  n  1 THF/triethylamine 2.NaBH 4  C H /molecular sieves, 4A 6  6  -4H Q 2  K  . CnF2n+1 n r  C F n 1 n  F  2n+lC  n  ff  2  F  +  H  DDQ  2 n + 1  C "  /  n  C F n  2 n  >  Metallation  16b: M = Zn(ll) 16e: M = Fe(ll)  O THF/HCI H  H  20  N H  HO^OH  o r  H0^J0CH  Path C C F2n+1 n  Cn^n+I  F i g u r e 1-12. Synthesis of wwo-tetrakis(perfluoroalkyl)porphyrins.  3  +i  30  Fe(TPFPP) (4e)  and Fe(TPFPPBr ) (8e) 8  (Figure 1-8) in hydroxylation of isobutane and there was  a slight improvement of robustness of 16e whether  Fe(II  or  III) (or  other  from that of 4e and 8e.48 In order to conclude  metal  such  as  Cr  or  Mn)  complexes  of  wwo-tetraltis(perfluoroalkyl)porphyrins are effective as P-450 model compounds, more detailed studies will be required.  3. Design conceptfor a new P-450 mimic a. Basic concept The basic concept for a new P-450 mimic was constructed based on the previous studies of P-450 rnimics using electron-deficient  porphyrins.  It has been shown that electron-  withdrawing substituents are mandatory to protect the porphyrin macrocycle from oxidative degradation and to enhance the reactivity of the oxo iron intermediate. However, as seen in the oxidation studies using p-perfluoro-wwo-tetraarylporphyrins ^j o-tetralds(2,6-dicUorophenyl)porphyrins (15) -  ( 1 2 1 4 ) (Figure 1-8) and P-polynitro-  (Figure 1-11), extremely  strong or plentiful  electron-withdrawing groups may deactivate the catalysts and/or facilitate decomposition of the macrocycle by nucleophilic attack. Therefore, a moderate electronic effect would be ideal. Steric effects should also be considered as an important factor, in order to increase the robustness of the catalysts. Introduction of bulky substituents onto the porphyrin macrocycle prevents unnecessary contact of the porphyrin core with oxidants (oxo metal intermediate, PhIO, R O O H , etc) and prevents the formation ofthe p-oxodimer which is catalytically inactive. 104,105  As a bulky and electron-withdrawing substituent, the trifluoromethyl group (-CF ) is a 3  good choice. Perfluoroalkyl groups have already been introduced on the OTW0-position 8,39 3  indeed on the P-pyrrolic positionsll4-U8  Q  anc  j  f porphyrins. However, there have been no literature  31  reports o f the introduction o f trifluoromethyl (or perfluoroalkyl) groups o n the (3-pyrrolic positions o f wwo-tetraarylporphyrins as far as the author is aware. A s ^wo-tetraarylporphyrins have been well studied as P-450 mimics, the synthesis and characterization o f P~trifluoromethyl (or perfluoroalkyl)-/W£f0-tettaarylporphyrins may provide potentially new and i m p r o v e d catalysts.  b. Potential advantages of trifluoromethyl substituents A c c o r d i n g to the H a m m e t t equation,! 19 electton-withdrawing or electron-releasing ability o f substituents can be expressed as a quantitative measure called substituent constant value (a). Some substituent constant values are summarized i n Table 1-3. H i g h and positive o~ values correlate to strong electron-withdrawing ability o f substituents.  Table 1-3. a values for different substituents.a Substituent  -CF  0.54  0.43  -CH  3  -0.17  -0.07  -H  0.00  0.00  -F -CI -Br  0.06 0.23 0.23  0.34 0.37  0.66  0.56  0.78  0.71  3  -CN -NQ a  2  0.39  Values are from ref. 120,121. A s a typical reaction to  determine  this  quantity,  ionization constants  of  the  carboxylic group i n substituted benzoic acids i n water at 25 °C has been s e l e c t e d ^ ; rj = l o g ( K / i Q , where K is the ionization constant  o f benzoic acid and  is that o f  substituted benzoic acid, m and p denote that the O" value was determined at meta and para substitution respectively.  A s s h o w n i n Table 1-3, the - C F group does not have the highest a values and thus it is 3  not the strongest electton-wididrawing group. fluorine  (3.98 o n Pauling's scale)122  a  n  H o w e v e r , due to the high electronegativity o f  d relatively similar sizes o f the fluorine and hydrogen  32  atoms (the van der Waal's radii of F and H are 1.35 and 1.20 A, respectively) 123 fluorinated molecules have some unique properties. 124 substituents  increase  the  oxidative,  The above-mentioned characteristics of fluorine  hydrolytic,  and  thermal  stability  of  fluorinated  molecules compared to the parent hydrocarbon (the C - F bond energy is about 116 kcal/mol.124 cf. the C - H bond energy of 104 kcal/mol.125). I the trifluoromethyl group is at least 2.2 A126.  n  addition, the estimated van der Waals radius of  Despite the similar sizes of - F and - H , the  trifluoromethyl group is slightly larger than the methyl group (2.0  A 1 2 3 ) . Thus, the thermal  stability and steric bulkiness of the trifluoromethyl group should be advantageous  of the  protection of the macrocycle.  In summary, the unique electronic, steric, and physical properties of the —CF group may 3  be able to make P-trifluoromethyl-^j-o-tettaphenylporphyrin metal complexes ideal candidates as potential P-450 mimics.  C. S y n t h e t c i s t r a t e g y for P t r i f l u o r o m e t h y l a t i o n of w e s o t e t r a p h e n y p lo r p h y r n i Although 3,4-bis(trifluoromethyl)pyrrole  is available  in excellent yieldsl27,128  ;  n  o  condensation of this pyrrole with aldehydes to give a P-octalds(tofluorometliyl)-porphyrin has yet been reported. Presumably, cyclization with aldehydes is unlikely due to the low electron density at the a positions of the pyrrole. 129 Therefore, direct P-trifluoromeurylation of a porphyrin is the preferred route to p-ttifluorometiiylporphyrins.  /. Brief overview of trifluoromethylation The synthesis of perfluoroalkyl-substituted aromatics falls into three classes.  33  a. Fluorination of an existing aryl substituent (Scheme 1-3) As examples of this category, (a) substitution of chloride substituents of a trichloromethyl group with antimony trifluoride or hydrogen fluoride^O and (b) fluorination of a carboxylic acid by sulfur tetrafluoride with hydrogen fluoride as a catalyst^ ! have been reported. Obviously, the 3  drawbacks of the use of these methods include challenges in the preparation of appropriately substituted ^j-o-tetraphenylporphyrins and technical difficulties associated with the handling of SbF , H F and SF .132 Therefore, the application of these methods is limited. 3  4  00  rr  °' » fY° *  Ch3  C  0  0  2  a  SF  H  SbF orH 3  4  F > >  ^ r -  C  F  3  H F (cat.)  (b)  S c h e m e 1-3. Fluorination of an existing aryl substituent. (a) Substitution of chloride substituents with fluoride, and (b) fluorination of a carboxylic acid.  b. Introduction of trifluoromethyl groups (1) Transfer of CF f (Scheme l-4(a)) Perfluoroalkyl organometallic reagents have been studied extensively and it is known that a number of them, especially those of copper, mercury, cadmium, and zinc, are useful reagents for trifluoromethyl anion transfer to organic compounds. 1 compounds  3 3  Some organosilicon perfluoroalkyl  are also good trifluoromethyl anion transfer reagents, although only a few  applications to aromatic compounds have been reported. ^ ^ 3  34  X  CF,  (a) CF3M  e.g.  or  (CF ) M M=Cu, Hg, Cd, or Zn  X=Ior Br  3  2  (b)  02N  O^Ci  ^  N02  F C 3  22  ,  dryTHF  "4 S c h e m e 1-4. Introduction o f a trifluoromethyl group.(a) Transfer o f CF ~, and (b) transfer o f C F . 3  +  3  (2) Transfer of CF  + }  (Scheme 1-4(b))  Electrophilic perfluoroalkylating reagents are  also k n o w n .  Indeed, T a m i a k i ^ / a / .  synthesized (3- and ^j o-tafluoromethyl-5,15-bis(3,5-di-Abutylphenyl)porphyrins (21) -  (tofluoromethyl)-3,7-dinitrobenzothiophene  trifluoromethanesulfonate  (22)  i n dry  using STHF.^8  H o w e v e r , the yields were p o o r w i t h a mixture o f regioisomers obtained (16% o f 23, 4 % o f  24,  and 1 % o f 25 for M = Z n ( I I ) ) and 55 - 62 % o f starting materials were tecovered. U n l i k e phalogenation34,44,70-77 o f p-pyrrolic positions.  n i t r a t i o n , this m e t h o d seems to be inefficient for the modification 37  o  r  35  O f the above-mentioned methods and reagents, perfluoroalkylcopper reagents have received more attention than any other perfluoroalkyl organometallic compounds due to their ease of preparation and ready availability. 133 A number of examples of perfluoroalkylation of aromatic compounds have been reported. 133  However, there are no literature reports of the  application of perfluoroalkylcopper reagents to porphyrins.  2. Copper assisted trifluoromethylation The  pioneering work of McLoughlin and Throwerl32  a n c  J  Kobayashi ^i?/. 136,137  identified trifluoromethyl copper reagents as ideal coupling reagents for trifluoromethylation of aromatic halides. Perfluoroalkylcopper reagents have been prepared by the following three methods: (i) reaction of C F I or C F B r with metallic copper in a coordinating solvent at elevated 3  2  2  temperatures 132; (ii) pyrolysis of tafluoroacetate in the presence of Cu(T) halides!36,137. (iii) metathesis reactions of mfluoromethylorganometallic reagents with metallic copper or Cu(T) halides. In method (i), there is a technical difficulty in handling the precursors (in spite of the high temperature (100-140°C) of the reactions, the b.p. of perfluoromethyl halide is low, e.g. CF I: —22.5°C) and another major drawback is the high cost of the perfluoroalkylhalide.133 3  Methods (ii) and (iii) do not require special equipment and the cost of the materials are reasonable. 133 Methods (ii) and (iii) are detailed below.  a. CF Cu from pyrolysis of sodium trifluoromethyl acetate in the presence of Cu(I) halide 3  Trifluoromethylation via pyrolysis of sodium or potassium trifluoromethylacetate in the presence of Cu(I) halide is the least costly and least hazardous methodology for introduction of the trifluoromethyl group into aromatic compounds.133 the  presence  of  Cu(I) halide,  pyrolysis,  or  As shown in scheme 1-5 (Path A), in  decomposition (decarboxylation)  of  sodium  36  NMP Arl + C F C 0 N a / C u l 3  •  2  1  4  ° -  1  6  0  °  ArCF  (Path A)  3  40-78o/  C  CF H  -^U-  3  0  + ArH  (Path B)  (side products) Scheme 1-5. Trifluoromethylation of aromatic halide by pyrolysis of C F C 0 N a . 3  2  trifluoroacetate in aprotic polar solvents such as N-methylpyrrolidone (NMP) or D M F at around 150 °C generates the active trifluoromethylating agent C F C u and copper assisted substitution 3  gives the trifluoromethyl aromatic compound. Residual water, which largely arises from the hygroscopic trifluoroacetate salt, causes serious problems including loss of active C F C u and 3  dehalogenation of the substrate to form fluoroform and hydrogenated aromatic compounds as shown in Path B. In order to minimize the side reaction, Freskos^8 employed a tolueneazeotrope to distill off any trace water before the reaction temperature was brought up to 155 °C (Figure 1-13). With this method, only two equivalents  of perfluorocarboxylate are  required and the yields of the products were moderate to excellent.  CF CF  toluene + water  2  distillation at 120°C  155 °C 2h  toluene DMF CF CF C0 K Cu? trace water 3  F i g u r e 1-13.  2  3  90 %  2  Removal of  water  by  use  pentafluoroethylation of a-iodonaphthalene.  of  a  toluene-azeotrope  in  the  37  b. CF Cu from metathesis of trifluoromethylcadmium with Cu(I) halide }  (1) Trifluoromethylation B u r t o n et al. showed that difluoromemylcadmiurn, C F - C d (a mixture o f C F C d X and 3  3  ( C F ) C d , X = C 1 or Br) is an excellent precursor for generation o f the active C F " transfer agent, 3  2  3  CF Cu, 3  and  can  b e used  for high-yield  multiple  trifluoromethylation  o f aromatic  halides. 133,139,140 -phg tnfluoromemylcadmium reagent undergoes metathesis, or an exchange reaction w i t h Cu(I) halide to give C F C u at - 40°C i n 90 - 100 % yield ( 1 . 2 ) .  1 4 0  3  (CF)Cd  C u X  U h U d B r  -40°C  32  3  ^  C  F  3  C  In-situ generated  u  C F C u then attacks the brominated or iodinated site o f aromatic compounds. 133,139 3  s  ^  e  reaction is perfluoroalkyl chain oligomerization w h i c h occurs at higher temperature (equations (1.3)  a n d (1.4)).133  However,  addition  of  the  same  volume  of  hexamethylphosphoramide ( H M P A ) to the volume o f trifluoromethylcadmium reagent, w h i c h is given at 1 M i n D M F solution,139 inhibits the oligomerization.133  CF Cu 3  CF Cu 3  y  »» CCFCu F 3  (1.3)  2  D M F  • CF(CF)Cu 90-100°C 3  2n  (1.4)  (2) Synthesis of trifluoromethylcadmium Trifluorometiiylcadmium is synthesized from dibromodifluoromethane and c a d m i u m powder i n D M F . T h e proposed reaction mechanisms!39 r e s h o w n i n equation (1.5) - (1.11). a  T h e reaction is initiated by electron transfer from c a d m i u m to the electronegative carbon i n C F B r (1.5). T h i s is followed by a second electron transfer to facilitate the loss o f bromide 2  2  ions (1.6) and to give a reactive difluorocarbene (26) (1.7). T h i s species reacts w i t h D M F (1.8)  38  and the resultant dimemyl(iifluoromemylamine (27) releases fluoride ion (1.9) which reacts with another molecule of difluorocarbene to form a trifluoromethyl anion (1.10). Finally the C F ~ ion 3  combines with CdJ3r or C d +  to form C F C d B r and(CF ) Cd, respectively (1.11).  2 +  3  CF Br 2  2  3  + Cd  Cd [CF Br ]* 2  -  Cd  [CF Br]"  •  : C F + Br"  2  2  2  2  Cd [CF Br f 2  + (CH ) NCH=0 3  2  2 +  + [ C F B r ] " + Br" 2  3  2  2  ^ [ ( C H ) N = C F H ] + F" +  2  3  (1.6)  (1.7)  2  *~ ( C H ) N C F H + C O 27  2  (CH ) NCF H 3  (1.5)  +  +  :CF 26  2  2  (1.8)  (1.9)  27 :CF  2  + F"  -  CF "  (1.10)  3  26 CF " 3  Br and C d  2  ^  ( C  p ) 3  2 C d  +  C  F CdBr 3  (l.il)  Thus, Cu(I) assisted trifluoromethylation is an efficient method for the preparation of trifluoromethylated aromatic compounds.  D. A n a l y s i s of p o r p h y r n is /. UV-visible absorption spectroscopy a. Characteristics of UV-visible absorption spectra ofporphyrins and metalloporphyrins Porphyrins exhibit characteristic absorption properties in the UV-visible region. 141,142 j  n  Figure 1-14, UV-visible absorption spectra of free-base, diprotonated, and metallated (with  F i g u r e 1-14. U V - v i s i b l e spectra o f /^.ro-tettaphenylporphyrins i n C H C 1 . 2  (a) H T P P (2a) 2  (solid line) and H T P P  Q bands are multiplied b y five.  4  2 +  (narrow line), (b) Z n T P P (2b).  2  "  40  Zn(II)) forms o f ^.ro-teteaphenylporphyrin (TPP) are shown. Porphyrins show an intense absorption near 400 n m (s ~ 4 x 1 0 M ' c m ) , w h i c h is referred to as the Soret band (also called 5  the B band).  1  Porphyrins also exhibit less intense bands, usually found between 500 and  700 n m , w h i c h are referred to as the Q bands.141,142 - p h origins o f the Soret and the Q bands e  are 71-71* excitation from the ground state to the second and the first excited singlet state, respectively. 142 T h e Q bands split into two bands!42  for  porphyrins such as Z n ( T P P ) (2b)  (Figure 1-8) as shown i n Figure l-14(b). T h e lower-energy band o f the t w o Q bands, w h i c h is referred to as Q (0,0), corresponds to the excitation o f an electron from the ground to the lowest-energy excited singlet state and the higher-energy band, Q (1,0), including one mode o f vibrational excitation. 142 F o r the free-base, each Q band is further split into two bands due to the breaking o f the D  4i  symmetry o f the porphyrin ring by the central p r o t o n axis as D  2/l  symmetry is achieved (Figure 1-15).142 T h u s , Q (0,0) and Q (1,0) split into 0,(0,0), Q (0,0) and y  Q (1,0), Q (1,0).142 X  nitrogen  and  the  T h e addition o f acid to the free-base results i n protonation o f each inner spectrum  of  porphyrin  dication (Figure 1-15)  returns  to  D - t y p e (Figure 1-14(a) (gray line). 142 4h  2+  H TPP  [H TPP]  2  2+  4  D  4h  Figure 1-15. Symmetries o f Z n ( T P P ) (2b), H T P P (2a) a n d [ H T P P ] 2  4  2  the  41  b. Electron-withdrawing effects on UV-visible absorption spectra Electron-withclrawing substituents ( H O M O ) (ft)  and  the  lowest  stabilize the  unoccupied  highest  molecular  occupied molecular orbital  orbital  (LUMO)(7t*)  porphyrins.143 Since UV-visible spectra of porphyrins reflect the  orbitals  of  electronic transition,  7t-7t*  changes in the UV-visible absorption spectra are observed if the H O M O and the L U M O are j  affected (differently by the electronic effects of substituents.39,144  n  o  n  e  c a s e ;  such as in the  example shown in Figure 1-16, (only Q bands are shown - the Soret band also shifts to a longer wavelength)!41 it is known that replacement of an ethyl group of etioporphyrin I (28) ;  with a  electton-withdrawing carboxylic group results in a red-shift of the UV-visible bands in rhodoporphyrin X V (29). HOMO-LUMO  The red-shifts of the absorption bands imply contraction of the  gap. Alternatively, replacement  of  ^jo-phenyl groups  (Figure 1-8) with pentafluorophenyl groups to give H T P F P P (4a) 2  of  H TPP 2  (2a)  (Figure 1-8) causes the bands  to shift from 418 (Soret), 514, 549, 590, and 646 nm (Q bands) for 2a in C H C 1 to 410, 505, 2  2  535, 582, and 645 nm for 4a, i.e. a minor blue-shift. This phenomenon implies that the H O M O L U M O gap is expanded by the electton-withdrawing effect of the wwo-perfluorophenyl groups. The blue-shifts of the absorption bands are also observed in P-perfluoro-wwo-arylporphyrins, 12a,  13a,  and 14a (Figure 1-8)  from  H TPP. 2  Accordingly, either  HOMO-LUMO  gap  contraction (red-shift) or expansion (blue-shift) may occur due to the introduction of electtonwithdrawing substituents. Unfortunately, it is rare to observe a pure electronic effect of substituents on the UV-visible spectra, for it is well known that macrocycle distortion causes redshifts in UV-visible absorption bands of the porphyrin.144-147 spectrum  of  severely  distorted  tettaphenylporphyrin (Zn(OMTPP)) (30)  Zn(II)  complex  p  o r  example, the UV-visible of  P-octamethyl-«?wo-  (p.43)(442, 574, and 630 nm in C H . C L )  1 4 7  shows  500  550  600  650  500  Wavelength (nm)  Porphyrin  3  (28)  Me  R h o d o p o r p h y r i n - X V (29)  Me  7  650  8  12  13  17  18  Et  Me Et  Me  Et  Me  Et  Et  Me Et  Me  C0 H  H  Me  5, 10, 15 and 20 = H , M e = m e t h y l , E t = e t h y l ,  F i g u r e 1-16.  600  Wavelength (nm)  2  Etioporphyrin-I  550  P  H  P  2  = CH CH C0 H 2  2  2  E x a m p l e o f the U V - v i s i b l e spectral change by electton-withdrawing  effects. U V - v i s i b l e spectra were adapted f r o m reference 141.  43  enormous red-shifts compared to Z n ( T P P ) (419, 548, and 582 n m i n C H j C L ) . Macrocycle distortion causes destabilization o f the H O M O w h i c h also leads to contraction o f the H O M O L U M O gap, and thus the red-shifts o f the absorption b a n d s .  1 4 4  "  1 4 6  Z n ( O M T P P ) (30)  2. Redox potentials ofporphyrins a. General redox properties of porphyrins in non-aqueous media (1) Technique, solvent, and supporting electrolytes A l t h o u g h redox properties o f porphyrins have been studied by various techniques  1 4 8  ,  cyclic voltammetry has been the m e t h o d o f choice for the investigation o f the electrochemisty o f porphyrins,  1 4 8  '  and several solvents such as D M F , D M S O , M e C N , B u C N , P h C N , or  1 4 9  C H C 1 have been used. 9 , i 5 0 Q 1 4  2  2  n  e  Q  f fa most c o m m o n solvents is C H C 1 due to its weak e  2  2  binding properties, ability to solubilize porphyrins and its large cathodic and anodic range close to ± 1.9 V vs. S C E . 5 0 Therefore, a wide range o f redox potentials can be studied i n C H C 1 . 5 0 1  1  2  2  T h e most c o m m o n supporting electrolytes, w h i c h are used to increase the conductivity o f the solution, (TEAP),  are  tetrabutylammonium  tetrabutylammonium  perchlorate  (TBAP),  tetrafluoroborate  tettaethylammonium  (TBABF ), 4  and  perchlorate  tetrabutylammonium  hexafluorophosphate ( T B A P F J i n w h i c h C 1 0 , B F " , and P F " can be considered as n o n - b i n d i n g 4  4  6  anions. A l l o f the salts are highly soluble i n non-aqueous solvents.  44  (2) Porphyrinringredox properties in free-base and metalloporphyrins Ftee-base and many metalloporphyrins undergo two one-electron oxidations and two oneelectron reductions, all of which occur at the conjugated 7t-ring system of the porphyrin macrocycle. 1^0  Figure 1-17 shows the cyclic voltammogram of H T P P (2a) 2  in CH C1 , which 2  2  reveals a typical example of two one-electron oxidations and two one-electron reductions. The former reactions correspond to the movement of two electrons from the H O M O and to the L U M O . Therefore, the difference in the half-wave potentials for the first oxidation and the first reduction, E ° ( l ) - E, / (1), is considered to correspond to the size of the H O M O - L U M O r  /2  gap.  1 4 9  -  2  A systematic study showed that E™ (1) - E $ ( l ) = 2.25 ± 0.15 V and constant  1 5 0  2  differences between E,%(1) and E° (2)) (=AE ° ) and between E $ ( l ) and E$(2) (=AE / ) were X  /2  1  /  re  2  1  2  observed for 25 metal complexes of octaethylporphyrin (OEP).151 The H O M O - L U M O gap, E ° ( l ) - E{/ (1) = 2.25 V approximately agrees with the theoretically calculated value of 2.18 eV /2  2  for most metalloporphyrins.152 A similar experimental observation was also obtained for the different metal complexes of TPP.153 Thus, ring redox potentials of a porphyrin are pretty much constant throughout the free-base and the series of metal complexes.  (3) Iron porphyrins As this thesis describes some electrochemistry of iron porphyrins, redox properties of iron porphyrins are briefly described here.  Most synthetic iron porphyrins show three to four electron transfer reactions in a variety of nonaqueous solvents. 150  Figure 1-18 shows a cyclic voltammogram of Fe(TPP)Cl  (Figure 1-8) measured by the author. A reduction Fe(III) to  (2d)  Fe(ir) generally occurs between +0.2  and —0.5 V vs. SCE.150 The most negative reduction potential shown could be Fe(II)/Fe(T) or  Ph 2a  E E l  ] / 2  (2):  7 (l): 2  Ev (l): 2  p  +  e <—  p-+  +  e" <-  P  + e"  P'-  +  l  2 +  <—  —> p-+  P  -> P'-  e" <- ->  p2-  i  i  i  M  E°; (2) 2  r  rf  i  1 - r - i ^ /r\\ re  1E  1 H O M O - L U M O gap  •1.50  1 / 2  (2)  j  , j  1 E^O)  i  Er; (i) 2  i  M . 0 0 »0.50  i 0.00  i  i  •  -0.50 -1.00 -1.50  V vs. S C E Figure 1-17. Cyclic v o l t a m m o g r a m o f H T P P (2a) i n C H C 1 , 0.1 M T B A P ; 2  scan rate, 50 m V / s . A d a p t e d f r o m reference 149.  2  2  F i g u r e 1-18.  Cyclic voltammogram o f F e ( T P P ) C l  scan rate, 100 m V / s ; F c / F c  +  (2d) i n C H C 1 , 0.1 M T B A P F 2  2  = ferrocene/ferrocenium coupling, 0.46 V vs. S C E .  6  47  Fe(II)/(Fe(II) porphyrin 7t-anion) couple.150 subject of controversy. 154,155  -ph assignment of this potential has long been a e  Some studies show the likeliness of the assignment of Fe(I)  depending on the solution conditions and porphyrins.150 Each anodic reaction around ~1.1 V and ~1.6 V corresponds to removal of an electron from the T P P macrocycle. 150  b. Effects of substituents on the redox potentials of derivatives of TPP (1) Aryl-ring-substituted TPPs Kadish and Morrison measured half-wave potentials of seven H TP(/)-X)P (31a) ((/>-X) 2  represents the para positions of meso-phenyl groups are substituted by substituent X) in various solvents. 156 In order to analyze the results quantitatively as a function ofthe substituent, Kadish and Morrison employed the Hammett linear free energy equation and expressed a relationship as shown in equation (1.12), where E *  AE  1 / 2  = E*  2  2  and E , "  2  are the half-wave potentials for T P P substituted  - E ^ = erp  (1.12)  with X and H at the phenyl para-position, respectively, andCTis a Hammett constant for X , and p is a constant value under the same experimental conditions. As shown in Figure 1-19, plots of E  1 / 2  values vs. 4CT for each electrode reaction were linear, indicating that macrocycle oxidations  become more difficult and reductions become easier as the substituents become more electronwithdrawing. 156  Similarly, five electrode reactions (P-Fe(T)/P~"-Fe(I), where P is porphyrin, in addition to the  four  electrode  reactions  in  Figure 1-18)  were  examined  for  nineteen  FefTPf>X)P)Cl (31b) and Fe(TP(w-X)P)Cl (32b) systems. Linearity of the E reactions in C H C 1 2  2  was observed. 157  1 / 2  different  vs. 4CT for these  Linearity of the plots was also observed for other  49  metaUoporphyrin species such as those containing C o ^ I ) ^ Mn(III) 59,160 Cu(II) 0, and 1  1  16  >  Zn(II). 0 16  (2) B-Substituted TPPs The electrochemistry of P-substituted TPPs has been analyzed in two ways. The first method of analysis involves a series of p-mono-substituted TPPs with different substituents. The second analysis involves the series of TPPs P-substituted with zero to eight substituents of the same kind.  (a) P - M o n o - s u b s t i t u t e d T P P s with different substituents  Giraudeau et al. examined the ring redox potentials of T P P substituted at a p-pyrrolic posistion by substituent X (H TPP(X)) (33) in C H C 1 . 2  TPPs, (Figure 1-19), E  1 / 2  2  2  1 6 1  As observed in the phenyl substituted  vs. 4a plots showed that the oxidation and the reduction potentials  increase almost linearly with the increase of a value of the substituents.  33 X = H , O E t , Br, CI, C N , N Q  2  161  50  (b) P - S u b s t i t u t e d T P P s w i t h m o r e t h a n o n e s u b s t i t u e n t o f t h e s a m e  kind  Giraudeau et al. studied a series o f P-cyano-wtf.ro-tettaphenylporphyrins (34). Figure 1-20 shows plots o f the first oxidation and reduction vs. the number o f substituents for the freebase (34a) and the C u complex (34c).161 Analysis o f the plots i n Figure 1-20 (p.51) reveals that the reduction potentials change linearly w i t h the number o f cyano groups but that plots o f the oxidation potentials are non-linear for b o t h free-base and C u complexes.  Extreme cases o f the non-linearity o f the E  1 / 2  for the oxidation vs. number o f substituents  are shown by K a d i s h eta/., w h o measured the redox potentials o f a series o f P-brominated T P P derivatives (35). 162-164  Figure 1-21 (p.52) shows the plots o f E  1 / 2  for the first oxidation and  reduction vs. extent o f brornination for 35a. 162 F o r the first reduction, (Fe(in)/Fe(II)) linearity is maintained, but this is n o t the case for the oxidation; the first oxidation potential is m a x i m i z e d at x = 2 for 35a as shown i n Figure 1-21.162 Similar results were obtained for Zn(II) complexes, 35b.l64  Ochsenbein et al. demonstrated, by using cyclic voltammetry and X - r a y crystal structure studies,  that  conformational changes  within  molecules  affect  the redox  potentials o f  P-halogenated tetraarylporphyrins (36 - 39).165 Crystal structures o f 3a and 36 - 38 (/mo-mesityl groups omitted i n the diagrams o f the X - r a y crystal structures) show that the macrocycle is progressively distorted as the size and number o f the substituents increases. This is presumably due to increased steric interactions between the substituents (Figure 1-22 (p.53)). (p.54) shows the first reduction and oxidation E o f the substituents, the increase o f the E f  c 2  1 / 2  Table 1-4  for 3a and 36 - 38. Regardless o f the nature  ( A E ^ ) w i t h increasing number o f the substituents is 2  -1.5" 0  1  2  3  # of C N group Figure 1-20. First reduction(O) and oxidation potentials (•) vs. # of C N groups for (a) H T P P ( C N ) (34a) and (b) C u T P P ( C N ) (34c). The plots were produced 2  X  from the values reported in reference 161.  x  Figure 1-22. Side view of the crystal structures of H T M P (3a), H T M P C 1 (36) 2  2  4  H T M P B r (37), and H T M P C 1 (38) (the meso-mesityl groups are omitted for 2  4  2  8  clarity). Adapted from reference 165.  54  almost constant (— +0.3 V), while A E  1 / 2  is obviously lower in the severely distorted porphyrins  than in the planar macrocycles. This infers that the H O M O is destabilized by macrocycle distortion. The results shown in this section correlate to the red-shifts ( H O M O - L U M O gap contraction) observed in the UV-visible spectra which also correspond with macrocycle distortion (see section D.l.b.).  T a b l e 1-4. The first reduction and oxidation potentials for 36 Porphyrin  Halogen substituents  3a 36  pRed  T7Rcd  —  -1.41  +0.91  4C1  -1.12  ^1/2  ^1/2 +0.29  8C1  3a 4Br  -0.10  -0.85  +1.05  -1.41  +0.91  -1.09  +0.21 +1.12  +0.25  39  8Br  AE*1 +0.24  +0.32  37  a  +1.15 +0.27  38  39.  -0.84  -0.13 +0.99  E in V vs. SCE: solvent CH C1 , electrolyte T B A P F . T=25 °C, ref.165 a  1 / 2  2  2  6  (3) Conclusion In summary, for porphyrin macrocycles without conformational change, the presence of election-withdrawing effects linearly increases both the first reduction and the first oxidation potentials. This is the case for phenyl-substituted and P-mono-substituted TPPs. However, when the macrocycle is distorted, an expected increase in the first oxidation potential by an electronwithdrawing effect is offset by destabilization of the H O M O due to macrocycle distortion, while linearity for the first reduction potential (ring reduction or Fe(III)/Fe(II)) vs. an expected electron-withdrawing effect is maintained. Therefore, one can deduce the electron-withdrawing  55  effects imposed upon a porphyrin macrocycle by comparing the first reduction potential of one porphyrin with the value of another.  3. H NMR  spectroscopy  a. Porphyrin  ring current effect  1  ' H N M R spectroscopy of porphyrins is a valuable technique to enable analysis and characterization. Chemical shifts observed in ' H N M R spectra of diamagnetic porphyrins can be assigned and rationalized by considering the porphyrin ring current effect which is characteristic of aromatic c o m p o u n d s . ! ' ! 66  67  p  o r  a  n  aromatic system such as a porphyrin, the magnetic  deshielding resulting from the ring current is positive for nuclei on the outside of the ring current (for  meso and  proton).  i 6 6  jl  P-substituents), and negative for nuclei positioned within the ring current (for N - H 6 7  This shielding and deshielding results in massive chemical shifts of signals  compared to those of signals due to non-aromatic systems. Figure 1-23 (p.56) shows the ' H N M R spectrum of H T P P (2a) 2  in CDC1  3  at 298 K recorded by the author. A remarkable  deshielding effect due to the induced paramagnetic field that is caused by the ring current is observed as a downfield shift of the signal due to the p-pyrrolic proton (8.86 ppm) of the porphyrin compared to that of pyrrole (~6 p p m ) .  1 6 7  >  1 6 8  O n the contrary, the N - H proton is  strongly shielded by the induced diamagnetic field and the effect is observed as an enormous upfield  chemical  shift (-2.76 ppm)  of  N - H signal (7-12 ppm) in pyrrole i t s e l f .  the 1 6 7  '  porphyrin  N-H  compared  to  that  of  1 6 8  b. Concentration effect  It is well known that porphyrins aggregate in s o l u t i o n  1 6 6  '  1 6 9  and this phenomenon has  been extensively studied in solution using N M R spectroscopy. 0-172 j± typical experiment to 17  a  2a a: P-pyrrole H (8.86 ppm)  b: ortbo-phenyl H (8.22 ppm) c: meta,para-phenyl H (7.76 ppm) d: N - H (-2.76 ppm)  I '  1  10  1  1  I ' '  9  1  ' I  1  ' '  8  1  I  1  ' ' ' I ' '  7  1  6  1  I  1  1  5  I  1  1  1  1  4  I ' ' '-r-p-"-i-p-'-'-H  3  2  1  ' ' ' ' I ' ' '  0  1  I  1  ' ' '-T'-i-r-r  -1 -2 -3  Chemical shift (ppm)  F i g u r e 1-23.  200 M H z H N M R spectrum of H T P P (2a) in C D C 1 at 298 K . X  2  3  57  detect  aggregation  of  porphyrins  is  to  measure  the  chemical  shift  at  various  concentrations. 71,172  Figure 1-24 (p.58) shows the change of the chemical shift due to  meso-ptoton of 40a  with the concentration change, according to Ono etal.^72 rj  1  ue  71-71 aggregation, the chemical shift of the shielded meso-ptoton is shifted by the induced diamagnetic field of the porphyrins. Furthermore, the same experiment with 40b less aggregation occurs compared to the electron-deficient 40a shown).  showed that  (the result for 40b  is not  The reason why the electron-deficient porphyrin tends to aggregate more is not well  understood.  c. N-H tautomerism Figure 1-25 (p.59) shows the N - H tautomerism for ^jo-tetraphenylporphyrin. Several other tautomers are also possible by locating two inner protons on adjacent nitrogens!  66  (the  structures are not shown) but they are less stable due to penetration of each hydrogen into the van der Waals sphere of the other.! ! Although two tautomers (41a 4  and 41b)  exist as the most  probable structures! ! for H T P P , H and H cannot be distinguished using N M R spectroscopy 4  A  B  2  due to the fast exchange between 41a and 41b In other words, H T P P of symmetry D 2  2 h  on the N M R time scale at room temperature.!  is observed as an average of 41a  and 41b  of D  66  4 h  symmetry at room temperature by N M R spectroscopy. However, this exchange is slowed below 220 K and two signals for H and H can be observed.! ,174 As shown in Figure 1-25, H is A  B  73  A  located on the conjugated 187t-electron pathway (presented by the dotted line) and H is located B  on the isolated double bonds.  Crossley et al. studied tautomerism of sixteen different (3-mono-substimted-TPPs (42)  by  *H N M R spectroscopy at 200 K in C D C 1 and found that the position of the N H tautomeric 2  2  t  o  F i g u r e 1-24. for 40a.  Plot of  chemical shift of meso-H vs. porphyrin concentration  Adapted from reference  172.  59  F i g u r e 1-25.  (2a).  Tautomerism in H T P P 2  Ellipses indicate isolated  double bonds.  equilibrium is affected by the nature of the s u b s t i t u e n t s . A s shown in Figure 1-26 (p.60), for R = C N , N 0 , O C O P h , C l , Br, C H O , O M e , SPh, N H C O M e , and O H G g Y electronar  el  2  withdrawing groups) the dominant tautomer has the substituent positioned on an isolated double bond. For R = C H = C H , N H , ( C H ^ M e , Me, and C H M e , the major tautomer has the 2  2  2  substituent positioned on the aromatic derealization pathway. Thus, the effects of electronwithdrawing substituents may be appreciated by analysis of the ' H N M R spectra of porphyrins at low temperature, and assessment of N H tautomerism observed therein.  4. Spectrophotometric titration In this section, two techniques for the evaluation of electron-deficiency of a porphyrin by spectrophotometry are described.  a. Evaluation ofpK o/NH a  PH  2+ 2 4  P 4  +  K  •  PH, •  P3 K  PK  2  PH • ?  PKI  PH" —  -  o  P " 2  ( 1 . 1 3 )  The free-base parent porphyrin (PEQ can be protonated twice on its imine type nitrogen atoms to form mono- (PH ) or di-cation (PH +  3  2+ 4  ) species, or can lose two pyrrole type protons  Ph  Ph  42a  42b  42a  R  >99 97 94 94 91 84 82  CN N0 OCOPh  81 73 61 38 33 22 21 19 9  42b -  2  CI Br CHO OMe SPh NHCOMe OH CH OH 2  CH=CH NH (CH^Me 2  2  Me CHMe  2  3 6 6 9 16 18 19 27 39 62 67 78 79 81 91  F i g u r e 1-26. Relative populations of 42a and 42b at 200 K in CD C1 . 2  Adapted from reference 175.  2  61  to produce mono- (PH') or di-anion (P ~), equation (1.13).  169  well documented to be between 3 and 9.141,169 Q  t r a r y , piC, and pK are estimated to  2  be in the order of 1 6 ^  76  n m  e  con  The values p X and pi<C have been 3  4  2  and have not been studied well.  Recently, Woller and DiMagno have determined the piC, values of P-octafluoro-w&roH T P P F (12a)  tetraarylporphyrins  2  H T P F P P F (14a)  and  8  2  8  (Figure 1-8,  p. 11)  by  spectrophotometric titration with D B U in CH C1 .36 The titration showed a difference of +3.9 2  and + 0.2  xpK  2  units from D B U for 12a and 14a, respectively. Since this method of analysis is  a  performed in a common solvent for porphyrins (CH^Cy, it should be applicable to other electron-deficient porphyrins in order to assess the extent of electron density withdrawal from the macrocycle by the substituents.  b. Determination of central metal — ligand binding constant  PCo(ll) + B  -  PCo(ll)B  (1.14)  K  2  PCo(ll)B + B  •  PCo(ll)B  (1.15)  2  P = porphyrin, B = Lewis base It is known that Lewis bases such as pyridine bind to four-coordinate porphyrin cobalt complexes  as shown in equations (1.14) and (1.15). 177-180  coordination of Co(TP(p-OCH )P) (43) 3  influence on the 0 Smirnov ^(2/180  Walker studied the axial  (p.62) with amines to investigate the electronic and steric  binding behavior of the Co(II) porphyrin complex.178  2  evaluated  P-cyanoporphyrin (34c)  and  the  electron-deficiency  Co(II) complexes  of  of  the  Co(II)  Lrn et alX^^ and complex  P-octafluoroporphyrins (12h  and  of 14h),  62  Ar' 43  respectively. As summarized in Table 1-5, electron-deficient porphyrins show higher log lvalues than that of 43, that is, 34c,  Thus,  12h,  and 14h bind pyridine more tighdy than 43.  central metal-axial  ligand binding constants  may  also  be  determined  by  spectrophotometric titration and the electron-deficiency of porphyrins can be evaluated by comparing the binding constants.  T a b l e 1-5. Formation constants for pyridine binding in C H C 1 at 25°C 2  Porphyrin  43 34c 12h 14h  2  log*; 2.7  logK  4.2 4.3 5.9  -0.35 -0.08  179 180  1.03  180  2  Reference 178  63 Electron-deficiency alone may not guarantee high efficiency and robustness of porphyrin catalysts but now we are sure that electron-deficiency is a necessity for the desired oxidation catalyst.  Thus,  development  evaluation of  P-450  of the mimics.  electron-deficiency As  shown  above,  of porphyrins is important in UV-visible,  1  H NMR  the  spectroscopy,  electrochemistry, X-ray crystallography, and spectrophotometic titration can all be used, alone and in combination, to assess the effects of electron-withdrawing substituents on the properties of porphyrins and metalloporphyrins.  E. G o a s l of t h i st h e s i s The overall goal of this thesis is to contribute to the research field of cyctochrome P-450 rnirnics. The initial approach in search of an active and robust metalloporphyrin as a P-450 mimic was to prepare novel electron-deficient  (3-trifluoromethyl-^j'o-tetraphenylporphyrins  including Zn(II), Co(II), and Fe(III) complexes of the species. The major part of this thesis concentrates on analysis of the electron-deficiency of the porphyrins by the UV-visible and N M R spectroscopies,  cyclic voltammetry, and X-ray crystallography. In order to make the  properties of the novel porphyrins clearer, the results of analysis are compared with known electron-deficient porphyrins. Electron-releasing P-methyl-wtfJo-tetraphenylporphyrins were also prepared to show an interesting comparison with P-trifluoromethylporphyrin in electronic and structural effects of the substituents. Finally results of oxidation of cyclohexane and cyclohexene using Fe(III) porphyrins as catalysts are shown, and the usefulness of P-trifluoromethyl-OTwotetraphenylporphyrins as P-450 mimics is discussed.  64  C H A P T E R II R e s u l t s and D i s c u s s i o n A. S y n t h e s s i of P t r i f l u o r o m e t h y l - and p m e t h y l m e s o t e t r a p h e n y p lo r p h y r n is The trifluoromethyl group may be an advantageous substituent when directly introduced onto the porphyrin macrocycle in order to improve the efficacy of metalloporphyrins as catalysts for oxidations due to its strong electron-withdrawing effect, bulkiness and stability (Chapter I, section B.3). Direct attachment of trifluoromethyl or perfluoroalkyl groups onto the porphyrin macrocycle  at  the  /w.ro-positions  porphin (I) (nomenclature,  of  P-positions of ^jo-diarylporphyrinl  18  p.viii) ,39,112 38  a n (  j  has been reported, but there are no reports  m  e  of  P-trifluoromethyl-w^o-tetraarylporphyrin in the literature. As described in chapter I, major players  in  the  development  of  P-450  mimics  using  synthetic  porphyrins  are  meso tettaarylporphyrins with electron-withdrawing substituents on the p-pyrrolic positions (see chapter I, section B.2.). Accordingly, the main purpose of this research is to initiate and investigate the chemistry of p-trifluoromethyl-^j"o-tetraphenylporphyrins. The first part of this section describes the synthesis of P-tjifluoromethyl-^j'o-porphyrins. The second part describes the synthesis of p-methyl-^jo-tetraphenylporphyrins. P-Methyl-wwo-tetraphenylporphyrins were compared with the corresponding P-trifluoromethyl- analogues in order to investigate the contrasting electronic characteristics of — C H and - C F 3  3  groups; electron-releasing vs. electron-  withdrawing(Table 1-3, p.31). Analysis by comparison may allow the effects of the electronwithdrawing C F group on the porphyrin macrocycle to be fully assessed. Finally, the synthesis of 3  Zn(II), Co(II), and Fe(III) complexes of P-tetealds(ttifluorometliyl)-OTW<?-tetJ:aphenylporphyrin is described. These metalloporphyrins were required to investigate the nature of the novel  65  porphyrins by cyclic voltammetry, spectrophotometric titration, and X-ray crystallography. The catalytic oxidation of cyclohexane and cyclohexene was subsequently conducted using novel Fe(III) porphyrins as catalysts.  /. Trifluoromethylation It has been mentioned that direct introduction of —CF groups onto the P-pyrrolic 3  postions of porphyrins is most easily achieved using Cu(I) assisted trifluoromethylation (chapter I, section C), which can be classified into two methods; (i) pyrolysis of trifluoromethyl acetate and (ii) metathesis of tofluoromethylcadniium in the presence of Cu(I) halide. The active trifluoromethylating reagent is C F C u and iodinated or brominated aromatic compounds are 3  required for both methods (Chapter I, section C.2.). Several proposed mechanisms for copper assisted nucleophilic substitution of halogenated aromatic compounds have been reviewed in the literature.  The  181  strategy  adopted  for  P-trifluoromethylation  is  shown  in  Scheme 2-1.  Metalloporphyrins as starting materials were required in order to prevent formation of the Cu(I) and Cu(II) complexes by the reaction of the free-base porphyrins with C F C u (even though a 3  free-base porphyrin was tested in a trifluoromethylation by the metathesis method). It has been reported that the use of iodinated aromatic compounds generally gives higher yields of trifluoromethyl aromatic compounds than the use of brominated ones for Cu(I) assisted trifluoromethylation.  133  Accordingly,  P-iodo-«?wo-tetraphenylporphyrins  would  be  ideal  substrates for Cu(I) assisted trifluoromethylation but the iodination of porphyrins has proved to be difficult, presumably due to the large steric bulk of the iodinium cation. ^ Although 18  iodination at the wwo-position of 5,15-diarylporphyrins is k n o w n ,  1 8 3  >!  8 4  effective multiple  66  P-iodination  has  not been  reported. 2 1 8  Consequendy,  the  precursors  chosen  were  P-brominated-OTtfj'o-tetraphenylporphyrins, which are much easier to prepare.  CF Cu by pyrolysis 3  Products  CF Cu by pyrolysis 3  Products  CF Cu by metathesis  Products  3  Br Ph M = 2H , Zn(ll), Cu(ll), Ni(ll) +  S c h e m e 2-1. Trifluoromethylation strategies.  The trifluoromethylation strategies outlined in Scheme 2-1 are described in detail in the following sections.  a. Synthesis ofprecursors The precursors chosen for Cu(I) assisted p-trifluoromethylation according to Scheme 2-1 were the readily obtainable CufTPPBr^fJc) (Scheme 2-2), H T P P B r ( 4 5 a ) , Zn(TPPBr ) ( 4 5 b ) , 2  Cu(TPPBr ) ( 4 5 c ) , and Ni(TPPBr ) (45d) 4  4  using N B S gave 7c^ 7  4  4  (Scheme 2-3). Bromination of 2c (Figure 1-8) and 2a  and 45a5,186 ^ yields of 75 - 80 %. The structures of the porphyrin 7c 1 8  and 45a were confirmed by mass spectrometry and  N M R spectroscopy. Zn(II), Cu(II), and  Ni(II) complexes of 45a were synthesized by the general porphyrin metallation m e t h o d .  68  This  67  metal insertion method is conducted in hot D M F in the presence of metal salts and produced the corresponding metalloporphyrins (45b,  45c,  and 45d)  b. Trifluoromethylation by pyrolysis of CFjCO^Na/  with > 90 % yield.  Cul  CufTPPBrg) (7c)  (1) Reaction using  Scheme 2-2 shows the attempted trifluoromethylation of Cu^TPPBrg) (7c)  by pyrolysis of  C F C 0 N a / C u l in D M F . Firstly, trace amount of water in the mixture was removed by the use 3  2  of a. toluene-azeotrope  under an atmosphere of N . After toluene was distilled out, the 2  temperature was then raised to 150- 155 °C, and held for 2 h under N . Pyrolysis of C F C 0 N a 2  3  2  was observed indirectly by gas evolution (presumed to be C O ^ for the first 10-15 min from the point the temperature had reached 150 °C.  The reaction was monitored by UV-visible  spectroscopy. The Soret band of the reaction mixture (466 nm for 7c) was observed at 434 nm at 30 min and no other changes were subsequently observed. Thin-layer chromatography (TLC) of the product mixture (44c)  using various combinations of organic solvents and silica-gel plates did  not show a satisfactory separation of the trifluoromethylated Cu(II) complexes resolution  EI  mass  tetraphenylporphyrinato Compounds 44c  spectrometry Cu(II) (44c  (x = 2), 44c  of  (x = 4))  (x = 3), 44c  44c as  showed the  major  (x = 5), and 44c  ( 4 4 c ) . Low  tettalds(trifluoromethyl)-^j-oproduct  in  100%  intensity.  (x = 6) were also detected in 30, 74,  57, and 2 % intensities respectively. N o sign of bromine groups on porphyrins in the reaction mixture was observed by mass spectrometry. Presumably reductive elimination of halogen had occurred. 187 A free-base mixture (44b) concentrated H S 0 2  mixture 44a  4  was obtained when Cu(II) complex 44c was treated with  and neutralized with 10 % aqueous N a H C 0 . 3  T L C analysis of free-base  showed a better resolution than that observed for the Cu(II) complex mixture  44c  and at least six compounds were observed by T L C analysis. Since the spots on the T L C plate  68  Ph 44a TLC  T More than 6 compounds  S c h e m e 2-2. Trifluoromethylation of P-octabromo-OT^o-tetraphenylporphyrinato Cu(II) (7c) by pyrolysis of C F C 0 N a / C u I . i)toluene-azeotrope, 120 °C, N 3  2  iii)conc. H S 0 , iv)10 % aq. N a H C 0 . 2  4  3  2  ii)150 - 155 ° C , 2 h, N , 2  6 9 smeared and were so close together, isolation of the compounds was not attempted. Evidently, regioisomers and partially substituted preliminary  trifluoromethylation  P-tnfluoromethyl-TPPs existed in the mixture. This p-octabromo-TPP (7c)  using  led the author  to use  P-tetrabromo-TPPs (45b, 45c, and 45d) as precursors in an attempt to effect a cleaner reaction.  (2) Reactions using MTPPBr  (M = Zn(II), Cu(II), andNi(II))  4  (45b,45c,and 45d)  The previous experiment showed that a significant number of partially trifluoromethylated porphyrins are produced due to reductive dehalogenation of brominated positions, since no bromine  substituents  are left  after  the reaction.  A s a result  o f this  incomplete  trifluoromethylation, various porphyrins, presumably including some regioisomers, are produced. In order to simplify the reaction, the P-tetrabrominated  porphyrins, Zn(TPPBr ) ( 4 5 b ) , 4  Cu(TPPBr ) ( 4 5 c ) , and Ni(TPPBr ) (45d) (Scheme 2-3) were used. The central metal was varied 4  4  in order to investigate the effect of metals upon reactivity in trifluoromethylation. The reaction procedure for trifluoromethylation by the pyrolysis method is as described in Scheme 2-2.  After trifluoromethylation using any of the three metal complexes (45b, 45c, and 45d), the EI mass spectrum of the product mixture showed three mass peaks corresponding to P-bis-, P-tris-  and  P-tetralds(ttifluoromethyl)-^j-o-tettaphenylporphyrins  (M(TPP(CF3))(46), 2  M(rPP(CF))(47), M(rPP(CF))(48) (M = Zn(Ii), Cu(II), or Ni(H)) but T L C analysis (silica gel 33  3 4  plate, CHCl /pet. ether) of the product mixture (for any of Zn(II), Cu(II), and Ni(II)) showed 3  smearing of the spots and did not show separation of 46, 47, and 48. Fortunately, it was found that free-bases (H TPP(CF ) ( 4 6 a ) , H TPP(CF ) ( 4 7 a ) , and H T P P ( C F ) ( 4 8 a ) ) can be well 2  3  2  2  3  3  2  3  4  separated on a preparative silica gel plate. The free-base porphyrins (46a, 47a, and 48a) were thus isolated, after demetalation of the product mixture, by silica gel chromatography (this statement  70  MTPPBr a: M =  (45)  4  2H +  b: M = Zn(ll), c: M = Cu(ll), d: M = Ni(ll) CF C0 Na/Cul toluene/DMF 3  2  i, a  Scheme 2-3.  Trifluoromethylation of P-tetrabromo-«?tfJO-porphyrins (45)  by pyrolysis of  C F C 0 N a / C u I . ^toluene-azeottope, 120 ° C , N , ii) 150 - 155 ° C , N , 1 h iii)conc. H S 0 , 3  2  iv)10%aq. N a H C 0  2  3  2  2  4  71  applies to product mixtures in any complex form of Zn(II), Cu(II), and Ni(II)). Isolated free-base porphyrins H T P P ( C F ) ( 4 6 a ) , H TPP(CF ) ( 4 7 a ) . and H T P P ( C F ) (48a) 2  3  2  2  3  3  low resolution E I mass spectrometry, H and 1  1 9  2  3  F N M R spectroscopy, and elemental analysis.  to a specific structure of H T P P ( C F ) . It is believed that 46a 2  and 46a",  trifluoromethylation CF C0 Na/CuI 3  2  were identified by  N M R spectrum of 46a was difficult because peaks could not be assigned  Assignment of the  regioisomers, 46a'  4  of  3  2  is a mixture of symmetric  which were not separated by chromatography. The results of |3-tetrabromo-OTtfjo-tetraphenylporophyrins  are  summarized  P-tettalds(trifluoromethyl)porphyrin (48a) P-tris(tjifluorometiiyl)porphyrins (46a  in  by  Table 2-1.  The  pyrolysis  of  yield  of  by this method was always low, while (3-bis- and  and 47a)  were produced as major products in about  20 - 40 % yield. Variation of the central metal did not significantly affect the yields. It seems that reductive debrornination is dominant in the reaction and this governs the product distribution.  46a'  46a"  T a b l e 2-1. Results of trifluoromethylation by pyrolysis method . a  a  Starting Material  M  Solvent  Time/h  Product (%)  45b  Zn(II)  45c 45d  Cu(II) Ni(H)  DMF DMF DMF DMF  1 24 1 1  46a(16),47a(29), 48a(2.5) 46a(21), 47a(19), 48a(3) 46a(37), 47a(29), 4 8 a ( 5 ) 46a(28),47a(18),48a(3)  P o r p h y r i n / C u I / C F C O N a = l / 1 6 / 4 0 . Temp. = 150 °C. Yields are calculated based on M(TPPBr ) (45). 3  b  b  2  4  72  In  summary,  the  yields  of  the  separated  P-tettalds^fluoromethyl)-^^-  teteaphenylporphyrin were low by use of the pyrolysis method but isolation of three novel P-trifluoromemylporphyrins (46a,  47a,  and 48a)  which are important for analysis of electron-  deficiency of porphyrin macrocycles was allowed by this experiment. Trifluoromethylation by the pyrolysis method is easy to perform. Specifically, handling of the reagents is facile and the reagents are not expensive. However, this method requires high temperatures (150 °C) in order to generate the active C F C u species and thus Cu(I) assisted substitution is hampered by 3  reductive debromination of the starting material. Consequendy, one drawback of this method is that significant  amounts of partially trifluoromethylated porphyrins are produced. Thus,  trifluoromethylation  under  milder  conditions  was  needed,  especially  for  multiple  trifluoromethylation, in order to avoid unnecessary debromination.  c. Trifluoromethylation by CFfZu generated by the metathesis of trifluoromethylcadmium and CuBr The active trifluoromethyl agent in Cu(I) assisted trifluoromethylation is C F C u , which is 3  common to both the pyrolysis and metathesis methods. A n important difference between the two methods concerns the in-situ generation of C F C u . In the pyrolysis method, C F C u is 3  generated from C F C O N a 3  z  3  and Cu(I) halide at about 150 °C. O n the other hand, in the  metathesis method, C F C u is generated from trifluoromediylcadmium (mixture of (CF ) Cd and 3  3  2  CF CdBr) and Cu(I) halide at — 40 °C (see chapter I, section C.2.). The low reaction temperature 3  required for the metathesis method enables the trifluoromethylation to be performed under milder conditions. The reduced temperature prevents reductive dehalogenation.  (1) Preliminary experiments Trifluoromethylation Ni(TPPBr ) (45d) 4  using H T P P B r 2  4  ( 4 5 a ) , Zn(TPPBr ) ( 4 5 b ) , Cu(TPPBr ) ( 4 5 c ) , and 4  4  with C F C u generated by the metathesis of trifluoromeflrylcadmium and CuBr 3  73  was examined to assess the effect of the central metal upon reactivity. The reaction is shown in Scheme 2-4. According to literature precedence,^ several hours in D M F using compounds H T P P B r 2  and Ni(TPPBr ) 4  39  4  m  e  reaction was conducted at 70 °C for  ( 4 5 a ) , Zn(TPPBr ) ( 4 5 b ) , Cu(TPPBr ) ( 4 5 c ) , 4  4  ( 4 5 d ) . Since the work-up procedure is similar for all of the reactions, the  procedure is only described for the reaction with 45b  as the starting material. After the reaction,  D M F and some of the H M P A were distilled off under reduced pressure. The green viscous residue was diluted with acetone and filtered. E I mass spectrometry of the mixture showed that  ( 4 6 b ) , ZnCTPP^^) ( 4 7 b ) , and Zn(TPP(CF ) ) ( 4 8 b ) , but  it contained not only Za(TPV(CF^  3  also partially brominated and partially trifluoromethylated products (49b, crude yield of compound mixture 49b containing compounds  4  see Scheme 2-4). The  was significant (~ 40 % based on 45b).  After the mixture  46b — 4 9 b was treated with cone. H S 0 and neutralized with 10% 2  aqueous N a H C 0 , free-bases 46a 3  4  - 48a were isolated by silica gel chromatography. Free-bases of  49 could not be isolated because the spots were co-eluted, thus appearing as a broad band. The results are summarized in Table 2-2. The Cu(II) and Ni(II) complexes (45c  and 45d)  were not  very soluble in D M F at 70 °C and thus trifluoromethylation reactions were unsuccessful; no tetralds-trifluoromethyl product was obtained and more than 70% of the starting materials was recovered. Trifluoromethylation using free-base porphyrin (45a) porphyrin 45a  was also unsuccessful. Free-base  was metallated with CuBr under the metathesis conditions and Cu(TPPBr ) 4  precipitated out of solution and also small amount of C u deposition trifluoromethylation using free-base porphyrin (45a) was obtained for Cu(II) porphyrin 45c.  porphyrins. However, even with this 45b implies  that  45b  may  not  be  resulted. Thus,  resulted in a similar product distribution as  Zn(II) porphyrin 45b  in D M F at 70 °C. Thus, Zn(II) porphyrin 45b  (45c)  is more soluble than 45c  and  45d  seems to be the best choice of the four tested  as the starting material, 10 % of it was recovered. This  completely  soluble  under  the  reaction  conditions.  r ( 4 9 ) y  Ph  CF  47  3  Ph  48  S c h e m e 2-4. Trifluoromethylation of P-tettabromo-^-fo-porphyrins by metathesis of CF -Cd*/CuBr/HMPA. i)70 °C, N , 5 h, ii)removal of solvents, iii)filtration, 3  2  iv)conc. H S 0 , v)10 % aq. N a H C 0 * C F - C d = (CF)Cd + C F C d B r . 2  4  3  3  3 2  3  75  T a b l e 2-2. Trifluoromethylation by metathesis using M T P P B r ( 4 5 ) . a  4  Porphyrin  M  45a  2H  Product (%)  b  +  45c(67), 46a(l), 4 7 a ( 4 ) , 48a(0)  45b 45c  Zn(II) 45b(10), 46a(2), 4 7 a ( 8 ) , 48a(l 1) Cu(II) 45c(73), 46a(2), 4 7 a ( 5 ) , 48a(0) 45d Ni(II) 45d(86), 46a(l), 47a(2), 48a(0) Porphyrin 0.16 mmol/CuBr 4 m m o l / C F - C d 4 m m o l / H M P A 4 mL, 70 °C, 5 h, under N . Isolated yields are reported. Partially brominated and partially trifluoromethylated porphyrins are not shown in the table because isolation was not possible. a  3  b  2  P-Tetrakis-trifluoromethyl porphyrin was produced in 11 % yield. This result represents a significant improvement from that observed in the pyrolysis method. However, the yield was still low.  Since significant amounts  porphyrins (49b)  of partially brominated and partially trifluoromethylated  were obtained, the reaction may be slow and long reaction times may be  needed. Usually, trifluoromethylation of halogenated aromatic compounds by metathesis under the  same reaction conditions  on^o-iodotoluene  gives moderate  yields (e.g.  to on$o-tjifluoromethyltoluene)133  j  n  thi  76 % for the  s  W O  rk,  conversion  of  trifluoromethylation is  required to occur in a sterically hindered region (P-pyrrolic positions are located between two phenyl groups and adjacent to each other) and the reaction may thus be slower than usual trifluoromethylation using simple substrates such as iodotoluene. Consequendy, either longer reaction times or higher reaction temperatures  may be necessary in order to  facilitate  trifluoromethylation with the same molar ratio of the reactants. Thus, optimization using Zn(TPPBr ) (45b) 4  in metathesis induced trifluoromethylation at different reaction times and  temperatures was investigated.  76  (2) Optimisation of theyieldfor B4etrakis(trifluoromethyl)-meso-tetraphenylporphyrin As described in the previous section, trifluoromethylation of Zn(TPPBr ) (45b) 4  under the  conditions shown in Scheme 2-4 showed significant amounts of partially brominated and tnfluoromethylated porphyrins, presumably due to steric hindrance. The first part of this section describes  investigations  concerning  the  effects  of  reaction  times  upon  the  yield  of  P-tettakis(tiifluoromemyl)-OTWo-tetJraphenylporphyrin by the metathesis methodology.  The reaction time was extended to 88 h with all other reaction conditions shown in Scheme 2-4 remaining constant. During the reaction, changes in the UV-visible spectrum were monitored. As shown in Figure 2-1, the spectrum of an aliquot of the reaction mixture diluted in C H C 1 changed considerably with time. The Soret band (430 nm) of 48b 2  had  2  (trace A in Figure 2-1)  shifted to 448 nm and a maximum of a broad Q band was at about 700 nm after  4 h (trace C). After 48 h, the Soret and the maximum of the broad Q band was seen to have gradually blue-shifted and settled at 438 nm and 660 nm, respectively (trace F). There was a large shoulder around 460 nm. There was no change after 48 h (trace F (48 h), G (68 h), and H (88 h)). Trace I in Figure 2-1 is the spectrum of the required product Zn(TPP(CF))(48b) in 34  CH Cl2 and trace J is 48b 2  in CHjCL^ containing ~1 % (v/v) H M P A . Spectrum J has maxima at  448 nm and 724 nm, with a large broad shoulder at 462 nm, which is attributed to the presence of H M P A by comparison to the spectrum F, G, and H. After 88 h, the reaction mixture was subjected to an acidic work-up (TFA-CH^CL) to effect demetallation of the products. Analysis by  F A B mass  spectrometry  indicated  that  the  product  mixture  contained  perfluoroalkylporphyrins as shown in Table 2-3. The mass of compound 50a that of H T P P ( C F ) (47a) 2  3  3  several  is different from  by 50, which agrees with the mass of - C F - (= 50.0). It is conjectured  that the presence of compounds 50a,  2  51a,  52a,  53a,  54a,  and 55a  originates from the  77  00  CO  350  400  450  T  1  1  1  500  550  600  650  r  700  750  800  Wavelength/nm  F i g u r e 2-1. UV-visible spectra during trifluoromethylation of 45b at 70 °C. A: 45b, B: 15 min, C: 4 h, D: 20 h, E: 25 h, F: 48 h, G: 68 h, H: 88 h, I: 48b,  J: 48b  + HMPA..  78  introduction of extended perfluoroalkyl chains into the porphyrin (see eq.(1.3) and (1.4), p.37). Similarly, a mass difference of 50 is seen among 48a, 51a.  The structure of 52a  54a,  and 55a is uncertain.  T a b l e 2-3.  54a,  and 55a  and between 50a  is shown below but the regiochemistry of porphyrins 50a,  51a,  and 53a,  Products obtained by the reaction at 70 °C for 88 h Products  H TPP(CF )  Mass(obsd)  a)  (47a)  820 888 H TPP(CF ) (48a) 870 50a 920 51a H TPP(CF CF )(CF ) (52a) 938 970 53a 988 54a 1038 55a Low resolution F A B mass spectrometry. 2  52a,  2  3  3  2  3  4  2  3  3  Mass(calcd for)  Relative Intensity  818.7(C H F N ) 886.7(C H F N ) 868.8(C H F N ) 918.8(C H F N ) 936.8(C H F N ) 968.8(C H F N ) 986.8(C H F N ) 1036.8(C H F N )  24 80 37 36 100 21 81 21  47  27  9  48  26  12  4  n  4  48  3  27  4  49  27  13  4  49  26  14  4  50  27  15  4  50  26  16  4  51  26  18  4  Separation of the perfluoroalkylated porphyrins was attempted. A patient and agonizing search for a suitable solvent system for T L C analysis found a solvent system to separate these porphyrins as shown in Table 2-4. The major products 48a,  52a,  and 54a  a silica gel chromatographic plate using benzene/cyclohexane/acetone= Due to the small amounts present, products 50a, the T L C plate. After 48a  51a,  53a,  and 55a  could be separated on 6/3.5/0.5 (Table  2-4).  could not be clearly seen on  and 52a were isolated, a weakly colored (orange) band was left near the  top of the column. This colored band could not be flushed out with polar solvents such as M e O H or acetone. Unfortunately, 54a  could not be isolated. Presumably, it decomposed on the  79  silica gel column during the chromatographic separation of 48a  and 52a.  Isolated 48a  and  52a  were identified by ' H and F N M R spectroscopy, E I mass spectrometry, and elemental analysis. 1 9  T a b l e 2-4. R values for metal-free perfluoroalkylated porphyrins f  Solvent System CH Cl :hexane =3:7  C H :cyclohexane:acetone =6:3.5:0.5  46a  0.57  -  47a 48a 52a 54a  0.29  -  0.09  0.38  0.09  0.27  0.09  0.18  2  2  6  6  Porphyrin  a)  a)  Mixture of regioisomers.  b)  b)  Smears.  The yield of the required porphyrin H T P P ( C F ) (48a) 2  3  4  was 13 % (Table 2-5). This result  was similar to that obtained by trifluoromethylation at 70 °C and 5 h (see Table 2-2) but the yield of H T P P ( C F C F ) ( C F ) (52a) 2  2  3  3  3  was 22 % (Table 2-5). This product was not obtained after the  reaction of 5 h duration. Since partially brominated and partially trifluoromethylated porphyrins were not detected in the product mixture by F A B mass spectrometry, the reaction time (88 h) was evidently long enough to allow complete exchange of the bromine by nucleophiles. However, it seems that exchange of - B r and —CF groups is slow and the C F 3  3  nucleophile is  lost due to extension of perfluoroalkyl anions (eq.(1.3) and (1.4), p.37). Thus, nucleophilic attack by oligomerized perfluoroalkyl anions rather than the trifluoromethyl anion is increased, giving porphyrins with oligomerized perfluoroalkyl groups.  In summary, extension of the reaction time to 70 °C facilitated exchange of - B r with perfluoroalkyl groups but the product distribution was found to be complex due to extension of the  perfluoroalkyl chain. 133  Separation  and  purification  of  the  complex  mixture  of  80  P-trifluoroalkylated porphyrin products were found to be extremely difficult and not wholly successful despite intense efforts.  Reactions were also run at higher temperatures in order to investigate the effect of temperature on the product distribution and yield.  Figure 2-2 shows the UV-visible spectra observed for trifluoromethylation at 110 °C under otherwise identical conditions to those shown in Table 2-2. In this reaction, the peak of the Soret band of 45b  was observed at 448 nm at 15 min (trace B).  between l h (C)  and 2 h (D).  A t 4 h (E),  The spectra remained unchanged  a split of the Soret band was observed. A t 6 h (F),  the  Soret was a single band at 434 nm and there was little change in the spectra afterwards (8h (G) and 21 h (H)).  Unlike the case for the reaction at 70 °C, the shoulder around 460 nm is not  prominent after reaction completion (compare Figure 2-1, H to Figure 2-2, H).  The final  position of the Soret band was 4 nm shorter than that of the reaction at 70 °C and the final U V visible spectrum seems quite different to traces I and J.  E I mass spectrometry of the final  reaction mixture contained neither partially brominated porphyrins nor the porphyrins with extended perfluoroalkyl chains. The product mixture contained only bis-, tris-, and tetrakistrifluoromethyl Zn(II) porphyrins (46b,  47b,  and 48b).  After demetallation, the porphyrin  mixture was purified by column chromatography on silica gel to give the isolated products H T P P ( C F ) (46a) 2  3  2  (13 %),  H T P P ( C F ) (47a) 2  3  3  (12 %),  and  H T P P ( C F ) (48a) 2  3  4  (17 %).  Dehalogenation of halogenated aromatic compounds in D M F is known. 187  The reaction was also run at 90 °C and isolation of the final products in free-base form was performed. Isolated products of the several reactions with different temperatures and times are summarized in Table 2-5.  F i g u r e 2-2. UV-visible spectra during trifluoromethylation of 45b at 110 °C. A: 45b, B: 15 min, C: 1 h, D: 2 h, E: 4 h, F: 6 h, G: 8 h, H: 21 h, I: 48b, J: 48b  + HMPA.  82  At low reaction temperatures, extension of perfluoroalkyl chains occurs giving significant amounts of H T P P ( C F ) ( C F C F ) ( 5 2 a ) . A t high reaction temperatures the yields of P-bis- and 2  3  3  2  3  P-teis(trifluorometliyl)porphyrin (46a  and 47a)  increase and 52a  is not isolated. As shown in  Table 2-5, the several-hour reactions at 90 °C resulted in the best yields of the required  P-tetrakis(difluoromethyl)porphyrin ( 4 8 a ) .  T a b l e 2-5. Isolated P-perfluoroalkyl-^gJo-tetraphenylporphyrins. Temp.(°C)  Time (h)  70 90  88 7 5 21 8  110  In  summary,  trifluoromethylation  the of  pyrolysis P-octabromo-  Isolated porphyrin(%)  46a  47a  48a  52a  9 11 13 16  5.6 21 24 12 13  13 38 42 17 20  22 10 8  method  was  not  appropriate  for  the  effective  and P-tetrabromo-/»wo-tetraphenylporphyrins.  Only  complex mixtures and low yields of P-tiifluoromemyl-w^o-tettaphenylporphyrins were obtained using P-octabromo-w^-tetraphenylporphyrin as a starting material. The reactions P-tetrabromo  metalloporphyrins  yielded  P~bis-  or  using  P-tris (trifluoromethyl) -meso-  tetraphenylporphyrins as major products and P-tettalds(tjifluoromethyl)porphyrin was obtained in very low yields. The reaction conditions, especially the high temperature (150 °C), were found to be too severe for multiple trifluoromethylation using P-octabromo or P-tetrabromoporphyrins and reductive debromination seemed to dominate under these conditions.  Trifluoromethylation by C F C u generated by the metathesis of tofluoromethylcadrnium 3  and CuBr can be performed under relatively milder reaction conditions. However, the highest  83  temperature reported for this reaction (70 °C)133 as not sufficiently high for effective multiple W  trifluoromethylation of p-tettabromo-wwo-tetjraphenylporphyrins.  Longer reaction times at 70 °C  increased the yields of higher fluorinated alkyl species, which attack the brominated p-pyrrolic positions to yield porphyrins with extended perfluoroalkyl chains such as 50a - 55a.  Reactions at  110 °C did not give such porphyrins but higher yields of porphyrins 46 and 47 were obtained due to reductive debromination. Thus, the yields of P-tettalds(ttifluoromethyl)porphyrin 48 were maximized for the reaction at 90 °C for 5 h.  The UV-visible spectra obtained during trifluoromethylation via the metathesis method showed significant red-shifts of the peaks in the early stage of the reactions (Figure 2-1 and Figure 2-2), and for the reaction at 110 °C red-shifts were followed by blue-shifts of the peaks (Figure 2-2). It is known that porphyrin plane distortion induces red-shifts of UV/visible absorption bands (see Chapter 1, section D./.b.).144-147  Steric interaction between the adjacent  pyrrolic P-substituents was analyzed by computer modeling. Figure 2-3  shows geometry  optimized 3,4-dibromopyrrole and 3,4-bis(trifluoromethyl)pyrrole (2,5-hydrogens were omitted) by molecular mechanics.188 According to the calculation, the —C F  groups are closer to the  3  pyrrole ring than the —Br groups and the van der Waals radius of —CF is much larger than that 3  of —Br. The distance between the two —Br centers (3.645 A) is comparable to the sum of the two - B r vdw radii (3.90 A). O n the other hand, the C - C distance between the two - C F  3  groups  (3.273 A) is much smaller than the sum of the two - C F vdW radii (5.66 A). Since rotation of the 3  —CF presumably occurs, steric interaction between the two —CF groups may be seriously large. 3  3  Keeping this in mind, the author attempted to rationalize the unique shifts of peaks of the U V visible spectra during trifluoromethylation (Scheme 2-5). In the early stage of the reactions, the partially brominated and trifluoromethylated porphyrins such as mono-trifluoromethylated  84  v d W ( B r ) = 1.95 A  C - F = 1.492 A v d W ( F ) = 1.35 A . w d W (CF3) = 2.83 A  F i g u r e 2-3. 3 , 4 - D i b r o m o p y r r o l e and 3,4-bis(trifluoromethyl)pyrrole m o d e l e d by H y p e r C h e m .  1 8 9  T h e van der Waals (vdW) radii o f B r and F were  obtained f r o m ref.123 and the v d W o f C F was calculated f r o m the C - F b o n d 3  length and the v d W (F).  8 5  86 ZnTPPBr (CF ) or bis-tofluoromethylated Z n T P P B r ( C F ) may be produced fairly easily but 3  3  2  3  2  introduction of the bulky - C F groups presumably forces the macrocycle to distort to some 3  degree. Macrocycle distortion will cause red-shifts of the absorption bands in the UV-visible spectrum. 144-147 j j conjectured that a problem starts after introduction of the second —CF t  s  3  group. Since the steric interaction between the adjacent - C F groups on a pyrrole is severe as 3  shown in Figure 2-3, introduction of the third and the fourth - C F should be much more 3  difficult (slower) than that of the first two. The measures taken in order to overcome this steric encumberance were to extend the reaction time and to raise the reaction temperature. For extended reaction times at 70 °C, more of the extended perfluoroalkyl chains are introduced onto the porphyrins and complete trifluoromethylation is hampered by extension of perfluoroalkyl chain.  O n the  other  hand,  at  110 °C  reductive  debromination  prevents  effective  trifluoromethylation. The reactions at 90 °C gave the best yield (-40%) of Zn(TPP(CF ) ) 3  4  (48b)  of the three temperatures. However, difficult chromatographic purification was still required in order to obtain pure P-tetraltis(rjifluorometliyl)-OTtfj'o-teteaphenylporphyrin  ( 4 8 a ) . Nevertheless,  the optimized trifluoromethylation reaction produces the required porphyrin 48a in a sufficient yield to continue further studies. The yield of required 48a could also be improved by increasing the amount and concentration of C F C u but the effect of molar ratio of the reactant on the 3  product yield was not investigated.  In the demetallation process following trifluoromethylation, CuBr must be completely removed. This is because treatment of the product mixtures containing 48a with acid in the presence of CuBr gives an unidentified orange compound. A s shown in Figure 2-4, a broad Soret-band-like peak appeared at 420 nm and no Q bands were observed in the UV-visible spectrum of this orange compound. This phenomenon was checked with pure 48a  in the  350  450  550  650  750  850  950  Wavelength (nm)  F i g u r e 2-4. UV-visible spectra of the orange compound (dark line) and HTPP(CF)(48a) (narrow line). 2  34  88 presence of CuBr in acidic (TFA) C H C 1 and indeed the orange compound was obtained. 2  Porphyrin 48a  2  seems to be reduced to the orange compound by the electron produced by the  presence of CuBr in acidic conditions, thus causing a significant decrease of the final product yield. This phenomenon was also observed with H T P P ( C F C F ) ( C F ) ( 5 2 a ) . This phenomenon 2  2  3  3  3  can be avoided by careful removal of CuBr (for example tofluoromemylporphyrins in metallated forms are very soluble in acetone, CH C1 , or CHC1 but CuBr is not. Thus after the reaction, 2  2  3  dried product mixtures were dissolved in acetone and CuBr could be filtered off before demetallation. Although further investigation to study the mechanism of reduction was not attempted since the orange compound could not be identified, sensitivity of these porphyrins to reducing reagents will also be shown in section AJ. and B.5.a.(2).  2. Methylation (3-Methyl-wwo-tetraphenylporphyrins were required in order to compare the electronic and structural effects of these porphyrins with the trifluoromethyl analogues. P-tettabromo-^j-o-tettaphenylporphyrin Zn(II) complex (45b)  Methylation of  was performed by Cu(I) assisted  methylation involving the use of C H L i and Cu(I) halide. 1^9 As shown in Scheme 2-6, 45b 3  was  treated with an excess of Li(CH ) Cu at 32 - 33 °C for 24 h, which was formed by the reaction of 3  2  C H L i and CuBr at - 80 °C in ether. Oligomerization as observed for trifluoromethylation of 3  P-tetrabromoporphyrin by metathesis did not occur in this case. After the coupling reaction, the remaining bromo substituents were removed by reflux in D M F in the presence of CuBr under air for 2 h. Since the major purpose was to obtain P-methylporphyrins but not to analyze the methylation reaction products, brominated sites were eliminated in order to simplify separation of  P-methylporphyrins. Formation of  confirmed  by  EI  mass  p-methyl-^jo-tetraphenylporphyrins (57b  spectrometry.  The  solubility  of  the  Zn(II)  - 59b)  complexes  was of  Z n T P P (2b)  58b  59b  iii, iv  T 2a (32 %), 56a (0.5 %), 57a (19 %), 58a (17 %), 59a (15 %)  S c h e m e 2-6.  Methylation of  45b. i) E t 0 , 32 ° C , 24 h, ii)CuBr, D M F , reflux, 2 h, 2  iii)TFA, reflux, 1.5 h, iv)10 % aq. N a H C 0 . a = 2 H , b = Zn(II) +  3  90  p-methylporphyrins (ZnTPP(CH ) ( 5 7 b ) , ZnTPP(CH ) ( 5 8 b ) , ZnTPP(CH ) ( 5 9 b ) ) was low in 3  2  3  3  3  4  CHC1 , C H C 1 and benzene, while the free-bases showed moderate solubility in those solvents. 3  2  2  Thus, separation by chromatography on silica gel was performed with the metal-free porphyrins (H TPP(CH ) ( 5 7 a ) , H TPP(CH ) ( 5 8 a ) , H TPP(CH ) ( 5 9 a ) ) . The isolated yields are shown in 2  3  2  2  3  3  2  3  4  p-Mono(methyl)-w^-tetraphenylporphyrin (H TPP(CH )) (56a)  Scheme 2-6.  2  (2a)  and H T P P  3  2  were also obtained in 0.5 % and 32 % yield, respectively. As found for trifluoromethylation products, P-bis(methyl)-OTtfj-o-tetraphenylporphyrin (57a)  is formed as a mixture of regioisomers  which were not separated.  In summary, methylation of the P-tetrabromo-wwo-tetraphenylporphyrin zinc complex by CH Li  and  3  CuBr  (Li(CH ) Cu) 3  tetraphenylporphyrins (59a) amount of isolated 59a  was  2  The  were obtained in 15 % yield.  required  P-tetramethyl-w^o-  The yield was low but since the  was sufficient for analysis to compare with P-tetrakis(trifluoromethyl)-  OTtfjo-tetraphenylporphyrin ( 4 8 a ) , porphyrins (57a  achieved.  and 58a)  this reaction  was  not  optimized.  Two  other  P-methyl  were also obtained, which enabled a study of a series of compounds.  3. Metallation MetaUation of H T P P ( C F ) (48a) 2  3  4  with Zn(H)/Co(H)/Fe(Iir) is described to give the  corresponding complexes. The Zn(II) and Co(II) complexes were to be used in electrochemical studies  and  in  Zn(TPP(CF ) ) (48b) 3  4  the  study  of  axial  ligand  binding  by  spectrophotometric  was synthesized by trifluoromethylation of Zn(TPPBr ) (45b) 4  titration.  as described  in the previous section. However, pure p-tettalds(trifluorometJiyl)-OTtfj"o-tetJ:aphenylporphyrin could only be obtained by chromatography of the free-base 48a. subsequently obtained by re-metallation of 48a.  Thus, complex 48b  was  The Fe(III) complex is important for models for  91 cytochromes P-450s since the enzymes contain protoporphyrin I X Fe(III) complex in the functional site.  a. Synthesis of Zn(II) and Co(II) complex of 48 Insertion of Zn(II) and Co(II) into 48a  was found to be straightforward. As shown in  Scheme 2-7, 2.5-3 eq. (excess amount of metal salts were used to ensure complete metallation) of  CF  3  Ph  MTPP(CF ) 98 %, 48b: M = Zn(ll) 96 %, 48e: M = Co(ll) 3  S c h e m e 2-7.  Insertion of Zn(II) and i)Zn(OAc) .2H 0 or C o C l , M e O H - C H C l , 2  2  Co(II)  into  4  H TPP(CF ) 2  3  ( 4 8 a ) .  4  2  a solution of Z n ( O A c ) - 2 H 0 (or CoCL) dissolved in M e O H were added to a CHC1 solution of 2  free-base porphyrin  2  3  ( 4 8 a ) . For the reaction with the Zn(II) salt, the color of the brown  suspension of the free-base porphyrin instantly changed to bright green at room temperature upon addition of Zn(OAc) dissolved in M e O H . The color change was easily observed by U V 2  visible spectroscopy (UV-visible spectra will be shown later in this chapter). For the reaction with the Co(II) salt, formation of the complex was observed by a color change from brown to bright green upon heating the mixture on a steam bath. Since the ligand was known to be pure, purification required only removal of excess metal salts which was easily done by washing the CHC1 solution of the complexes with water and drying over anhydrous N a S 0 . The yields for 3  2  4  92  48b  and 48e  were 98 and 96 %, respectively. Formation of 48b  and 48e  was confirmed by  elemental analysis, mass spectrometry, and H and F N M R spectroscopy. J  1 9  b. Synthesis ofFe(III) complexes of 48 and 52 Usually, Fe(III) complexes of porphyrins are made by insertion of Fe(II) into the macrocycle followed by aerobic autoxidation of Fe(II) to Fe(III). conducted  using  solution)69,163  m  FeBr i9o 2  a  c  e  u  c  or  FeCl i9i  in  2  69  Typically the reactions are  dry T H F , F e S 0 - 7 H 0 4  2  (saturated  acid/pyridine, or Fe(OAc) (Fe powder in hot acetic acid) 2  69  aqueous in acetic  acid. The insertion reaction must be initially performed under A r or N , followed by exposure of 2  the reaction mixture to air after the Fe(II) insertion, thus allowing oxidation to Fe(III). In some cases Fe(0) (from Fe(CO) ) can also be inserted to give Fe(III) complexes.I ,192 63  5  As shown in  path  A  of Scheme 2-8(a), all of these routes were attempted but synthesis of  the Fe(III) complex of 48a porphyrin (48a) free base 48a)  proved to be unsuccessful. In each case when the free-base  was mixed with the Fe(II) or Fe(0) reagent, the solution (initially brown due to became orange, and showed a broad single band at 418-420 nm in the UV-visible  spectrum in CH C1 . This spectrum was identical to the one obtained from 48a 2  2  + CuBr under  acidic conditions (chapter 2 section A . / . , Figure 2-4). The same spectrum was obtained when the free-base (48a)  was treated with aqueous L-ascorbic acid (we employed this reducing reagent  since ascorbic acid is a well-known reducing reagent for the reduction of transition metal cations such as Fe(III)l ). Assuming that the orange compound was a reduced form of the free93  base 48a by reaction with Fe(0), Fe(II), ascorbic acid, or Cu(I), the orange compound was treated with an oxidizing reagent such as dilute H O (5-10 %) in C H C 1 but the UV-visible spectrum of 2  2  2  2  the orange compound did not return to that of the free-base. Thus, it was found that 48a is very  93  Orange c o m p o u n d  Ph  (b)  Ph-<  S c h e m e 2-8. Synthesis o f F e C T P P ( C F ) ) C l (48f) 3  4  Br  /FeOIIJ^-Ph  and F e ( T P P B r ) C l 4  ( 4 5 e ) .  i ) F e C l , T H F , reflux, 2 h(Ar), 2 h(air); F e , H O A c , 1 0 0 ° C , 2 h(Ar), 2 h(air); or 2  F e ( C O ) , 1 , 6 0 ° C , 5 h(Ar),rt, 12 h(air), i i ) L i N ( S i M e ) , T H F , r.L, A r , i i i ) F e C l , 5  2  3  2  2  5 0 ° C , 5 m i n ( A r ) , r.t., 2 h(air), iv)neutral alumina c h r o m a t o g r a p h y - C H C l , v)6 3  M aq. H C 1 , v i ) T H F - 2 0 % aq. K O H , r.t, 2 h, air.  94  sensitive to reduction to give an unidentified orange compound which is not itself easily oxidized. For comparative purpose, a Fe(III) complex was prepared using H T P P B r (45a) 2  the free-base 45a  4  but  did not suffer reduction under these conditions.  In order to facilitate the insertion of Fe(II), and avoid the irreversible reduction of followed; firstly the N - H protons  path B of Scheme 2-8(a) was  of the  48a,  free-base were  deprotonated by treatment with lithium bis(tjtimethylsilyl)amide (LiN(SiMe ) ) to yield the lithium 3  complex  of the porphyrin (60),  1  2  then this was reacted with F e C ^ . ^  9 4  successfully gave the final product, Fe(TPP(CF ) )Cl 3  4  This method  3  ( 4 8 f ) , in 56 % yield after purification. The  rationale for why reduction of the porphyrin did not occur in this case is probably due to a change of the reduction potential of the macrocycle by replacement of H ionization energies of H and I i are 13.60 eV and 5.32 eV respectively,! ^ 9  with L i . The first  +  +  j^  a n c  u  s  H  +  should be  more electron-withdrawing than L i and the reduction potential of the macrocycle should +  decrease (harder to reduce) by replacement of H with L i . In the purification process (step iv in +  Scheme 2-8(a)), the p-oxo dimer (61)  +  was formed on the neutral alumina chromatographic  column. The p-oxo dimer was then converted to 48f  by washing 61 in C H C 1 with 6 M HC1. 2  Compound 61 can also be produced by treatment of 48f Scheme 2-8(a). Similarly, Fe(TPP(CF ) (CF CF ))Cl (52c) 3  3  2  3  with an alkali solution (step vi in (not  shown  in Scheme 2-8)  obtained in 76 % yield after purification. As shown in Scheme 2-8(b), for 45a, reported F e C l / T H F method^ !, 9  2  Fe(TPPBr )Cl (45e) 4  Fe(OAc) in 2  2  was  in addition to the  acetic acid also worked well to prepare  in 92 % yield. Compounds 48f,  52c,  and 61 were characterized using E I  mass spectrometry and ' H and F N M R spectroscopy. The ' H N M R spectrum of 48f 1 9  and  52c  showed a broad singlet at 77 ppm and a broad multiplet at 74 ppm respectively, which are similar chemical shifts to that of 74 ppm observed for the P-pyrrolic protons of Fe(TPPBr )Cl (45e) 4  and  95  that of 79 ppm observed for Fe(TPP)Cl (2d).  These large downfield chemical shifts of the  P-pyrrolic protons are indicative of high spin (S=5/2) Fe(III) porphyrins.191,196  Thus, with compounds Fe(TPP(CF ) )Cl (48f) 3  and Fe(TPP(CF ) (CF CF ))Cl (52c)  4  3  3  2  3  in hand  analysis and comparison studies could be continued.  4. Summary T o conclude, P-trifluoromethyl and P-methyl porphyrins have been prepared from p-tetrabromo-porphyrin. Zn(TPP(CF ) ) (48b) 3  4  Fe(III) complex of P-tetrakis(trifluoromethyl)-  and Co(TPP(CF ) ) ( 4 8 e ) . Preparation of the 3  and  4  P-tiis(tjifluoromemyl)(pentafluoroethyl)-  porphyrins was found to be more problematic, but eventually Fe(TPP(CF ) )Cl (48f) 3  Fe(TPP(CF ) (CF CF ))Cl (52c) 3  3  2  3  4  and  could be obtained in moderate yields.  Further research into the synthesis of these compounds must focus on increasing the yields. For the trifluoromethylation reaction, the effect of molar ratio of the reactants may be investigated. For methylation, palladium-catalyzed cross coupling reaction may be a useful alternative method.197,198 phe yield of the Fe(III) complex of P-tetrakis(trifluoromethyl)porphyrin (481)  may be improved indirecdy by understanding the mechanism of reduction of the  free-base porphyrin, which was the major problem in preparation of the complex.  B. A n a l y s i s of P t r i f l u o r o m e t h y l w e s o t e t r a p h e n y l p o r p h y r i n s As described in Chapter I, the porphyrin macrocycle shows characteristic UV-visible, N M R spectroscopic, and redox properties due to the 7t-conjugated electron system. The strong electron-withdrawing effect of the —CF group introduced onto the macrocycle affects the 3  electronic property of the macrocycle. Thus, the first point of investigation is the electronic  96  structures of the novel P-teifluoromethylporphyrins. One of the main objects of section B is to describe the investigation regarding this point by the UV-visible, N M R spectroscopy, cyclic voltammetry, and X-ray crystallography.  Since —CF is also a bulky group, the second point of investigation is a structural change of 3  the macrocycle imposed by introduction of —CF groups. In order to achieve this goal the steric 3  effect  of  -CF  3  groups  on  the  macrocycle,  p-tettakis(trifluoromethyl)porphyrinato Zn(II) examined  and  (Zn(TPP(CH ) ) 3  Scheme 2-1),  4  compared  with  ( 5 9 b ) , Scheme 2-6),  and other  X-ray  (Zn(TPP(CF ) ) 3  those a  the  of  4  a  crystal  structure  ( 4 8 b ) , see  Scheme  of  2-7)  a is  P-tetramethylporphyrinato Zn(II)  p-tetrabromoporphyrinato Zn(II)  reported metalloporphyrins such  as  (Zn(TPPBr ) 4  Zn(TPP) (2b)  ( 4 5 b ) ,  (Figure 1-8).  Rationalization of characteristic UV-visible and N M R spectra of P-trifluoromethylporphyrins in terms of the steric effect as well as the electronic effect of —CF was also attempted. 3  Our  tliird  point  of  investigation  is  the  electron-deficiency  of  the  novel  P-trifluoromethylporphyrins. Electron-deficiency and affinity can be discussed in terms of the redox properties of the macrocycles, although the pure electronic effect of substituents can be hampered by a structural change of the macrocycle as discussed in Chapter I, section D . Z b . Accordingly, in order to assess the electron-deficiency of P-tetrakis(tri.fluoromethyl)porphyrin from view points other than the macrocycle redox properties, determination of the piC, for the first deprotonation of pyrrolic N - H of p-tettalds(trifluoromethyl)porphyrin and determination of the  stability  constants  for  pyridine and imidazole  p-tettalds(tiifluoromethyl)porphyrin  Co(II)  complex  binding to  the  central Co(II)  by spectrophotometric  of  titration were  performed. The reason that Co(II) complex was chosen as the porphyrin system and pyridine  97  and imidazole as ligands is that homologous systems have been studied using a few electrondeficient  porphyrins.  The  resulting  evaluation  of  electron-deficiency  of  P-tettakis(tofluoromemyl)-porphyrin can be easily done by comparing this system with other reported electron-deficient porphyrin systems.  Details of the analysis are described in the following sections.  /.  UV-visible spectra of synthesized novelporphyrins The main purpose of this section is to analyze the electton-withdrawing effect of  trifluoromethyl groups  on the  tettaphenylporphyrins.  electronic  The  three  2  3  see Chapter II,  4  synthetic  novel  2  3  p-trifluoromethyl-w^o-  porphyrins,  (H TPP(CF ) ( 4 6 a ) ,  tetrakis(trifluoromethyl)porphyrins H T P P ( C F ) (48a)  structure of the  P-bis-,  tris-,  H TPP(CF ) ( 4 7 a ) ,  2  2  3  3  and  section A) are the subject of the investigation. The first part  of this section concerns the UV-visible spectra of the novel P-trifluoromethylporphyrins in the free-base  form.  The  UV-visible  H T P P (2a) (Figure 1-8),  spectra  of  these  H T P P B r (45a)(Scheme 2-1),  2  2  4  are  compared  with  those  P-methylporphyrins ( 5 6 a 5 9 a )  and  (Scheme 2-6) and the similarity of the spectra of H T P P ( C F ) ( 4 7 a ) , H T P P ( C F ) (48a) 2  3  of  3  2  3  4  and  p-tris(trifluoromethyl)(pentafluoroethyl)porphyrin (H TPP(CF ) (CF CF ) ( 5 2 a ) , p.78) to that of 2  3  3  2  3  bacteriochlorin (64) (p. 108) is to be discussed. The second part of the section describes the concentration  effect  on  the  UV-visible  spectral  change  of  H T P P ( C F ) (48a) 2  3  4  and  H TPP(CF ) (CF CF ) ( 5 2 a ) , since there is a concern that electron-deficient porphyrins may have 2  3  3  2  3  high tendency to aggregate (see Chapter I, section D J.b.).  In the second part of the section the UV-visible spectra of the Zn(II), Co(II), and Fe(III) P-tettakis(trifluoromethyl)porphyrins are compared with known metalloporphyrins and the some  98  tendencies commonly observed through the novel P-tettakis(trifluoromemyl)metaUoporphyrins are described.  a. Free-base porphyrins (1) UV-visible spectra in CH Cl 2  2  In this section UV-visible spectra of the free-base porphyrins in one of the most common solvents for porphyrins, CH C1 , are shown and effects of - C F groups on the electronic and 2  2  3  steric properties of the porphyrin macrocycle are discussed.  UV-visible absorption maxima of free-base  ^j-o-tetraphenylporphyrins  P-substituted  together with reported electron-deficient porphyrins are summarized in Table 2-6. All porphyrins except for H ( C F ) P (16a, 2  3  n=l) (Figure 1-8, p. 11) are «?«o-tetraphenylporphyrins. As observed  4  along with introduction of other electron-withdrawing groups onto H T P P (2a)  (Figure 1-8) (e.g.  2  2a -> large  H T P P B r (45a)(Scheme 2-1) or 2a 2  red-shifts  of  absorption  p-trifluoromethylporphyrins (Scheme 2-2)  H T P P ( C N ) (32a,  4  maxima  H TPP(CF ) 2  3  and H T P P ( C F ) , ( C F C F ) 2  P-methylporphyrins  3  2  H TPP(CH ) 2  2  3  2  3  2  x=4) (Figure 1-20, p.51)), 1 8 5  4  were  observed  for  the  series  ( 4 6 a ) , H TPP(CF ) ( 4 7 a ) , H TPP(CF ) 2  (52a)  3  3  2  3  4  of  (48a)  ( p . 7 8 ) . O n the other hand, the series of  ( 5 7 a ) , H TPP(CH ) ( 5 8 a ) , and 2  3  3  (Scheme 2-6) showed insignificant red-shifts from that of H T P P (2a). 2  H TPP(CH ) 2  3  4  (59a)  These observations  indicate that the electronic structures of P-tjrifluoromethylporphyrins were significantly changed from  that  of  2a  but  those  of  P-methylporphyrins  OTWO-tettalds(tofluoromemyl)porphyrin39 (H (CF ) P (16a, 2  3  4  were  not.  Interestingly,  n=l)) (Figure 1-12, p.29) shows blue-  shifts of the Soret and of the two of the four Q bands in spite of having four - C F groups. Thus, 3  99  CN  SO CN  SO 00  cn,  cn, so oo so  rn. ^ m so m so r-  OO SO T f  SO  cn  PO  ^-H  T£, CN CN  Tf^  CN  cn oo  m rrn,  so cn  CN  cn  CN  Tf,  Tf,  so  T3  a  CO ON  m  o  so  m  SO  SO  CN  so  m c<S,  O  o  so  a!  HO  CO  m  00  oc?  cn cn^ C/3  o  ON  m  CN  C J T f  m  cn  CN CN  T f  T f  00  SO  so  T f  [-OO  CN  SO  CN O  1  T f  00  Q0 0 .  cn^ cn CN m  oON  SO  R  cn,  cn,  in m  oo m  cn^ t-t-m  cn. so 00 in  cn. so T f in  cn^ m T f m  ON  T f  T f  CN  m  m  ON  SO  o so CD, o  in  CD  1  m  CN  r~oo  ON  m cn  CN  ON  00  o  ON  SO  00  in m  CN  cn m  m  SO  T f  SO  so cn^ cn^  cn, so T f so  ON  so  00  ON  CN  o  CN  p  so  so  T f  o  cn.  m co,  T f  m.  so" cn  TP  o  fit  oo  00  T f  CN  CN  cn.  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CJ,  CJ,  PH  PH  cN  E  CN  E  O  o  100  the positions of electton-withdrawing groups or the symmetry of the porphyrin and strong electron-withdrawal of the substituents affect the electronic structure of the macrocycle. U V visible spectra of H T P P ( C F ) 2  room  temperature  H TPPBr 2  4  (45a)  H TPP(CH ) 2  3  3  are  2  ( 4 6 a ) , H TPP(CF ) ( 4 7 a ) , and H T P P ( C F ) (48a) 2  shown  and  in  3  Figure 2-5.  (3-methylporphyrins  3  2  For comparison, (H TPP(CH ) 2  3  2  3  4  UV-visible  in C H C 1 at 2  spectra  2  of  ( 5 7 a ) , H TPP(CH ) ( 5 8 a ) , 2  3  3  ( 5 9 a ) ) are shown in Figure 2-6 and Figure 2-7 respectively (also see Figure 1-14,  4  p.39 for the spectrum of H T P P  ( 2 a ) ) . The spectral pattern observed for H T P P ( C F , ) (46a)  very similar to that of H T P P B r  ( 4 5 a ) . This is reasonable from the view point of the inductive  2  2  4  2  is  2  effect of the B-substituents; the inductive effect of four - B r groups (4a = 0.92)(see Table 1-3, p  p.31) is approximately the same as that of two - C F groups (2a = 1.08). The spectral pattern of 3  p  the P-methylporphyrins (Figure 2-7) shows little change from that of Ff TPP (2a) 2  (Figure 1-14),  indicating that P-methylporphyrins have similar electronic structures to that of 2a. O n the other hand, the patterns of the spectra of P-trifluoromediylporphyrins dramatically change as the number of —CF groups increases (Figure 2-5). In Chapter I, section D . / . b , it was discussed that 3  UV-visible spectra of porphyrins are possibly affected by the electronic and steric effects of substituents on the macrocycle. Takeuchi et al)-^  analyzed each effect on the H O M O s and the  L U M O s of a series of octa p-substituted /^^-tettalds(perfluoromediyl)-porphyrinato Zn(II) (Zn(TPFPPX ), X = H , F, CI, Br, C H ) by semiempirical A M I calculations. In the theoretical 8  3  study, it was found that the H O M O - L U M O (71-71*) gap did not change appreciably if the structure of the macrocycle was kept planar and only X (i.e. electronic effect) is varied. (Zn(TPFPPF ) (12b) 8  was an exception, which showed a significandy larger gap. The rationale for  this is extremely strong electton-withdrawing effect of F according to Takeuchi et al\ 44)  t  although the H O M O and L U M O vary from a Zn(II) porphyrin to another in the series. O n the  101  F i g u r e 2-5. UV-visible spectra of P-ttifluorormemyl-^j-o-tetaphenylporphyrm (a) 46a,  (b) 47a,  and (c) 48a  in CHC1. The narrow lines show ten times magnification 2  2  of the corresponding regions of the thick lines.  F i g u r e 2-6. UV-visible spectra of P-tettabromo-^j-o-tetraphenylporphyrin  (45a)  in CHC1. The narrow line shows ten times magnification of the corresponding 2  2  regions of the thick line.  F i g u r e 2-7. UV-visible spectra of P-memyl-^j-o-tetraphenylporphyrins,(a) 57a, (b) 58a, and (c) 59a in C H C1 . The narrow lines show ten times magnification 2  2  of the corresponding regions of the thick lines.  104  other hand, if the macrocycle distortion was the variable in each Zn(II) porphyrin, significant gap contraction occurred along with macrocycle distortion. Thus, theoretically the pure electronic effect causes littie change and the steric effect (macrocycle distortion) should red-shift absorption maxima in UV-visible spectra. There was no implication that electton-withdrawing effects cause red-shifts in UV-visible spectra. The theoretical study by Takeuchi et al. demonstrated that the red-shifts observed in UV-visible spectra can be attributed mainly to the macrocycle distortion. The estimated gap contraction by macrocycle distortion was a range of 0.1 — 0.2 eV, which corresponds to 24 — 48 nm red-shifts of the lowest energy Q band. 44 1  X  x  Ar  X = H (4b) = Br (8b) = F (12b) = CI (62) = CH (63) 3  H T P P ( C F ) (47a) 2  3  3  around 620 nm for 48a) that of F L T P P (2a)  and H T P P ( C F ) (48a) 2  3  4  show two broad Q bands (also a shoulder at  and the red-shifts of the lowest energy Q band of 47a  and 48a  from the  are 89 nm and 186 nm, respectively. These values are extremely large  compared to 24 - 48 nm obtained for Zn^TPFPPBrg) (8b)  whose macrocycle is  distorted^Ol and thus it is unlikely that the large red-shifts of 47a  and 48a  severely  were caused by  macrocycle distortion only. Furthermore, the red-shift of the lowest energy Q band of H T P P B r (45a) 2  4  for  that of H T P P (2a) 2  is 40 nm but the macrocycle of 45a  is known to be  planar by X-ray crystal structure analysis.202 These results suggest that electton-withdrawing effects of substituents should be involved in order to account for the red-shifts of 45a,  48a.  47a,  and  105  The second unusual feature in the UV-visible spectra of 47 a and 48a  is the order of the  intensity of the Q bands; the Q band at the longer wavelength has a higher intensity which is reversed  in  the  spectra  p-methylporphyrins ( H T P P ( C H ) 2  3  the spectrum of H T P P ( C N ) (34a, 2  H TPP(CF ) 2  3  4  4  2  2a,  of  45a,  H TPP(CF ) 2  3  2  ( 4 6 a ) ,  and  ( 5 7 a ) , H TPP(CH ) ( 5 8 a ) , and H T P P ( C H ) ( 5 9 a ) ) . Only 2  x=4)  2 0 0  3  3  2  3  4  (Table 2-6) mimics those of H T P P ( C F ) (47a) 2  3  and  3  ( 4 8 a ) . In the spectrum of 48a, the Soret band is split into two bands. The split of  the Soret band becomes more prominent in a presumably more electron-deficient porphyrin, H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  (Figure 2-8). A similar spktting of the Soret band observed for  3  48a  and 52a can be observed for H T P P ( C N ) (34a,  x=4) (Table 2-6) as well. The difference between  P-tofluoromedaylporphyrins (47a,  and 34a  2  4  48a  and 52a)  (x=4) is that the Q bands of 34a  are resolved into four unlike the very broad ones observed for 47a,  48a,  or 52a.  (x=4)  The band widths  at the half intensity of the lowest energy Q bands are extremely broad; 94 and 122 nm for those of  47a and 48a compared to 26 nm of H T P P (2a) (Figure 1-14) and 56 nm of H T P P B r ( 4 5 a ) . 2  2  4  The unusually broad Q bands are possibly caused by a hindered rotation of - C F groups that may 3  induce a change of the conformation of substituents (-CF and phenyl groups) and lead to a 3  fluctuation of electronic transitions. The details of the steric interaction and the conformation of -CF  3  and phenyl groups are discussed in section B.4.(3) for the analysis of an X-ray crystal  structure of Zn(TPP(CF ) ) (48b).The unusual Q bands and the split of the Soret band are not 3  4  observed for meso- tettakis(trifluoromethyl)porphyrin (H (CF ) P) (16a 2  3  4  (n=l)) (Figure 1-8, p . l l ) . 39  Other noticeable results for p-perfluoroalkylporphyrins are the low extinction coefficients of the Soret bands (1 - 3 x 10 M'cm" ) compared to the general range for porphyrins!^ 5  1  low extinction coefficient is seen in H (CF ) P (16a, 2  3  4  a n c  j  a  s  irnilar  n=l). Presumably, rotation of - C F groups 3  106  causes a fluctuation o f electronic transitions and leads to the broad absorption w i t h l o w intensities.  300  400  500  600  700  800  900  1000  Wavelength (nm)  F i g u r e 2-8. U V - v i s i b l e spectra o f 52a i n C H C 1 . T h e narrow line shows 2  2  ten times magnification o f the corresponding regions o f the thick line.  107  The unusual spectral pattern, especially in terms of the pattern of the Q bands, of 47a, 4 8 a and  5 2 a  is similar  (bacteriochlorin) (64)  to that  of the UV-visible  spectrum  of P-tetrahyckoporphyrin  (Figure 2-9). Thus, porphyrin 47a, 48a, and 5 2 a may have a similar  electronic structure to that of bacteriochlorin (64), although the Q bands of H T P P ( C F ) ( 4 7 a ) , 2  3  3  H T P P ( C F ) (48a) and H T P P ( C F ) ( C F C F ) (52a) are not as intense and sharp as those of 64. 2  3  4  2  3  3  2  3  As shown in Scheme 2-9(a), bacterichlorin (64)  is only allowed to take one 187T-electron  conjugated pathway (shown by the dotted line in the structure). The unique spectral pattern of 64, for example, compared to that of H T P P (2a)(Figure 1-14, p.39), is due to the distorted 2  electronic pathway.203 The distorted electronic pathway of 6 4 also results in the H O M O L U M O gap contraction and thus leads to the red-shift of the low energy Q band.!42,204,205 \ rationale for the possibly similar electronic pathway of P-trifluoromethylporphyrins to that of 6 4 is that the reduced electron density of the pyrrolic P-C-C bonds where —CF groups reside may 3  be disadvantageous for the conjugated 1871-electron path.  As discussed in Chapter I, section DJ.c, there are two possible tautomers for H T P P (2a) 2  in terms of the 187X-electron pathway or the location of N - H protons (see Figure 1-25, p.59) and the two tautomers  are indistinguishable at room temperature, leading to an averaged  derealization of the two electronic pathways. Unlike the case in 2a, the electronic pathways in P-trifluoromethylporphyrins 47a, 48a, and 5 2 a may be distorted as in bacteriochlorin (64) due to the strong electron-withdrawing substituents on the P-position of the pyrroles in the antipodal positions. These may result in the structure shown in Scheme 2-9(b). In order to assess the electronic pathway of trifluoromethylated porphyrins, H N M R experiments to determine the a  location of N H protons were attempted through which the electronic pathway could be  R = H: H TPP(CF ) 2  3  (47a)  3  R = C F : H TPP(CF ) 3  2  3  4  (48a)  R = C F C F : H T P P ( C F ) ( C F C F ) (52a) 2  3  2  3  3  2  3  (a) 187T-electron pathway of bacteriochlorin (64) and (b) the possible electronic pathway of P-ttifluoromethylporphyrins.  Scheme 2-9.  109  determined. The results of the N M R experiments are shown later (p. 116).  In summary, red-shifts in the UV-visible spectra of the P-tafluoromethylporphyrins are possibly caused by macrocycle distortion as well as electronic effects. As shown in Table 2-6, as the number of the perfluoroalkyl moieties increases (2a  — » 46a  — » 47a  — » 48a  — > 52a),  the  absorption maxima in the spectra progressively shift to longer wavelengths. The observed redshifts were unusually large for the effect of macrocycle distortion alone. The strong electronwithdrawing effect of —CF groups on the pyrrolic P-positions of antipodal pyrroles may be 3  affecting the electronic structure that is probably similar to that of bacteriochlorin and results in the unusual UV-visible spectra of the P-trifluoromethylporphyrins.  (2) Absorbance vs. concentration of 48a According to Ono etal^Z  a  s  discussed in Chapter I, section D.i.b., it seems that electron-  deficient porphyrins have some tendency to aggregate. Since p-trifluoromethylporphyrins are extremely electron-deficient, aggregation of P-trifluoromethylporphyrins might occur. There are also reports that sphtting of the Soret band is occasionally accompanied by porphyrin dimerization.206,207 As shown in Figure 2-5, the Soret bands of H T P P ( C F ) (48a) 2  H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  3  3  split. This may be an indication of aggregation of porphyrins. In  order to examine aggregation of P-trifluoromethylporphyrins, the behavior of Ff TPP(CF ) 2  and H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  3  and  4  3  4  (48a)  in solution was investigated by UV-visible spectroscopy.  Aggregation of porphyrins is often detected in the concentration range, 10" - 10" M.^69 As this 4  concentration range is suitable for UV-visible  spectroscopy,  the spectral changes  concentration for 48a and 52a in C H C 1 and benzene were investigated. 2  2  7  with  110 Figure 2-10  shows the UV-visible spectral change of 48a  in CH C1 and absorbance vs. 2  2  concentration plot over the concentration range 5.90xl0~ to 2.95xl0~ M. 7  4  Perfect linear  correlation between absorbance and concentration at five different wavelengths was obtained with coefficients of correlation close to 1.208  j should be noted that usually absorbance 1.5 is t  the upper limit for analysis of Beer's law. The plot of the data at 620 nm, however, proves the linear relationship of the concentration and the absorbance. Figure 2-11 result obtained for 52a  in CH C1 .  concentration  also  range  2  The same experiments using 48a  2  showed  the  linear  correlation  shows that a similar  in benzene in the similar  between  absorbance  concentration (data not shown). These results show that the structures of 48a  and 52a  and are  retained in solution in a range of concentrations (5.90 x 10~ - 2.95 x 10~ M). Since non-linear 7  4  spectral changes were not detected in this concentration range, it was presumed that P-trifluoromethylporphyrins (48a  and 52a)  are monomelic in solution in the range of the  concentration for the UV-visible spectroscopy.  b. UV-visible spectra of metalloporphyrins Figure 2-12 C o ( T P P ( C F ) ) (48e) 3  that of 48b.  4  shows  the  UV-visible  spectra  3  in CH C1 . For comparison, the spectrum Z n ( T P P ) (2b) 2  4  Although the absorption bands are broad, the Soret bands do not split. As shown in  3  4  were red-shifted and the extinction  were decreased compared to those of Z n ( T P P ) (2b).  O n the other hand, the  positions of absorption maxima and extinction coefficients of Z n ( T P P ( C H ) ) (59b) 3  to those of Z n ( T P P ) (2a).  2b  to  48b.  As  4  are similar  Thus, electronic and structural deviations of the macrocycle in  may be very small from those of Z n ( T P P ) (2a). of  and  is also shown with  2  Table 2-7, the absorption maxima of Zn(TPP(CF ) ) (48b) coefficients  Zn(TPP(CF ) ) (48b)  of  described  in  the  59b  The red-shift of the Q band is 114 nm from that discussion  of  the  UV-visible  spectra  of  Ill  (a)  Concentration X 10 (M) 4  Figure 2-10. (a) UV-visible spectral change of H T P P ( C F ) (48a) over the concentration 2  3  4  range from 5.90 X 10" to 2.95 x 10" M in C H C 1 at room temperature. 7  4  2  (b) Absorbance vs. concentration plot at 444 (O),  2  463 (•), 580 (•) , 620 (•) and 832 nm  (A).  112  Concentration X 10 (M) 4  Figure 2-11. (a) UV-visible spectral change of H T P P ( C F ) 3 ( C F C F ) (52a) over the 2  3  2  3  concentration range from 9.87 X 10" to 2.47 x 10" M in C H C 1 at room temperature. 7  4  2  (b) Absorbance vs. concentration plot at 444 (O),  2  468 (•), 586 (•) , 628 (•) and 844 nm  (A).  113  Figure 2-12. UV-visible spectra (thick lines) of Zn(TPP(CF ) ) (48b) and CoCrPP(CF ) ) (48e) in CH C1 . The narrow line is Zn(TPP) (2b). 3 4  3 4  2  2  114  P-trifluoromethyl porphyrin free-bases, red-shifts caused by a large macrocycle distortion is at best 24 — 48 nm according to calculations by Takeuchi et al}^ the Q band in 48b  Therefore, the large red-shift of  must be attributed to both the steric and electronic effects.  T a b l e 2-1. UV-visible absorption maxima of metalloporphyrins. A,max (nm)(log s)  Porphyrin Zn(TPP) (2b) Zn(TPP(CF ) ) (48b) Zn(TPP(CH ) ) (62b) Co(TPP(CF ) ) (48e) Fe(TPPBr )Cl (45e) Fe(TPP(CF ) )Cl (48f) Fe(TPP(CF ) (CF CF ))Cl (52c) (FeTPP(CF ) ) Q (61) ( )* : relative intensity 3  4  3  3  4  4  4  A  rationale  Co(TPP(CF ) ) (48e) 3  4  3  4  3  3  3  4  2  3  2  for  explaining  why  419 442 420 440 433 452 459 435  the  (5.83), 548 (4.36), 582 (3.41) (5.37), 662 (4.31) (5.63), 551 (4.26), 584sh(3.66) (5.06), 636 (4.32) (5.02), 520 (4.11), 591 (3.81), 700 (3.56) (4.76), 618 (4.12) (4.62), 624 (4.00) (1.00)* 700 (0.27)*  Soret  bands  of  Zn(TPP(CF ) ) (48b) 3  4  and  do not split is that the postulated distorted electronic pathway (Scheme 2-9)  may be disturbed by metallation. However, the macrocycles seem be forced to take an unusual electronic structure even in the presence of a central metal. For instance the Soret band of 48b  is  not completely symmetric, indicating an overlap of two bands, and the pattern of the Q bands are significandy different from that of Zn(TPP)  Figure 2-13 Fe(TPPBr )Cl 4  shows  the  UV-visible  (2b).  spectra  of  hemins (Fe(III)Cl  complex)  ( 4 5 e ) , Fe(TPP(CF ) )Cl ( 4 8 f ) , and FeCTPP(CF ) (CF CF ))Cl ( 5 2 c ) . The absorption 3  4  3  3  2  3  maxima and extinction coefficients are also listed in Table 2-7. The Soret bands of 48f red-shift from that of 45e  and 52c  and the intensities of the absorption bands progressively decrease as  the number of perfluoroalkyl moieties increases. The p,-oxodimer Fe(III) complex (61)  showed  very broad UV-visible bands and a low ratio of intensity of the Soret to the Q band (Soret/Q  45e  48f  52c  12  300  400  500  600  700  800  900  1000  Wavelength (nm)  F i g u r e 2-13.  UV-visible spectra of [FeTPP(CF ) ]Cl ( 4 8 f ) ( — ) , 3  4  [FeTPP(CF )3(CF CF )]Cl ( 5 2 c ) ( — ) , [FeTPPBr ]Cl ( 4 5 e ) ( —) in C H C 1 . 3  2  3  4  2  2  116  band intensities = 3.7) compared to Soret/Q band intensities = 6.6 of the u,-oxo dimer Fe(III) complex of 45 ( ( F e T P P B r ) 0 ) . 4  192  2  In summary, the UV-visible spectra of metalloporphyrins of 48 and 52 show red-shifted and very broad absorption bands with decreased extinction coefficients compared to those of metalloporphyrins of H T P P (2a), 2  H TPPBr ( 4 5 a ) , and H T P P ( C H ) ( 5 9 a ) . This is a pattern 2  4  2  3  4  similar to that observed for the corresponding free-base species. The presence of the electronwithdrawing and steric effect of trifluoromethyl groups (see Chapter II, section B.4.b.(3) for the discussion of the sizes of —CF and — C H groups) may lead to the characteritic UV-visible 3  3  absorption bands of these novel P-tiifluoromethylmetaUoporphyrins.  2. NMR spectroscopy As discussed in Chapter I, section D . i . c , electronic effects of a P-substituent on the porphyrin macrocycle can affect the 1871-electron pathway, or the location of N H protons of the porphyrin macrocycle, while very unusual UV-visible spectra of P-trifluoromethylporphyrins were obtained. EspeciaUy, the UV-visible spectra of H T P P ( C F ) ( 4 7 a ) , H TPP(CF ) ( 4 8 a ) , and 2  H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  3  3  3  2  showed a similarity to that of bacteriochlorin (64),  3  4  indicating these  P-trifluoromethylporphyrins have a similar electronic structure to that of 64. The major purpose of this section is to determine the electronic structure of p-trifluoromethylporphyrins by N M R spectroscopy. The analysis of the positions of N - H protons was achieved by inference through ' H C O S Y or H homonuclear decoupling experiments. The second part of this section l  describes an unusual chemical shift of P-pyrrolic protons of p-tetrakis(trifluoromethyl)-mesotetraphenylporphyrin ( 4 8 a ) .  117  a. Determination of electronic pathway of B-trifluoromethylporphyrins. As shown in Figure 1-25, the N - H tautomerism accompanies the tautomerism of the 187Telectron pathways of the macrocycle. Tautomerism is generally fast on the N M R time scale at room temperature and we cannot assign the N - H protons on specific pyrroles.  166  However,  when the temperature is lowered the tautomerism is slowed. For example, the H N M R showed :  two resolved lines for the two kinds of pyrrolic P-protons ( H H T P P (2a) 2  and H  A  in Figure 1-25) of  B  below 220 K.174 Electronic effects of substituents on the macrocycle are also  known to affect the tautomerism of a macrocycle (see Chapter I, section D.J?.C). According to a low temperature N M R study,  187t-electton pathway of the porphyrin tends to avoid a  1  pyrrolic Cp-Cp bond where an electron-withdrawing substituent resides because of the reduced electron density. It may be worth mentioning the *H N M R of H T P P B r (45a) 2  4  reported by  Crossley etal.^^ in which a long-range coupling between N - H and pyrrolic p - H was observed. Figure 2-14 shows the ' H N M R spectra of 45a  obtained by the author. The doublet of pyrrolic  P - H with a coupling constant of 1.4 H z is due to the long-range coupling between N - H and pyrrolic P - H which is decoupled by irradiation at N - H (the doublet of P - H can be observed by a 200MHz spectrophotometer as well).  Long range H-H couplings (i.e. over four or more bonds) are sometimes observed in a planar zig-zag orientation (the structure is shown below) and an approximate representation of theoretical calculations for a / i . 4  H  ^C^  H  H 2  coupling in unstrained systems is given by (2.1):  o  C  1  = cos (j) + cos (|) -0.7 2  H 2  2  1  2  (2.1)  hr  where (j^ and <)> are the H - C ' - C ^ - C 2  % .  3  and C - C - C - H 1  2  3  2  dihedral angles in the coupling  1  ;  1  1  j  1  1  1  8.6  1  1  1  1  1  1  8.4  1  1  1  1  1  8.2  1  1  1  1  j  1  8.0  1  1  1  r  7.8  Chemical shift (ppm) (b)  I  Chemical shift (ppm)  F i g u r e 2-14.  4 0 0 M H z *H nmr spectra of H TPPBr (45a) 2  (a) Normal spectrum.J(NH-pH)=1.4 Hz. 4  4  in C D C 1 at room temperature,  (b) Decoupled at -NH  3  (-2.88ppm).  119  H  cx 4  aromatics  cyclohexanes  meta  equatorial-equatorial  /=2-3Hz  4  /=l-2Hz  pathways.209 The examples of such long-range couplings are shown b e l o w . ^ The commonest 2  example of a long-range coupling is the meta J coupling of 2 — 3 H z in aromatics. Long-range 4  couplings are also observed in saturated systems such as the equatorial-equatorial coupling (1 — 2 Hz) in cyclohexanes and even a / coupling can be observed for H and H in quinoline. 5  4  8  Pyrroles are planar aromatic systems and have such zig-zag orientations between N - H and P-H and thus observing a J coupling of ~1 H z between N - H and p - H coupling is reasonable. In 4  porphyrin 45a  the N - H - P - H coupling can be observed at room temperature (see ' H N M R  spectrum of H T P P (2a)  at room temperature (Figure 1-23) for comparison). Thus, the N - H  2  localization tells us that the macrocycle has a specific 187t-electron pathway as shown in Figure 2-14.  Using H T P P ( C F ) 2  3  3  ( 4 7 a ) , which resulted in a bacteriochlorin-type UV-visible spectrum,  determination of the positions of N - H protons was attempted. Figure 2-15 shows the 400 M H z H N M R spectrum of 47a.  l  47a  The reason porphyrin 47a was used was that H (see the structure of 5  in Figure 2-15) could be a good probe to determine the electronic pathway for the analysis  of correlation between pyrrolic P - H and N - H protons. The spectrum shows the N - H protons (two broad singlets at -1.73 and -1.86 ppm), meta+para-phenyl-H  (7.66 - 7.81 ppm), ortho-  phenyl-H (8.11 - 8.24 ppm), and pyrrolic P - H (8.30 - 8.77 ppm). It is easy to assign H  5  it  appeared  appeared as  a singlet  and other  pyrrolic  P-Hs  (H , H , H , and H ) 1  2  3  4  because  CHCL  (a)  H  5  Ph  H  1  47a  U  i  10  r  _  6  9  r  i  5  4  i  i  3  "i -1  r  2  1  0  r  Chemical shift (ppm) (b)  »./>-phenyl-H(12H)  I  I  9.0  8.8  I  8.6  I  8.4  1  1  8.2  8.0  I  7.8  1  » — i  7.6  -1.7  1  1  -1.9  Chemical shift (ppm)  F i g u r e 2-15. 400 M H z H N M R spectra of H T P P ( C F ) (47a) in C D C 1 J  2  3  3  at room temperature.(a) Full spectrum and (b) expansion of the peaks. Peaks labeled with * are impurities.  3  121  F i g u r e 2-16. 400 M H z C O S Y spectra of H T P P ( C F ) ( 4 7 a ) . (a) Full spectrum 2  and (b) expansion of one of the circled areas.  3  3  122  as doublets due to coupling to adjacent protons; H - H  2  and H - H * . Assignment of each of H , 3  H , H and H was not attempted, since it was unnecessary for determination of the electronic 2  3  4  pathway. Unlike the case of H T P P B r 2  ( 4 5 a ) , the 400 M H z H N M R of H T P P ( C F ) (47a) did ]  4  2  3  3  not show the fine splitting of pyrrolic (5-H signals. However, the coupling connectivity between pyrrolic P - H and the N - H protons was observed by a C O S Y experiment at room temperature, as indicated by the dotted circles in Figure 2-16(a). Expansion of the correlation (Figure 2-16(b)) clearly showed that the N - H protons are not coupled to H but to H , H , H , and H . By the 5  2  3  4  experiment it can be concluded that locations of the N - H protons are assigned on the pyrroles not substituted by —CF groups and thus at room temperature the porphyrin preferably takes the 3  electronic structure shown in the box in Figure 2-17.  Ph C F  iW  V-NH Ph-  During the course of the N M R  3  CF  3  -Ph  F C3  H  Ph  H  Ph  F i g u r e 2-17. 187t-electeon pathway of H T P P ( C F ) ( 4 7 a ) . 2  3  3  experiments, it was also discovered that N - H protons of H T P P ( C F ) (47a) 2  3  3  can exchange easily  with residual water. The observation is shown in Figure 2-18(a) and (b). In the presence of trace water (Figure 2-18(a)), the signals from water and N - H protons are broad. In the absence of water (Figure 2-18(b)), on the other hand, the spectra showed two N - H proton signals clearly. In addition to this observation, intensities of H , H , H , and H signals dropped significantly and 1  2  3  4  peak widths were obviously greater compared to those observed in Figure 2-18(a). In contrast, such  significant  changes  were  not  observed  for  H  5  and  o-phenyl-H signals.  The  123  CHCL  (a) H  5  8.60  8 .40  8.00  8 .20  H 0  i I i i ii  -  5  m  N H  2  """I' r i "i—i—i—i—[—i—[—rI—[—i—i—r~r  (PP )  4  3  2  1  Chemical shift (ppm)  (b)  o-phenyl-H H  5  H ^ H ^ H  4  ^  r  30  8.60  8.40  8.20  8.00  (PP ) m  NH inwtHimiii*iiimin*i  I ' I 8 7 11  1  ».i>mw>i< s*—  niiirtiiMil  II>II|IHI#IH  iimUwi>i'i  2  1  UNI  i'mfim n  1  Df'tlt«  n^ ' i ' ' i -1 -2 -3 -1-  4  3  0  1  1  Chemical shift (ppm)  F i g u r e 2-18. 200 MHz H NMR spectra of HTPP(CF) (47a) !  2  33  (a) in the presence of  and (b) in the absence of residual water in CDC1 . Inner traces are expansion of the 3  region of pyrrolic P - H and or^o-phenyl-H. Designation for pyrrolic P-Hs was given in Figure 2-15.  124  change  from  Figure 2-18 (a)  H T P P ( C F ) (47a) 2  3  The  to  (b)  evidently  confirms  the  electronic  pathway  of  protons  in  seems not as strong as that of  47a.  as shown in Figure 2-17.  3  coupling  connectivity  between  the  P-tettakis(trifluoromemyl)porphyrin H T P P ( C F ) (48a) 2  3  4  N-H  and  the  P-H  Unlike the P-H signal of H T P P B r (45a)(doublet, see Figure 2-14), the P-H signal of 48a was a 2  4  sharp singlet and the coupling connectivity could not be observed by a C O S Y experiment either. However, there was a slight increase of the absolute intensity of P-H upon irradiation at N-H (-1.42 ppm) and the intensity of o-phenyl-H and w+/)-phenyl-H signals was unchanged. Although a clear evidence for the connectivity between N-H and P-H protons for 48a  was not  obtained, this is also a phenomenon expected from the porphyrin having an electronic structure as shown in Figure 2-17 deft). A coupling through bonds is transmitted via the bonding electrons.209 Accordingly, it should be harder to transmit the coupling if the density of bonding electrons is lowered. Although the orientation of the N-H and P-H in the pyrroles may satisfy the criterion for a long-range coupling (planar zig-zag orientation), a possible reason for not observing a spurting of the P-H signals due to long-range couplings between the N-Hr and P-Hr may be the lower electron density of the macrocycle induced by the strong electton-withdrawing effect of the —CF groups. 3  Analysis of the electronic pathway of P-ttimethylporphyrin H T P P ( C H ) (58a) 2  3  3  was also  attempted. However, any information that suggests the porphyrin takes a specific electronic pathway could not be obtained. As shown in Figure 2-19, the N-H signals are quite broad even in the absence of water, indicating N - H tautomerization at room temperature.  125  10  9  8  7  6  5  4  3  2  1  0  -1  -2  -3  Chemical shift (ppm)  0) •CH O ~ 3 P (6H) (3H) C  3  • =  «?+/)-phenyl-H(12H)  H',H ,H ,H 2  3  4  o-phenyl-H(8H)  8.6  8.4  8.2  8.0  T—r-ft 1 1 i 1 . 1 1 . 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 .  7.8  7.6  3.0 2.8 2.6 2.4 2.2  Chemical shift (ppm)  F i g u r e 2-19. 400 M H z H N M R spectra of H T P P ( C H ) (58a) l  2  3  3  in C D C 1  3  at room temperature, (a) Full spectrum, (b) Expansion of the selected peaks. Peaks labeled with * are impurities.  2.0  126  These  observations  for  P-trifluoromethyl  and  P-methylporphyrins  by  NMR  spectroscopy suggested that in order to observe the coupling connectivity between the N - H and the P~H, a porphyrin may have to satisfy at least the following conditions: (1) the porphyrin has substituents  on the antipodal pyrroles and (2) the substituents are moderately electron-  withdrawing. The ' H N M R experiments showed that at room temperature the 187T—electronic pathways for P-tris- and P-tettaltis(teifluoromethyl)porphyrins (47a  and 48a)  are fixed so that  they avoid the paths where —CF groups reside because of the reduced electron density. This 3  result is similar to those obtained for p-mono-substituted wwo-tetraphenylporphyrins ^ 17  (Chapter I, section D.3.) but it has to be emphasized that one of the N - H tautomers can be locked at room temperature presumably due to the strong electron-withdrawing effects of —CF groups. O n the other hand,  H N M R spectra of P-tjimethylporphyrin H T P P ( C H )  a  2  3  3  3  (58a)  suggested that tautomerization of the N - H protons or the electronic pathways occur as is the case of H T P P (2a).  The results obtained by the N M R studies for P-trifluoromethyl- and  2  p-metliyl-porphyrins agree with the prediction made by the UV-visible spectra of these porphyrins in terms of the electronic structures.  b. Unusual 'H NMR chemical shiftfor pyrrolic ^-protons ofH TPP(CF ) 2  3 4  The chemical shift for the pyrrolic p - H of H T P P ( C F ) (48a) 2  3  4  (48a)  appears at fairly high field  compared to those of other wwo-tetraphenylporphyrin derivatives such as H T P P B r (45a) 2  4  or  H TPP(CH ) ( 5 9 a ) . This part of the N M R section is a discussion of the possible origin of this 2  3  4  unique chemical shift for the pyrrolic P-protons of H T P P ( C F ) ( 4 8 a ) . Figure 2-20 shows the 2  200 M H z  'HNMR  H T P P (2a)  of  2  3  and P-tetrasubstituted-^j-o-tetraphenylporphyrins  H TPPBr ( 4 5 a ) , H TPP(CF ) ( 4 8 a ) , and H T P P ( C H ) (59a) 2  4  2  3  4  4  2  3  4  in Q D . The porphyrin 48a is the 6  B-H N H chem. shift (ppm)  m,p-phenyl-H  (a) o-phenyl-H  9 . 0  8 . 8  8 . 8  8 . 4  8 . 2  -2.13  8 . 0  7.6  7 . 8  7.4  7.2  m,p-ph.eny\-H (b)  o-phenyl-H  B-H  9 . 0  8 . 8  8 . 6  8 . 4  8 . 2  8 . 0  -2.69  7 . 8  7 . 6  p-H  7 . 4  7 . 2  /»,/>-phenyl-H  <?-phenyl-H  (c)  -1.42  ' ,1 Mir**-*? J.O  8 . 8  8 . 6  8 . 4  8 . 2  8 . 0  7 . 8  7 . 6  7 . 4  7 . 2  «,/>-phenyl-H  (d)  o-phenyl-H  9 . 0  8 . 8  8 . 6  8 . 4  8 . 2  8 . 0  -2.72  7 . 8  7 . 6  7 . 4  7 . 2  C h e m i c a l Shift (ppm)  F i g u r e 2-20.200 M H z H N M R spectra o f (a) H T P P (2a), l  2  (c) H T P P ( C F ) (48a) 2  * is  1 3  3  4  and (d) H T P P ( C H )  C satellite o f benzene.  2  3  4  (59a)  (b) H T P P B r ( 4 5 a ) , 2  4  i n C D a t r o o m temperature 6  6  128  most soluble in benzene but unfortunately is sparingly soluble in CHC1 in neutral conditions. 3  Accordingly, the comparison of the N M R spectra was performed in C D . (Porphyrin 48a is also 6  6  very soluble in T F A and the N M R spectra of related porphyrins in T F A - d will be shown later in this section.) The concentrations of porphyrin 45a, H T P P ( C F ) ( 4 8 a ) , and Ff TPP(CH ) 2  were  set  to  H T P P (2a) 2  0.0025 - 0.003 M  3  4  2  3  4  (~ 1 mg porphyrin/0.5 m L QDg). The concentration  (59a) of  was 0.0065 M . Porphyrin 48a is very different from other porphyrins in terms of the  chemical shift of pyrrolic (3-protons and N - H protons. A l l the porphyrins (2a, 45a,  48a,  and  59a)  have phenyl groups on the wwo-positions of the macrocycle and the chemical shifts for phenyl protons appear at similar chemical shifts. This indicates that the environment of phenyl substituents is independent of the macrocycle structures, although there might be some interactions between P-substituents and ort/w-phenyl-Hs. Two possibilities were considered for the unusual chemical shift of pyrrolic P-proton signal of 48a.  The first possibility is a  deterioration of ring current due to a macrocycle distortion and strong electron-witiidrawing effect. The P-pyrrolic protons are deshielded and the N H protons are shielded due to the ring current effect of the macrocycle (Chapter I, section DJ.a.  for the ring current and chemical  shifts). The —CF group is a strongly election-withdrawing and bulky substituent. Accordingly, 3  the macrocycle in 48a  is expected  be electron-deficient  and distorted (see  Chapter II,  section B.4.b.(3) for steric interaction between substituents and a macrocycle distortion of Zn(TPP(CF ) ) ( 4 8 a ) ) . Consequendy, the smooth ring current is possibly hampered by the 3  4  electronic and the steric effects of the - C F groups and deshielding and shielding effects will be 3  weakened. Appearances of the pyrrolic P-proton signal at the higher field (ca. 0.9 ppm shift from that of H T P P (2a) 2  and of the N H proton signal at the lower field (ca. 0.6 ppm shift from that  of 2a) are explained by this hypothesis.  129  The  second possibility is an aggregation. As shown by O n o et alX^^  (Chapter I,  section D.i.b.), P-pyrrolic protons shift to the higher field when the porphyrins aggregate. Aggregation of porphyrin 48a  and H T P P ( C F ) 3 ( C F C F ) (52a) 3  2  2  3  has already been investigated  using UV-visible spectroscopy for a concentration range of K T - 1 ( T M and the monomer 7  4  form of the porphyrins was suggested. Since the concentration of 48a for the N M R spectrum shown in Figure 2-20 was much higher than those examined in the UV-visible spectroscopy, the possibility of aggregation was investigated. A t 0.00045 M , 0.001 M , and 0.002 M (0.9 mg/0.5 m L was the maximum concentration) the chemical shift of p-pyrrolic protons of 48a appeared always at 8.00 ppm. It should be noted that 0.00045 M is nearly equal to the maximum of the concentration range investigated by the UV-visible spectroscopy. This means the structure of porphyrin 48a is unchanged and presumably exists as monomers in the concentration of I O — -7  2 x 10 M in benzene. Thus, the large highfield chemical shift of pyrrolic P-protons and 3  lowfield chemical shift of N H protons of H T P P ( C F ) (48a) 2  3  4  are probably due to a macrocycle  distortion. In fact, a large downfield shift of N H (that appears at -0.5 ppm) of P-octabromo^jo-tetrakis(perfluorophenyl)porphyrin (I^TPFPPBrg)(8a)(Figure 1-8, p.11) (-2.76 ppm) of HTPP(2a), was explained by a severe macrocycle distortion of 2  from  that  8a.^6  The unusual chemical shift of pyrrolic P-protons of 48a was also observed in deuterated ttifluoroacetic acid (TFA-d). Comparison of the ' H N M R spectrum of 48a with H T P P B r 2  and H T P P ( C H ) (59a) 2  3  4  4  (45a)  is shown in Figure 2-21.* Figure 2-21 (a) shows the spectrum of 48a in  T F A - d . The assignment of the signals was done by comparing the peak integrations. The pyrrolic  UV-visible spectra o f diacids o f 48a and 59a are shown i n appendix B (P.233).  130  B-H(4H) /»,/)-phenyl-H(12H)  1  i—i  •  9.40  •  |  i—i  I—•  9.20  |  .  9.00  I  I  i  1  8.80  1  . 1 1 • 1 1 1 1 . |—i 1 1 1 8.60 8.40 8.20  1  ,,,1  ,—r-  8.00  Chemical shift (ppm)  F i g u r e 2-21. 400 M H z *H N M R spectra of diacid of (a) H T P P ( C F ) ( 4 8 a ) , 2  (b) H T P P B r (45a) 2  4  and (c) H T P P ( C H ) (59a) 2  3  4  3  4  in T F A - d at room temperature.  131  P - H for 48a  appeared at 8.28 ppm as a sharp singlet and the chemical shift was about 0.5 ppm  higher than those for pyrrolic P - H of 45a  (Figure 2-21 (b)) and 59a  (Figure 2-21 (c)), indicating  that there are macrocycle distortions and electron-withdrawing effects of - C F groups in 48a.  An  interesting observation in the N M R spectra of these porphyrins in T F A - d is that porphyrin  45a  and 59a  48a  3  showed splitting of the o-phenyl-H signal into two peaks with equal area but  showed only one peak for c-phenyl-H. It is known that protonation of the macrocycle of ^jo-tetraarylporphyrins causes severe macrocycle distortion into a saddle shape and the distortion accompanies rotation of the meso-atyl groups along the C - C axis between the porphyrin macrocycle and the aryl groups.^ -0,211 Modes of distortion of the macrocycle upon 1  protonation are shown HyperChem.188 T  nm  e  in Figure 2-22.  diacid form of D  The structures  4 h  in the figure were  porphyrins such as Ff TPP (2a),  created by  all o-phenyl-Hs are  2  equivalent (Figure 2-22(a)), which has been observed by X-ray crystal crystallography^l 0,211 !  anc  j  H N M R in TFA-d.212 Since the pyrrole rings are alternately tilted up and down to the average  plane of the macrocycle, in the H TPP(CH ) 2  3  4  case of D  2 h  porphyrins such as H T P P B r (45a) 2  4  or  ( 5 9 a ) , a distorted porphyrin macrocycle should have two different faces regarding  the average plane of the macrocycle (Figure 2-22 (b)) and it is reasonable for D  2 h  porphyrins to  have two kinds of non-equivalent o-phenyl-Hs and to show two peaks in the N M R spectra. However, this analysis does not fit to the N M R spectrum of H T P P ( C F ) (48a) 2  3  4  in T F A - d which  shows only one broad singlet for o-phenyl-Hs. A rationale for this observation may be rotation of - C F 1 9  3  groups. One piece of information regarding rotation of - C F  F N M R spectrum of H T P P ( C F ) (48a) 2  3  4  3  groups is that the  shows a sharp singlet at room temperature. The steric  interaction between the meso-phenyl groups and - C F groups on the pyrrolic P-positions was 3  found to be significant (see Chapter II, section B.4.b.(3)). Thus, rotation of - C F  3  possibly  132  F i g u r e 2-22. Structures of (a) [ H T P P ] and (b) [ H T P P ( C H ) ] . 2+  4  2+  2  Molecular structures were created by HyperChem geometry optimization ( M M + ) .  189  3  4  133  induces rotation of meso-phenyl groups along the C - C axis between the macrocycle and the phenyl groups. As a result of the continuous conformation change, o-phenyl-Hs may lose nonequivalency and show one peak in the N M R spectrum in spite of the mode of distortion in the D  a  porphyrin upon protonation. Unlike the cases of the free-base and diacid form of H T P P ( C F ) 2  spectrum of Zn(TPP(CF ) ) (48b) 3  4  3  4  ( 4 8 a ) , the N M R  in CDC1 at room temperature showed a pyrrolic p-H signal 3  shifted the most downfield (8.43 ppm) compared to other two chemical shifts of o-phenyl-H at 8.07 ppm and ^ - p h e n y l - H at 7.76 ppm (Table 2-8). The electron-deficiency of 48a  may be  relaxed by metallation with Zn(II) and the ring current may be increased. O n the other hand, other Zn(II) porphyrins in the table did not show significant change in chemical shift of the pyrrolic P-H from those of corresponding free-base porphyrins.  T a b l e 2-8. Chemical shift values of zinc P-tetrasubstituted /^o-tettaphenylporphyrins ' H (ppm)  porphyrin 3  H TPP(CF ) 2  3  P-H (48b)  Zn(TPP(CF ) ) 4  (48a)  4  (59b)  Zn(TPP(CH ) ) 3  H TPP(CH ) 2  3  4  (59a)  4  Zn(TPPBr ) (45b) H TPPBr (45a) 4  2  4  (2b)  Zn(TPP) H TPP 2  o-phenyl-H  8.43 (s, 4H)  8.07 (m, 8H)  7.70 (m, 12H)  CDC1  8.00 (s, 4H)  8.11 (m, 8H)  7.45 (m, 12H)  QD  8.65 (s, 4H)  8.06 (m, 8H)  7.75 (m, 12H)  CD C1  8.44 (s, 4H) 8.61 (s, 4H) 8.68 (d, 4H)  8.07 (m, 8H) 8.02 (m, 8H) 8.18 (m, 8H)  7.71 (m, 12H) 7.80 (m, 12H) 7.78 (m, 12H)  CDC1 DMSO-d CDC1  8.90 (s, 4H)  8.08 (m, 8H) 8.22 (m, 8H)  7.73 (m, 12H)  CDC1  3  7.75 (m, 12H)  CDC1  3  8.86 (s, 4H)  (2a)  solvent  #?,/>-phenyl-H  In summary, H N M R experiments using H T P P ( C F ) (47a) ]  2  3  3  3  6  2  2  3  6  3  and H T P P ( C F ) 2  3  4  (48a)  showed that the positions of the N - H protons were locked at room temperature due to —CF groups  on  the  antipodal  pyrroles.  The  positions  of  the  N-H  protons  in  3  the  P-Oifluoromethylporphyrins indicate that the 187t-electronic pathway of the macrocycle avoids positions where —CF groups reside. Positions of the N - H protons in P-trimethylporphyrin 3  H T P P ( C H ) (58a) 2  3  3  were  not resolved by the N M R experiment  at room temperature,  134  presumably due to exchange of the two possible N - H tautomers. Thus, for a locked N - H tautomer or 187t-electton pathway, strong electxon-withdrawing effects by substituents will be required. The analysis by the N M R experiments concerning the electronic structure of the macrocycle agrees with the prediction deduced from the UV-visible spectroscopic data that P-trifluoromethylporphyrins may have a fixed  187t-electron  pathway similar to that of  bacteriochlorin.  The  unusual chemical shift  of  the  pyrrolic  P-proton  signal is  characteristic of  H T P P ( C F ) (48a) and is possibly caused by the electton-withdrawing and steric effects of —CF 2  3  4  3  groups.  3. Redox potentials As discussed in Chapter I section D . Z b , electron-withdrawing substituents positively shift the reduction and the oxidation potentials of the porphyrin macrocycle and thus comparison of the redox potentials enables us to estimate the electron-deficiency of porphyrins. So far, we have seen the dramatically different characteristics of P-t^fluoromethyl-^Jo-tettaphenylporphyrins from  those  of  wwo-tettaphenylporphyrin,  p-tettabromo-^ro-tettaphenylporphyrin,  and  P-methyl-^j-o-tetraphenylporphyrins in their UV-visible and N M R spectra. The effects of the strongly electton-withdrawing - C F groups were analyzed qualitatively by those methods. This 3  section describes direct quantitative analysis and comparison of electronic properties of P-trifluoromethylporphyrins  with  those  of  other  related  porphyrin  systems  such  as  Wcvo-tetraphenylporphyrn or p-methylporphyrins based on their results obtained from cyclic voltammetry.  The  purpose  of  this  section  is  to  estimate  electron-deficiency  of  P-trifluoromethylporphyrins and to show some supporting evidence that agrees with those  135  analyses in the previous sections regarding the 187t-electron pathway of the porphyrins. This section is separated into three parts. The first part describes comparison of the ring redox potentials  of  P-tofluoromemylporphyrins  free-base  with  those  of  other  ^j"o-tetraphenylporphyrin derivatives and how the redox potentials changes as the number of — CF  3  group increases. The second part focuses on comparison of the redox potentials of  P-tettasubstimted-^j'O-tettaphenylporphyrinato Zn(II) complexes in order to investigate the electronic effects of substituents on the porphyrins with the same symmetry, D , as that of 2 h  Zn(rPP(CF ) ) (48b) 3  4  (Scheme 2-7).  In  this  comparison,  the  redox  potential  of  p-tettakis(tofluoromemyl)porphyrinato Zn(II) is investigated with other Zn(II) complexes of selected electron-deficient porphyrins. In the first and second parts, the electronic structure of p-teifluoromethylporphyrins  is discussed by comparing the  macrocycles  of  with  those  ^jo-tetraphenylporphyrins.  HOMO-LUMO As  discussed  in  gap of  the  Chapter I,  section D.Za.(2), the first oxidation and reduction of a porphyrin ring correspond to the formation of a 7t-cation radical and a 7t-anion radical.149,150 Strictly speaking, the difference between the potentials to form Tt-cation and 71-anion radicals is not exacdy the H O M O - L U M O gap, but the theoretical H O M O - L U M O gap agrees with the difference between the first oxidation and the reduction potentials. 149,150 j cytochrome P-450 models,  n  m  e final section, the redox potentials of the  P-trifluoromethylporphyrinato Fe(III)  chloride complexes  are  compared with those of Fe(III) complexes of other electron-deficient porphyrins to assess their electron-deficiency and possibility as oxidation catalysts.  136  a. Free-base P-trifluoromethyl-meso-tetraphenylporphyrins Redox potentials of free-base porphyrins were measured under the same conditions; in C H C 1 and with supporting electrolyte, tetrabutylammonium hexafluorophosphate (TBAPFg). 2  2  The  standard potentials  were  obtained  by  the  use  of  an  internal  reference;  ferrocene/ferrocenium couple.213 The experimental details are described in Chpater III.  Cyclic voltammograms of H T P P ( C F ) (46a) 2  Figure 2-23. Porphyrin 46a  3  and H T P P ( C F ) (47a)  2  2  3  are shown in  3  showed the two reduction reactions and two oxidation reactions, but  the two reduction processes were not resolved well and the second oxidation process was not a one-electron process. Porphyrin 47a  showed two well-resolved, one-electron reduction and  one-electron  Figure 2-24  oxidation  H T P P ( C F ) (48a) 2  3  reactions.  shows  the  cyclic  voltammograms  of  at various scan rates. A t any scan rate two clean reversible one-electron  4  oxidations were observed. The reduction processes differed in that the one-electron process was always  irreversible  for  H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  3  the  first  electron.  The  was similar to that of 48a.  electrochemical  behavior  of  The reason for the irreversible reduction  process is not known. The electrochemical reduction may result in a similar change of the macrocycle ring to that observed in the chemical reductions. Such a change led to decomposition of porphyrin 48a and 52a (see Chapter II, section A.l.c.(2), and section A.3.b.).  For comparison, the cyclic voltammograms of (3-methylporphyrins ( H T P P ( C H ) 2  H TPP(CH ) 2  3  3  ( 5 8 a ) , H T P P ( C H ) (59a) 2  3  4  are  shown  in  Figure 2-25.  P-methylporphyrins showed two one-electron reduction and two processes. In addition, porphyrin 58a  and 59a  3  The  2  ( 5 7 a ) , three  one-electron oxidation  showed a third one-electron oxidation process  F i g u r e 2-23. Cyclic voltammograms of (a) H T P P ( C F ) (46a) and (b) H T P P ( C F ) ( 4 7 a ) . Solvent: C H C 1 , [porphyrin]^ 1 x 10 " M , 2  3  2  3  2  3  3  2  2  Supporting electrolyte: [TBAPF ] = 1 x 10 M , Scan rate: 0.05 V / s . White 1  6  arrows indicate ferrocene/ferrocenium coupling; 0.46 V vs. S C E .  138  2.0  1.0  0.0  -1.0  -2.0  Potential (V vs. SCE)  F i g u r e 2-24. Cyclic voltammograms of H T P P ( C F ) (48a) at different scan rates. 2  3  4  Solvent: C H C 1 , [porphyrin]=5 x I O , Supporting electrolyte: [TBAPF ] = 1 x 10 M . 4  2  2  1  6  (a)  X 10 p A  2.0  1.0  0.0  -1.0  -2.0  Potential (V vs. SCE)  F i g u r e 2-25.  Cyclic voltammograms of (a) H T P P ( C H ) 2  (b) H T P P ( C H ) 2  3  3  3  2  ( 5 7 a ) ,  ( 5 8 a ) , and (c) H T P P ( C H ) ( 5 9 a ) . Solvent: C H C 1 ,  [porphyrin]=1 x 10  2  3  3  4  2  M , Supporting electrolyte: [TBAPF ]=1 x 10 6  Scan rate: 0.05 V / s . White arrows indicate ferrocene/ferrocinium coupling: 0.46 V vs. S C E .  _ 1  M.  2  140  that was not observed for H T P P (2a) (see Figure 1-17, p.45). Since the methyl substituents are 2  electron-releasing, the macrocycles are more electron-rich and easier to oxidize. Such a rationale explains the increased difficulty in their reductions. The redox potentials of (3-trifluoromethyland (3-methylporphyrins together with those of H T P P (2a)  and H T P P ( C N ) (32a,  2  2  are summarized in Table 2-9. The redox potentials of H T P P (2a)  161  by this work show good  2  agreement with the reported literature values. '  x = 2-4)  X  Thus, the cyclic voltammetry system  130  employed was reliable.  T a b l e 2-9. Redox potentials of p-substituted ^?gjQ-tetraphenylporphyrins in C H C l . 2  „  ,  .  Potential (V vs. S C E ) £-(3)  H T P P (2a) c f H TPP ( 2a)' d H TPP(CF ) ( 4 6 a )  -  HTPP(CF)(47a) H TPP(CF ) ( 4 8 a )  1.46 1.40  d  2  2  2  3  2  d  33  2  d  2  3  4  H TPP(CF ) (CF CF ) d H TPP(CH ) ( 5 7 a ) d H TPP(CH ) ( 5 8 a ) 2  3  3  2  2  3  2  2  3  3  3  ( 5 2 a ) d  HTPP(CH)(59a)  d  34  2  H T P P ( C N ) (32a, x=2) H T P P ( C N ) (32a, x=3)  E-(2) 1.34 1.35  E°; (l)  -  -  1.54  b  Eff (2)  AE (1)  -1.56 -1.55 -1.28 -0.77 -1.60 -1.59 -1.60 -1.01 -0.61  2.23 2.22 2.06 1.63 1.42  2  -1.20 -0.97 -0.61 -0.47  f  1.22 1.30 1.25  -  2  1.01 1.02 1.09 1.02 0.95 0.93 0.94 0.88 0.81 1.32  e  1.13 1.03 0.94 1.41  Eff (l) -1.22  2  f  -0.27 -1.28 -1.29 -1.30 -0.71 -0.50 -0.23  a  2  C  1/2  f  1.20 2.22 2.17 2.12  2.03 1.86 H T P P ( C N ) (32a, x=4) 1.66 "Experimental conditions: [porphyrin] = 0.5 m M ; [ T B A P F J = 0.1 M ; scan rate = 0.05 V / s ; e  2  2  2  3  2  4  c  1.36 1.43  e  reference electrode = A g wire. Potentials were determined by referencing to the internal standard of ferrocene/ferrocenium redox couple (0.46 V vs. S C E , CH Cl 2i3). E , ° ( n ) a n d E, / (n) are n th b  2  2  r  2  2  oxidation and reduction potential respectively. ( E + E ) / 2 are reported, where E pc  pa  p c  and E  p a  are  the cathodic and anodic peak potentials, respectively . AE (1) = E ° ( l ) - E, (1); H O M O c  rc  1/2  / 2  /2  L U M O gap. This work. R e £ 1 6 1 . R e £ 1 5 6 .  The H TPP(CF ) 2  H T P P (2a). 2  3  d  c  reduction  potentials  3  f  of  the  p-tiifluoromethylporphyrins  (H TPP(CF ) 2  3  2  ( 4 6 a ) ,  ( 4 7 a ) , H TPP(CF ) ( 4 8 a ) , and H T P P ( C F ) ( C F C F ) ( 5 2 a ) ) are higher than that of 2  3  4  2  3  The positively shifted reduction potentials  3  2  3  are due to the strong electron-  withdrawing effect of - C F groups. A similar phenomenon is observed for a series of 3  141  p-cyanoporphyrins (32a,  x = 2-4). 1^1 The reduction potentials of these porphyrins are higher  than those of P-trifluoromethylporphyrins, indicating the difference in electron-witEdrawing strength between - C F and - C N groups. Electrochemical studies regarding P-substituted 3  /W^o-tetraarylporphyrins showed the first reduction potential of the macrocycle linearly changes with the electronic effect of a substituent and it does not depend on the structure of the macrocycle. 1 ° 1 - 1 6 5  implies that the electronic effects of pyrrolic P-substituents should be  reflected in the difference in the first reduction potentials. The changes in the first reduction potentials from 2a to 48a difference between 48a potentials of 46a  and to 32a  and 32a  and 32a  (x = 4) are 0.75 V and 0.99 V,  is 0.24 V.  (x = 2) and 47a  respectively and the  Similar analysis concerning the first reduction and 32a  (x = 3) results in 0.26 V and 0.11 V,  respectively for the differences between P-trifluoromethyl- and —methylporphyrins. Thus, it is estimated that the difference in the electron-withdrawing strength between —CF and —CN 3  groups causes approximately a 0.2 V difference in the first reduction potential. O n the other hand, the oxidation potentials of P-trifluoromethylporphyrins 46a,  47a,  48a,  and 52a are more or  less same as those of 2a, while those of P-cyanoporphyrins (32a,  x = 2-4) are obviously higher  than those of 2a. As discussed in Chapter I, section D.2.£.(2), oxidation of the macrocycle is sensitive to distortion of the macrocycle. Thus, it is probable that the electron-withdrawing effects of —CF groups are offset by macrocycle distortion caused by the steric interaction 3  between the P-trifluoromethyl groups and the meso-pehnyl groups (We will discuss macrocycle  distortion  Zn(TPP(CF ) ) (48b) 3  4  H T P P ( C F ) (48a) 2  3  4  in  detail  in  the  analysis  of  an  X-ray  crystal  structure  the of  in section B.4.b(3)). A n estimation of the first oxidation potential of barring macrocycle distortion would be approximately 0.2 V higher (i.e.  ~ 1.15 V) according to the analysis concerning the first reduction potentials.  142  A n interesting observation is the H O M O - L U M O gap (AE (1) difference between the 1/2  first oxidation and the first reduction potentials, Table 2-9). This progressively decreases as the number of —CF groups increases even when the offset of oxidation potentials is considered. A 3  similar phenomenon is also observed in a series of P-cyanoporphyrins (32a, other  hand,  such  HOMO-LUMO  p-methylporphyrins (H TPP(CH ) 2  3  2  gap  contraction is  not  x = 2-4). 161 O n the  observed  for  58a,  of  ( 5 7 a ) , H TPP(CH ) ( 5 8 a ) , H TPP(CH ) ( 5 9 a ) . Figure 2-26 2  3  3  2  3  shows the plots of the first redox potentials of p-ttifluoromethylporphyrins (46a, and P-methylporphyrins (57a,  a series  59a)  4  47a,  and  48a)  against the number (n) of the pyrrolic P-substituents  (-CF or —CH ). The plot ofthe first oxidation potentials of P-trifluoromethylporphyrins (•) has 3  3  a maximum at n = 2. In contrast, the first reduction potential (o) increases almost linearly. It seems to fit a sigmoid curve better. Further discussion on this is not possible because the potentials for n = 1 is not available for now. The deviation of the oxidation potential at n = 4 from the predicted linearity (dotted line) made by the points at n = 0 and n = 2 is 0.22 V . This value may be reflecting distortion of the macrocycle in 48a.  Even if we consider the effect of a  presumed macrocycle distortion, the difference between the first oxidation and reduction potentials (i.e. the H O M O - L U M O gap) obviously decreases as the number of —CF groups 3  increases. The first oxidation (•) and reduction (o) potentials of p-methylporphyrins, on the other hand, change linearly as the number of methyl groups increases and the H O M O - L U M O gap parallels. These observations imply that the H O M O - L U M O gap contraction for a series of P-trifluoromethyl- and P-cycanoporphyrins is due to strong electron-withdrawing effects of —CF  3  and —CN groups. This phenomenon can be also rationalized by the unique electronic  F i g u r e2 2 6 .R e d o xp o t e n t i a l so f( a )H TPP(CF )( x=0( 2 a ) ,2( 4 6 a ) , 3( 4 7 a ) ,a n d4( 4 8 a ) )a n d( b )H TPP(CH )( x=0( 2 a ) ,2( 5 7 a ) ,3 ( 5 8 a a n d4( 5 9 a ) ) . S y m b o s l in t h eg r a p h si n d i c a t ed i f f e r e n t e e lc t r o d er e a c t i o n s ; • : 1s to x i d a t i o na n d O :1 s tr e d u c t i o n . 2  2  3 X  3 X  144  structure of P-tiifluoromethylporphyrins as shown in the analysis of UV-visible and N M R spectra. Figure 2-27 shows the energy level diagram for H O M O s and L U M O s  of the four  generic metalloporphyrin classes.205 According to this diagram, as the macrocycle is reduced the H O M O - L U M O gap progressively contracts. The gap of bacteriochlorin, in which the 1871electron pathway is fixed due to the reduced pyrroles in antipodal positions, displays about 60 % of  resonance  compared to  that  of  a porphyrin.  P-Trifluoromethylporphyrins have  a  bacterichlorin-type fixed 18TC-electron pathway (see Figure 2-16) and the distorted electronic pathway probably leads to the narrow H O M O - L U M O  gap for which strong electron-  withdrawing groups must reside on the pyrrolic P-positions of pyrroles in antipodal positions.  b. Zn(II) porphyrins Many of the electrochemical studies of porphyrins have shown the redox potentials of Zn(II) porphyrins. Thus investigation of Zn(II) porphyrin redox properties is advantageous for comparison with those of other porphyrin macrocycles. In this section the redox potentials of p-tetralds(tofluorometJiyl)-^j-o-tetj:aphenylporphyrinato Zn(II)  (Zn(TPP(CF ) )) (48b) 3  4  are  reported and compared with those of other selected Zn(II) porphyrin systems. Figure 2-28(a) shows the  cyclic voltammogram of Zn(TPP(CF ) ) (48b) 3  4  in CH C1 . 2  Unlike  2  the cyclic  voltammetry of the corresponding free-base, two one-electron oxidations and clean two oneelectron reductions were observed. Under the same condition, redox potentials of Zn(TPP) Zn(TPPBr ) 4  ( 4 5 b ) , and Zn(TPP(CH ) ) (59b) 3  4  (2b),  were also measured and the redox potentials of  these porphyrins are summarized in Table 2-10 with those of other electron-deficient porphyrins reported in the literature. In Figure 2-28(b), the first oxidation and the first reduction potentials of  P-tetrasubstituted  ^.ro-tetaphenylporphyrins including Zn(TPP(CN) ) (32b, 4  x = 4)  were  plotted against the 4o~ value (Table 1-3 in Chapter I, section BJ.b.(l) for o~ values for each p  p  145  -8 r >  -9 —  LUM0(TT*)  >. 00  -10 •••H-  HOMO(TC)  O  -11  -12  P o r p h y r n i  C h l o r i n  I s o b a c t e r i o c h l o r i n  B a c t e r i o c h l o r i n  Zn c o m p e lx e s  F i g u r e 2-27.  Energy level diagram for H O M O s and L U M O s of the four  generic porphyrin classes. Adapted from ref.205.  146  (a)  2.0  1.0  -1.0  0.0  -2.0  Potential ( V vs. S C E )  (b)  2  4a  F i g u r e 2-28. [48b]  (a) Cyclic v o l t a m m o g r a m o f Z n ( T P P ( C F ) ) 3  = 1 x 10 " M , [ T B A P F ] = 1 x 10 3  6  _1  4  ( 4 8 b ) . Solvent: C H C 1 , 2  2  M , scan rate: 50 m V / s . T h e white arrow  indicates ferrocene/ferrocenium couple, (b) 4 a vs. 1st oxidation ( • ) and 1st reduction (O) (Zn(TPP)  (2b),  potentials o f P-tettasubstituted /mo-tettaphenylporphyrinato Zn(II) ZnCTPP(CN) ) 4  (34b,  x=4), Z n ( T P P B r ) 4  ( 4 5 b ) , ZnCTPP(CF ) ) ( 4 8 b ) ) . 3  4  147  T a b l e 2-10. Redox potentials of |3-substituted ^ao-teteaphenylporphyrin Zn(II) complexes in CH C1 . 2  2  Potential (V vs. SCE)  Porphyrin  E,°; (2)  Zn(TPP) (2b) c  d  Zn(TPFPPBr ) (8b) b Zn(TPPBr ) ( 4 5 b ) c Zn(TPPBr ) ( 4 5 b ) d  8  4  4  Zn(TPPBr ) (7b) c  8  Zn(TPP(CF ) ) ( 4 8 b ) b  3  Zn((CF ) P) 3  4  4  ( 1 6 b ) e  b  4  ( 3 2 a ) f  Zn(TPP(CN) ) 4  0.83 -  .1.11  -  Zn(TPP(CH ) ) ( 5 9 b ) 3  0.80 0.78 1.38 1.37 1.57 0.93 0.90 0.85 0.92 1.44 0.71  1.64 1.58 1.53 1.10 1.14 1.11 1.24  b  ZnCTDCPP^O^,) ( 1 5 b ) g  E$(2)  AE (1)  -1.40 -1.39 -0.99  -  2.20 2.17  2  1.12 1.11  Zn(TPP) (2b) Zn(TPFPP) (4b) Zn(TPFPP) (4b)  Ev (l) d  2  b  -  1/2  -1.84 -1.36 -1.37 -0.76 -1.30 -1.36 -1.10 -0.81  -0.95 -0.48 -1.08 -1.09 -0.85 -0.58 -0.71 -1.50 -0.44 0.16  -  a  2.37 2.32 2.03 2.01 1.99 1.70 1.50 2.15 2.21 1.55  -  -  -  E ° (n)and E " (n) are n th oxidation and reduction potential respectively. AE (1)= E,°; (1)- E\% (1); H O M O - L U M O gap. This work. Experimental conditions: [porphyrin]: 0.5 or 1 m M ; [TBAPF ]:0.1 M ; scan rate: 0.05 V / s ; reference electrode: A g wire. Potentials were determined by the internal standard of  a  / 2  2  1/2  2  b  6  ferrocene/ferrocenium redox couple (0.46 V vs. S C E , C H ^ h ) . are vs A g . A g C l . Ref.39. In benzonitrile. Ref.161. Ref.37. c  group).  Since  each  f  of Zn(TPPBr ) 4  2 1 3  d  Ref.214 Values  ( 4 5 b ) , Zn(TPP(CF ) ) ( 4 8 b ) , Zn(TPP(CH ) ) ( 5 9 b ) , 3  4  p  4  3  4  values were used instead of a  values. As shown in the figure, the first oxidation potentials  4  Ref.164.  8  Zn(TPP(CN) ) (32b, x = 4) contains four (3-substituents, 4 a  Zn(TPP)(2b), Zn(TPPBr ) ( 4 5 b )  c  p  o f Zn(TPP(CH ) ) 3  4  ( 5 9 b ) ,  and Zn(TPP(CN) ) (32b, x = 4) are on a slightly curved line. 4  However, the oxidation potential for 4 8 b is slightly lower than the line by about 0.2 V , which is similar to the deviation of Figure 2-26(a). The plots of the first reduction potentials show an interesting result. Previous studies^°2-164 h s  o w e  d that reduction potentials linearly changed as  the number of bromines on the P-pyrrolic positions increased. Thus we can expect that change in the first reduction potential of porphyrins is proportional to the sum of the rj values of the p  substituents. However, as shown in Figure 2-28(b), the plot of the reduction potentials against  148  the CT values in the series of (3-tetrasubstituted /#£ro-tettaphenylporphyrinato Zn(II) shows a p  gentle sigmoid curve. The oxidation potentials, except for that of - C F , may also fit a sigmoid 3  curve, but the change in the oxidation potentials is too small to argue this point. Unfortunately, the number of the data shown in Figure 2-28(b) is limited but the plots show that both oxidation and reduction potentials are leveling off at higher 4cj values and leading to a fixed and narrow p  H O M O - L U M O gap. This indicates that the electronic structure of the macrocycle converges into a bacteriochlorin-type structure due to strong electron-withdrawing effects of substituents on the antipodal pyrroles. O n the other hand, at lower 4 a values (i.e. for Zn(TPP(CH ) ) p  the H O M O - L U M O gap is as wide as that of Zn(TPP) (2a).  3  4  ( 5 9 a ) )  This result matches the observations  of P-trifluoromethylporphyrins by the UV-visible and N M R spectroscopies.  In order to compare P-tetealds(tiifluoromethyl)porphyrinato Zn(II) with other Zn(II) porphyrins in Table 2-10, the first oxidation and the first reduction potentials are plotted in Figure 2-29. As shown in Chapter I, the reduction potential reflects the electron-deficiency. Thus, a high reduction potential of a porphyrin indicates that the porphyrin is electron-deficient. This simple analysis ranks Zn(TPP(CF ) ) (48b) 3  more  electron-deficient  Zn(TPPBr ) (7b), 8  than  4  porphyrin  as an electron-deficient porphyrin. It seems Zn(TPFPP) (4b)  and as electron-deficient as Zn(TPFPPBr ) (8b). 8  (see  Figure 1-8, p i 1)  and  This latter macrocycle is well  known in the third generation porphyrin catalysts (see Chapter I, section B.Zd). For better robustness as an oxidation catalyst, a higher oxidation potential is desired, but the oxidation potential of Zn(TPP(CF ) ) (48b) 3  potential of 48b  4  is the same as that of Zn(TPP) (2b).  Thus, the high reduction  may be a good indication that it may be advantageous to activate a central metal  in porphyrin catalysts. Metal complexes such as Fe(III) or Mn(III) porphyrins may give a small  149  L U M P of ZnTPP  H O M O of ZnTPP  V  V (2b)  ZnTPP  ZnTPPBr (45b)  •  p  ^ .  h  4  ZnTPPBr  z  h  ^  P  h  sr  x  -fh  (7b) b  8  (4b)  ZnTPFPP  ZnTPFPPBr  ZnTPP(CF ) (48b)  •  :  3  (8b) c  8  ? h  Ph-  4  FC 3  ZnTPP(CH ) 3  (59b)  4  ZnTPP(CN)  •  (34b)  4  Zn(CF3) P 4  ( 1 6 b ) e  t\l0  2  o ZnTDGPPQSlO^g (15b/  0  tfC>2  \ f 0 N2  - v_  Ar—(  -1  CN Ph  N y  ^Zh(ll) >-C H CI (=Ar) 6  3  2  1  Potential (V)  a  F i g u r e 2-29. The H O M O (•: 1st oxidation)-LUMO (O: 1st reduction) gap of P-substituted mro-arylporphyrin Zn(II) complexes. Potentials are in vs. S C E for 3  2b, 4b, 7b, 15b,  16b,  34b,  45b,  48b,  and 59b  Data were measured in C H C 1 except for 16b, 2  b  Ref.75. Ref.214. c  d  2  and in vs. A g / A g C l for 8b and  Ref.161. R e £ 3 9 . Ref.37. e  f  12b.  which was measured in benzonitrile.  Br  150  gain in the oxidation potential. This would be an unsatisfactory result for a robust oxidation catalyst.  The high reduction and the low oxidation potential of Zn(TPP(CF ) ) (48b) 3  4  result in a  narrow H O M O - L U M O gap. In Figure 2-29, the numbers between the oxidation and the reduction show the H O M O - L U M O gaps for various Zn(II) porphyrins in volts while the two dotted lines are the H O M O and the L U M O of Zn(TPP) (2a). gaps of 48b  and Zn(TPP(CN) ) (32b, 4  x = 4) are narrower than those of other electron-deficient gaps of Zn((CF ) P) (16b,  porphyrins. Since the H O M O - L U M O Zn(TPPBr ) 4  Obviously, the H O M O - L U M O  3  ( 4 5 b ) , and Zn(TPP(CH,) ) (59b) 4  4  are close to that of  n=  1) (Figure 1-8,  p.ll),  2a, it is obvious that both  symmetry and strong electton-witlidrawing substituents are required for the narrow H O M O L U M O gap. The reason for this, as explained for the free-base porphyrins, is that the macrocycles of 48b  and 32b  (x = 4) presumably have the bacteriochlorin-like fixed 187t-electron,  pathway. In addition to the distorted electronic pathway of the macrocycle, offset of the oxidation potential by the macrocycle distortion 44-146 i  H O M O - L U M O gap of  m  a  v  a  j  s o  contribute to the narrow  48b.  In summary, the electron-withdrawing effects of —CF groups on the pyrrolic P-positions 3  increased the reduction potentials of P-trifluoromethylporphyrins almost linearly as the number of —CF groups increased. The first oxidation potential did not gain much from that of 3  /Wwo-tetraphenylporphyrin and a linear increase of the potential with the number of —CF groups 3  was not obtained due to the offset by a presumed macrocycle distortion. Narrowing of the H O M O - L U M O gap was observed as the number of —CF groups increased. This is presumably 3  because the macrocycle is forced to take a distorted 1871-electton pathway just like that of  151  bacteriocMorin by the strong electton-withdrawing effect of —CF groups on the antipodal 3  P-Tettakis(trifluoromethyl)porphyrin (48)  pyrroles.  may  be  as  electron-deficient  as  the  porphyrins appeared in the tliird generation porphyrin catalysts such as P-octabromo-#?£rotetrakis(perfluorophenyl)porphyrin (TPFPPIkg) (8) (Figure 1-8, p.11) but the oxidation potential of 48 seems to be insufficient for a robust oxidation catalyst.  c. Fe(III) porphyrins In the past, redox potentials of Fe porphyrins were used to discuss the activity and the stability of the porphyrins as oxidation catalysts.45,73 j complexes  of  P-trifluoromethylporphyrins  Fe(TPP(CF ) (CF CF )Cl 3  3  2  3  n  this section redox potentials of Fe(III) (Fe(TPP(CF ) )Cl (48f) 3  and  4  ( 5 2 c ) ) measured by cyclic voltammetry are reported and they are  compared with those of other selected Fe(IIF) porphyrins. Table 2-11 summarizes the redox potentials of Fe(IIi) porphyrin chloride complexes. Cyclic voltammetry measurements with known porphyrins, Fe(TPP)Cl (2d)  (Figure 1-8, p . l l ) and Fe(TPPBr )Cl (45e) 4  (Scheme 2-8)  showed that the measured values were close to the reported values. The first reduction potentials (Fe(III/II) couple) for 48f and 52c the  same  as  that  (Fe((C F ) P)Cl) (16d) 3  7  4  of  the  shifted positively about 0.3 - 0.4 V from that of 2d and are as  wwo-tetrakis(heptafluoropropyl)porphyrinato  (Figure 1-8). The Fe(III/II) couples of 48f  the values of the second generation catalyst, Fe(TPFPP)Cl (4d) generation catalyst, Fe(TPFPPBr )Cl (8d) 8  and 52c  and 52c  Fe(III)  chloride  are ranked between  (Figure 1-8) and the third  (Figure 1-8). Thus, redox tuning of the Fe(III) in  48f  seems to be successful for modelling P-450 compounds. However, the first oxidation  potentials of 48f  and 52c  are the same level of as that of 2d.  This may imply that these  porphyrins will not perform as robust oxidation catalyts. The reason for the low oxidation potentials in 48f and 52c must be the macrocycle distortion as discussed in the previous sections.  152  PH  PL, PH  PH  PH PH  c/5  <<  a  j u X #  o co  CJ  QH  PH PH  <! <^ CQ  PH  PH  PH  PH  PH PH PH PH  PH  PH PH  <1 <I <J <1<  <  EE E  EE  za z 2 ^  £  PH PH C J  5?  PH  CJ  5?  PI  ^ u  £ ?P PH  U  SH C J  M.  oo  cq  O  rn  so  vo O  o  o  CJ  PH  cn  HH  PH  PH  CJ  00 CN  oo o  o  CN CN  Tt-  oo  o  z  z cj  oz ^  02 u  O CN CN T-H cn C7i O C \ C \ T-H o  PH  Th  o  O  m  SO  T"H T-H  ^3 (N so Cs CO O t • m ro to CN T-H (M o o o  o u  d  d  o  d  d  d  "2; so P  °  o d  T-H  o VH d d  O  p  T-H  P  O  CN  CN  d  <u a  o o u  o  CN  PH  00 H  CO H  SO (S|  m oo ^  h  cn  >  00 d  JJ  e-  o a  CN t— m  m  m  CN  CO  m m  O so co so i n so  00 SO  cn m  oo  u  o  II  CU PH  u  CN  m U  a CU  (3^  +H  aOx o -a PH  •d  o PH  CN  C4  H  T3  u pT PH  oo  CN  m  PH CJ,  U PP  cu  PH  PH CJ  PH CJ,  PH  1)  PH  m PH  T3\-  CN  '  £js  m "d -— so •d  cj^  U  PH PH  y CJ  CJ  & PH  PH  o  1 1  PH ' PH PH PH  PH PH"  T3  go,  p? P7 PQ PH  cy PH  0  •d  m  T-H  CN cu  PH  153  However, as shown in Table 2-11 the first oxidation potential of one of the third generation porphyrin  catalysts,  Fe(TDCPPCl )Cl (lOd) 8  (Figure 1-8),  is even  lower  than  that o f  Fe(TPP)Cl (2d) (Figure 1-8). It is not easy to predict the catalytic activity of 48f and 5 2 c from the redox properties alone. Accordingly, actual oxidation reactions have to be run to investigate the efficacy of these Fe(III) porphyrins as catalysts.  4. Crystal structures In this section, the X-ray crystal structures of Zn(II) complexes o f P-tetrasubstituted ^-teteaphenylporphyrins (Zn(TPPBr ) ( 4 5 b ) , Zn(TPP(CF ) ) (48b) and Zn(TPP(CH ) ) ( 5 9 b ) ) 4  3  4  3  4  are reported. These X-ray crystal structures are very important not only to elucidate the structures of the macrocycles but also to support discussions presented for the UV-visible, N M R spectroscopic and electrochemical studies of the p-trifluoromethylporphyrins. These discussions suggested a fixed 187t-electron pathway (Figure 2-16) and the macrocycle distortion as dominant electronic and structural characteristics. O f specific interest are the steric effects of - C F groups. 3  Therefore, in the second part o f this section analysis of distortion of the macrocycle of Zn(TPP(CF ) ) (48b) is focused. 3  4  a. Preparation of the crystals and crystallographic data. Zn(TPP(CF ) ) (48b) 3  4  was crystallized as Zn(TPP(CF ) )-(EtOH) 3  4  3  (48b-(EtOH)) from a 3  mixture of E t O H and CHC1 . In addition to X-ray crystallography, the crystals were analyzed by 3  *H and  1 9  F N M R solution spectroscopy and elemental analysis. The 200 M H z  'H NMR  spectrum of 48b-(EtOH) in CDC1 showed that E t O H signals shifted to the higher field than 3  3  those of the normal E t O H in CDC1  3  at room temperature, suggesting a shielding effect by  porphyrin. Attempts to crystallize out Zn(TPPBr ) (45b) 4  and Zn(TPP(CH ) ) (59b) 3  4  from the  same solvent system failed due to their low solubility in E t O H / C H C 1 . Accordingly, porphyrin 3  154  4 5 b was crystallized as Zn(TPPBr )• (MeOH)• (DMF) to give the solvate 45b-(MeOH)-(DMF) by 4  slow diffusion of M e O H into the D M F solution. The compound 5 9 b was crystallized as Zn(TPP(CH ) )-(THF) -(CHCl ) 3  4  16  3  (59b-CTHF) -(CHCl) )  04  16  by slow  3 04  evaporation  from  C H C L / T H F . These single crystals were analyzed by *H N M R solution spectroscopy and elemental analysis as well as by X-ray crystallography. Table 2-12 shows crystallographic data.  The three Zn(II) porphyrins showed square pyramidal coordinationforthe central Zn(II) atoms. In the crystal structure of 45b-(MeOH)-(DMF) and 48b-(EtOH), a M e O H molecule and 3  a E t O H molecule are coordinated to Zn(II) atoms, respectively. In 59b-(THF) -(CHCl ) , T H F 16  3 04  coordinated to Zn(II) and disordered structure was observedforthe axial T H F . In addition, two different solvents, T H F and CHC1 appear to occupy the same volume 60 % and 40 % of the 3  time respectively. Details of the structures of these complexes are described in the following section.  T a b l e 2-12. Crystallographic datafor45b-(MeOH)-(DMF), 48b-(EtOH), and 3  59b-fTHF) , -(CHCl ) 1 6  3 ft4  Empirical formula F.W. space group a, A b,A c,A  <x,°  !V Y,° v,A z D  3  (g/cm ) 3  c a k  u. (Mo-Ka) (cm- ) T (°C) 1  No. of observations R(F)  45b-(MeOH)-(DMF)  48b-(EtOH),  59b-CrHF) ;(CHCl,)o,  C H, Br N 0 Zn 1098.83  C H F N 0 Zn 1088.31  C54.80 ^49.2oN Zn0 . Cl  P 1 12.257(2) 13.4377(8) 14.387(1) 83.819(2)  p 12.0428(11) 13.275(2) 16.909(2) 96.951(5)  P2,/n  71.227(2)  108.124(2)  93.274(3)  4 8  5  4  5  2  5 4  4 2  1 2  T  4  1/  3  r  4  897.34 13.585(1) 18.182(1) 18.065(2)  73.575(3)  107.354(2)  2151.7(3) 2 1.70 43.42  2383.2(5) 2 1.52 6.13  4454.9(6) 4 1.34 6.70  -100 ± 1 6086 0.058 0.089  -93 ± 1 5823 0.099 0.091  -100 ± 1 2621 0.129 0.155  1  60  155  b. Structure details O R T E P views (in 30 % probability ellipsoid) of the crystal structures are shown in Figure 2-30-45b, Figure 2-30-48b, and Figure 2-30-59b. Each figure shows the top view and the side view. Solvent molecules for the top views and meso-phenyl groups and part of the solvent molecules for the side views were omitted for clarity. Selected bond lengths and bond angles for the  shown  structures  are  Z n ( T P P ) ( H 0 ) (2a-(H 0)) 16 2  2  2  a r  summarized  in  Table 2-13.  Structural  data  for  e also listed in the table for comparison. Some designations  used in Table 2-13 are shown in the molecular diagram in Scheme 2-10.  R = H (2b) = Br (45b) = C F (48b) = C H (59b) 3  3  S c h e m e 2-10. Atom designations used in Table 2-13.  (1) Core si%e, Zn displacement, and axial coordination Coordination around Zn(II) in complexes 45b(MeOH)-(DMF), 48b-(EtOH), and 3  59b-(THF) -(CHCl ) is penta-coordinate square pyramidal. This structure is common for 16  3 04  Zn(II) porphyrins. ! ^ In complexes 45b, 48b, and 59b, the Zn(II) atoms are displaced by 0.277, 2  0.325, and 0.234 A from the least-square plane through the four porphyrin nitrogen atoms ( N plane),  respectively.  These  values  are larger  than  the  0.173 A  4  reported for  Zn(TPP)-(H 0) (2a-(H 0)). 16 The macrocycle core sizes (N—Cr, where Ct is the centroid of 2  2  2  the four nitrogen atoms. Table 2-13 for the details.) of Zn(TBBBr ) ( 4 5 b ) , Zn(TPP(CF ) ) ( 4 8 b ) , 4  3  4  156  F i g u r e2 3 0 4 5 b . X-ray crystal structures of 45b- (MeOH)- (DMF). The axial ligand and the solvent molecule for the top view and the meso-xphenyl groups for the side view were omitted for clarity.  F i g u r e2 3 0 4 8 b . X-ray crystal structures of 48b- ( E t O H ) . The axial ligand and 3  the solvent molecules for the top view and the meso-phenjl groups and solvent molecules for the side view were omitted for clarity.  158  F i g u r e2 3 0 5 9 b . X-ray crystal structures of 59b- (THF), - (CHC1 ) . The axial ligand and 6  3 04  the solvent molecules for the top view and the meso-phenyl groups and solvent molecules for the side view were omitted for clarity.  159  T a b l e 2-13. Core size, selected bond lengths and bond angles. Selected bonds" N—Ct,  N1 N3  N'  Zn(TPPBr ) 4  (45b)  3  4  Zn(TPP(CH ) )  Zn(TPP)  (59b)  (2b)  3  (48b)  4  b  Core size (A)  C f  Ct Ct  ZnCrPP(CF ) ) d  2.097 2.090  2.105 2.108  2.076 2.076  N2  Ct  2.012  1.976  2.013  N4  Ct  2.006  1.949  2.010  2.043  Bond length (A)  Zn-O Zn-N,  2.108(MeOH)  Zn-N  2.110(EtOH)  2.182(THF)  Zn1-N1, Zn1-N3  2.121,2.109  2.130,2.108  2.091, 2.092  Znl-N2, Znl-N4  2.030, 2.021  2.008, 1.997  2.024, 2.020  N1-C1, N1-C4 N3-C11,N3-C14  1.371, 1.374 1.383, 1.371  1.379, 1.378 1.365, 1.374  1.356, 1.385 1.375, 1.384  N2-C6, N2-C9 N4-C16, N4-C19  1.372,1.369 1.365,1.375  1.382,1.380 1.384,1.378  1.380,1.380 1.379,1.368  C1-C2, C4-C3 C11-C12, C14-C13  1.451, 1.449 1.448, 1.446  1.462, 1.445 1.439, 1.459  1.453, 1.447 1.468, 1.454  C6-C7, C9-C8 C16-C17, C19-C18  1.445,1.450 1.449,1.439  1.445,1.445 1.446, 1.464  1.454,1.449 1.443,1.470  C2-C3, C12-C13  1.357, 1.344  1.371, 1.366  1.382, 1.369  C7-C8, C17-C18  1.342,1.346  1.335,1.337  1.337,1.358  C1-C20, C4-C5 C11-C10, C14-C15  1.408, 1.411 1.411, 1.405  1.424, 1.404 1.445, 1.414  1.428, 1.417 1.408, 1.423  C19-C20, C6-C5 C9-C10,C16-C15  1.405,1.400  1.386,1.401 1.407,1.392  1.394,1.394 1.391,1.374  N-Ca,  2.228(H Q) 2  ,c  N'-C '  2.050  c  a  CcrCp, C ' - C p '  1.374,1.369  c  a  Cp-Cp, C p ' - C p '  1.441,1.443  c  1.395,1.405  Selected angles  1.341  1.405  Bond anj les 0  3  ?  N-Zn-N, N ' - Z n - N '  N1-Zn1-N3  163.9  166.8  165.9  N2-Znl-N4  165.4  156.8  168.1  CcrN-Ca,  170.3  Ca'-N-Ca"-'  C1-N1-C4,C11-N3-C14  108.5, 107.8  108.2, 108.1  105.2, 106.6  C6-N2-C9, C16-N4-C19  107.1,106.2  106.3,107.4  106.9,108.0  106.8 (continued)  160  T a b l e 2-13  (continued) Zn(TPPBr )  Zn(TPP(CF ) )  ZnCTPP(CH ) )  Zn(TPP)  (45b)  (48b)  (59b)  (2b)  4  Selected angles"  3  4  3  4  b  Bond an gles 0  CyCVA/, C ' - C ' - N ' C2-C1-N1, C3-C4-N1 C12-C11-N3, C13-C14-N3  108.7, 107.9 108.7, 108.1 111.9, 110.9 108.0, 108.5 109.4, 108.1 109.8, 109.8  C7-C6-N2, C8-C9-N2 C17-C16-N4, C18-C19-N4  108.9,109.2 110.0,109.8  e  p  CorCp-Cp,  a  C '-Cp'-Cp'  109.1,109.3 108.3,108.5  109.1,108.6 108.9,108.6  109.3  c  a  C1-C2-C3, C4-C3-C2 106.8, 108.1 106.2, 108.1 105.6, 106.3 C11-C12-C13, C14-C13-C12 107.9, 107.6 106.8, 107.2 106.4, 107.2 C6-C7-C8, C9-C8-C7 C16-C17-C18, C19-C18-C17  107.8,107.0 106.7,107.3  107.7,107.5 108.6,106.9  107.1,108.3 107.9,106.6  CcrCmeso~Cpby CQ?-Cmeso-Cph ^ C1-C20-C , C4-C5-C 119.1, 118.6 121.0, 117.6 119.3, 117.7 C11-C10-C ,C14-C15-C 118.3, 118.6 118.3, 121.8 118.4, 117.2  107.5  0  pU  ph1  hh2  hhi  C19-C20-C , C 6 - C 5 - C ph4  phl  C9-C10-C , C16-C15-C nh2  Ca-Cmeso-Ca'  oh3  115.4,116.4 116.3,116.0  114.7,117.4 117.8,113.2  115.7,115.8 115.4,117.3  125.5,124.8 125.4,125.4  124.3,124.5 123.7,125.0  124.9,126.5 126.2,125.5  129.5 128.7 129.6  128.6 124.2 125.7 129.3  129.6 129.5 127.6 128.3  117.2  6  C1-C20-C19, C4-C5-C6 C9-C10-C11,C14-C15-C16  N.A.  C -Cp-R * e  a  C1-C2-R C4-C3-R C11-C12-R C14-C13-R a  129.6  See Figure 2-30-45b, 48b  and 59b  for atom designations. Ref. 216. Ct is the centroid of the b  c  d — [^(x^xj + b (y -y^) +c (^ -^ ) + 2bc-cosa{y j^)(^-t^) + 2ca-cosR(^-^)(x x^) +2ab-cosy{x x^){y j )] , where d is the distance between coordinates ( uji, Ki) ( i,j2, Scheme 2-10 for N , N ' , C , C ' , Cp, Cp', C , and C designations. four nitrogens.  2  Calculated using  d  2  2  x  2  2  J  2  r  i/2  r  x  a  n  d  r  x  e S  e  r  2  e  a  a  mta  p h  Cph,: C21 for 45b, C25 for 48b and 59b, C : C27 for 45b and C31 for 48b and 59b, C : C33 for 45b and C37 for 48b and 59b, C : C39 for 45b and C43 for 48b and 59b. R: Br for 45b, C F for 48b, and C H for 59b. f  p h 2  p h 3  8  p h 4  3  3  and Zn(TPP(CH ) ) (59b) 3  reported in  italic  obviously  larger  4  in the direction of P-substituted pyrroles (values in this direction are  in Table 2-13; than  those  N- • -Ct (average) in  the  =  direction  2.048, 2.106, of  and  non-substituted  2.076K  respectively) are  pyrroles ( N ' - C t  (average) = 2.009, 1.962, and 2.012 A respectively) and the core sizes in the direction of non-  161  substituted pyrroles of 4 5 b , 4 8 b , and 5 9 b are smaller than that ( C t - N (2.043 A)) o f the macrocycle in Zn(TPP)-(H 0) (2a-(H 0)).  216  2  2  The largest Zn(II) displacement from the N  4  plane in 4 8 b may be due to the smallest N---Ct values in the direction of non-substituted pyrroles.  Although the axial ligands for the complexes in Table 2-13 are different, the donor atom in all cases is oxygen. Thus, comparison of Z n - O distance may provide a rough measurement for the electron-deficiency of the porphyrins. The Z n - O distances of 45b-(MeOH) (2.108 A) and 48b-(EtOH) (2.110 A)  are significandy  shorter  than  the 2.228 A  o f Zn(TPP)-(H 0) 2  (2a-(H 0)) or the 2.226 A of Zn(OETPP)-(MeOH) (30) (see p.43 for 30) and comparable 1 4 7  216  2  to the 2.092 A of Z n f T P P F ^ t H p ) (12b-(H0)) (Figure 1-8, p . l lfor1 2 b ) , indicating electron4 1  2  deficiency of the macrocycles of 4 5 b and 4 8 a .  (2) Effects of antipodal B-substitution Antipodally P-substituted porphyrins show unique structural profiles. Firsdy, Z n - N distances (or the core sizes) are longer in the direction of P-substituted pyrroles (see Table 2-13) than in the direction non-substituted pyrrole. In the reported structural studies of antipodally substituted  porphyrins  such  as Ni(TPP(CN) )-(L) (L=py 4  2  or l-Melm) (63), .  (Fe(TPPBr )) 0 (64), or Fe(TPPBr )Cl (45e), similar differences 1 9 2  4  2  1 9 1  4  2 1 92 2 0  in Z n - N distances  between the p-substituted and non-substituted directions were observed. The bond weakening  162  of Z n - N in the P-substituted direction due to electron-wimdrawing effects of the substituents is the rationale for such observations.1^1,219 However, a recent r e v i e w ^ f crystal structures of 2  Q  antipodally P-substituted /^.ro-arylporphyrins suggested there are considerable distortions of the macrocycle cavity due to both electronic and steric effects of the substituents. As shown in Figure 2-31, due to the steric interaction between the P-substituents (R and R) or R and mesophenyl groups, the phenyl groups are pushed away from the R groups. The macrocycle expands in the direction of the P-substituted pyrroles and contracts in the direction of the non-substituted pyrroles. The analysis shown in Figure 2-31 is essential to rationalize a similar observation regarding the Z n - N distances in Zn(TPP(CH ) ) (59b) 3  (Table 2-13) which cannot be explained  4  by the electronic effects of electron-releasing — C H  3  groups. The steric interaction of the  substituents seems to be reflected on the longer Cp-Cp lengths (C2-C3 > C7-C8, Table 2-13) in Zn<TPP(CF ) ) (48b) 3  4  and Zn(TPP(CH ) ) (59b) 3  due to the repulsion between the bulky pyrrolic  4  P-substituents; the effective van der Waals radius of the - C F group is 2.2 3  A  group is 1.8 A ^ 6 . The C2-C3 and C12-C13 lengths in 48b 2  and 59b  126  and that of - C H ,  are significantly longer than  those in Zn(TPP) (2a). In contrast, significant differences in Cp-Cp (C2-C3 vs. C7-C8) bond lengths were not observed for Zn(TPPBr ) ( 4 5 b ) . The van der Waals radius of Br (1.95 A ) ^  2 3  4  nearly as large as that of - C H , but the Cp-Br bond length in 45b  (1.87 A, not shown in  Table 2-13) is much longer than that of Cp-CH in Zn(TPP(CH ) ) (59b)  (1.54 A). The difference  3  3  3  4  is due to the longer Cp-Br lengths. This reduces Br-Br contacts. The C -C -C a  (Table 2-13)  ims  ph  angles  show the steric interaction between meso-phenyl groups and the pyrrolic P~  substituents; wider angles were observed in the direction of the P-substituted pyrroles. Comparison of Cp-Cp lengths in various antipodally P-substituted porphyrins is summarized in  is  N ~ W Steric interaction  Figure 2-31. Schematic illustration of the steric effects of antipodal (5-substituents and meso-phenyl groups on the macrocycle of P-tetrasubstituted OT^o-tetraphenylporphyrin.  164  Table 2-14. In the metalloporphyrins of P-tetrabromo-^Jo-phenylporphyrins 45b  and 45e,  the  difference between the two Cp-Cp lengths is not obvious. The longer Cp-Cp bonds in the direction of P-substituted pyrroles in 59b  and 63 suggest that the bond elongation was caused by  either steric or electron-withdrawing effects. In Zn(TPP(CF ) ) ( 4 8 b ) , it is likely that elongation 3  4  of Cp-Cp bonds occurs due to both effects. The electron-withdrawing effect of —CF group 3  T a b l e 2-14.  Cp-Cp  bond  lengths  in  antipodally  P-tetrasubstituted  ^?gjQ-tetraphenylporphyrins.  Cp-Cp length (A) Porphyrins  P-substituted  P-non-substitued  direction  direction  Zn(TPPBr ) (45b) 1.35 1.34 fFe(TPPBr )]Cl (45e) 1.36 1.35 Zn(TPP(CF ) ) (48b) 1.37 1.34 Zn(TPP(CH ) ) (59b) 1.38 1.35 Ni(TPP(CN) ) (63) 1.37 1.34 Zn(TPP) (2b) 134 This work. Ref.191. Ref.219. Ref.220. Ref.216.  Reference  4  b  4  3  4  3  4  c  4  a  b  c  d  -  d  e  e  presumably leads to a low electron density of the bonds between the pyrrolic P-carbons where the substituents are attached. This Cp-Cp elongation in 48b may direct the 187t-electron to avoid resonance through those double bonds.  (3) Macrocycle distortion Investigation of macrocycle distortion of P-teti:altis(tjifluoromethyl)porphyrin is important in order to rationalize the UV-visible, N M R spectra, and electrochemical data of the porphyrin. Here, distortion of the macrocycle of Zn(TPPBr ) (45b) 4  analyzed.  and Zn(TPP(CH ) ) (59b) 3  4  Zn(TPP(CF ) ) (48b) 3  4  is  compared with that of  and then the mechanism of the distortion is  165  Figure 2-32 shows the degree of distortion in the macrocycles of 45b, 48b, and 59b. The numbers in the porphyrin structures indicates the deviation (in 0.01 A) of each atom from the N  4  mean plane. We can imagine the N plane to be on the page of the figure for the porphyrin 4  structures in the left column. The atoms with positive values are above the page in the porphyrin structures, while atoms with negative values are below the page. The figures beside the porphyrin structures show the skeletal deviations of the 24 core atoms of the macrocycles from the N  4  mean plane. As indicated in Figure 2-32(a), (b), and (c), for all the three macrocycles, pyrrole rings are alternately up and down relative to the N mean plane and thus the macrocycles are 4  saddle-distorted (for general modes of porphyrin distortion refer to the references. 18,145) -ph  e  averages of the absolute values of pyrrolic P-carbon displacements are 0.40, 0.79, and 0.52 A in 45b, 48b, and 59b, respectively. Distortion of the macrocycle observed in 4 5 b and 5 9 b is very similar to that in Z n f T P P F ^ t H p ) (12b-(H0)) (see Figure 1-8, p. 11 for 1 2 b ) which showed 4 1  2  the saddle distortion and the average value, 0.49 A, of pyrrolic P-carbon displacement. In fact, crystal  structures  macrocycle.221  of a four-coordinate  Thus,  it is very  Zn(TPPBr ) ( 4 5 b ) 4  likely  that  shows  the distortion  a planar  porphyrin  o f Zn(TPPBr ) ( 4 5 b ) , 4  Zn(TPP(CH ) ) ( 5 9 b ) , and Zn(TPPF ) ( 1 2 b ) is due to the five-coordinate Zn(II), which is 3  4  8  displaced by 0.23-0.28 A from the N plane. The 0.79 A displacement of pyrrolic P-carbons on 4  average in Zn(TPP(CF ) ) ( 4 8 b ) is obviously larger and this indicates the severe distortion of the 3  4  macrocycle itself. Comparison of the rms (root-mean-square) values (Figure 2-32), which are the average deviations of the 24 core atoms from their least squares plane, also shows the severe distortion in the macrocycle of 48b. The van der Waals (vdW) radius of fluorine is 1.35 1.47 A  1 2 3  estimated  '  1 2 6  , which is close to 1.1-1.3 A of hydrogen. 1  to be 2 . 2 A .  1 2 6  . T h e vdW  radius  of - C F  3  2 3  However, the size of - C F is 3  is estimated  as 2.69-2.81 A  166  (a) ZnCTPPBr ) 4  (b) ZnCTPP(CF ) ) 3  4  (c) ZnCTPP(CH ) ) 3  4  F i g u r e 2-32. Perpendicular atomic displacements of Z n porphyrins (a) 45b, (b) 48b, and (c) 59b,  relative to the N mean plane. The numbers in the porphyrin structures 4  on the left column are the distances in 0.01 A units. The figures on the right column display the skeletal deviations of 24 core atoms of the porphyrins from the N mean 4  plane. • indicates the pyrrolic P-carbons bearing substituents. The rms values show the average deviation of the 24 core atoms from their least squares plane.  167  from the crystallographic data of 48b; +(1.35 to  1.47 A)  3  (vdW of F). Thus, it is probable that - C F is 3  - C H (vdW = 1.8 - 2.0 A)123,126 3  the vdW radius of —CF = 1.34 A(average C - F distance)  a n (  j  s t e  much larger than  r i c interactions among substituents are expected. As  observed in the top view in Figure 2-30-48b, two meso-phenyl groups (C25-C30 and C31-C36) seem to be extremely twisted due to the steric interaction with-CF groups. The average of the 3  torsion angle made by C ^ ( C 2 6 or C30)-C25-C5-C (C4 or C6) is 54.4° and similarly 52.1° for a  the other extremely twisted phenyl ring (C31-C36). Interestingly, two other phenyl rings (C37C42 and C43-C48) are almost orthogonal to the best plane of the porphyrin macrocycle (the corresponding torsion angles are 85.2 and 80.2°, respectively). Instead; the compensation for it seems to be made by pushing the - C F groups away from these phenyl groups (C37-C42 and 3  C43-C48). SmaU C4-C3-R (R=C22)  and C11-C12-R (R=C23)  angles (see  Table 2-13)  are  indications of the interaction between the phenyl groups (C37-C42 and C43-C48) and the - C F  3  groups that eventually forces the two phenyl rings (C25-C30 and C31 and C36) to rotate. This structural relationship is clearly shown in Figure 2-33(b), which is a part of the crystal structure of Zn(TPP(CF ) ) (48b) 3  4  projected from the direction indicated by the arrow in the stick model of  the top view of the molecule (Figure 2-33(a)). The steric interaction between the phenyl (C43C48) and - C F (F1-F3) determines the orientation of the - C F so that no F of F1-F3 is pointing 3  3  at the face of the phenyl ring. This orientation makes the F3 point at the adjacent - C F (F4-F6), 3  which orients so that F3 points between F4 and F5. Similarly the orientation of the - C F (F4-F6) 3  shifts the position of the phenyl ring (C25-C30) to minimize the steric interaction. In addition, the negative interactions between the 7t-cloud of the phenyl rings and the - C F groups may be 3  the driving force for the severe distortion of the macrocycle. A n electrostatic repulsion between the electronegative fluorine and the 7t-electrons is k n o w n .  2 2 2  The distance from the center  168  F i g u r e 2-33.  Orientations of phenyl and  CF  3  groups in  a projection of a part of the crystal structure, 48b from the direction indicated by the arrow.  48b. (b) shows  shown by stick model (a),  169  of the carbon atom to the plane of the adjacent phenyl ring would be approximately 3 A, if it were not for steric interactions. Since the half thickness of benzene is 1.85 A  1  2  3  and the vdW  radius of —CF is at least 2.2 A ^ " , a strong electronic repulsion between these two groups is 2  3  expected. The average torsion angles made by the C 72.9° in Zn(TPPBr ) (45b) 4  o r t h o  -C -C „„-C are 68.4, 78.2, 76.8, and ph  OT  a  and 75.9, 67.6, 71.5, and 71.3° in Zn(TPP(CH ) ) (59b) 3  4  and none of  the phenyl groups in 4 5 b and 5 9 b is severely twisted. Figure 2-34(b) shows the orientations of phenyl and C H groups featured in a part of the crystal structure of 59b. 3  There is no such strong  interaction between the phenyl and C H groups as that observed in Zn(TPP(CF ) ) ( 4 8 b ) . 3  3  4  (4) Orientation of the axial ligand A n interesting feature of the crystal structure of 48b-(EtOH) is the orientation of E t O H 3  molecules to the macrocycle distortion. A s shown in Figure 2-30-45b and Figure 2-30-59b, in 45b-(MeOH)-(DMF) and 59b-fTHF)j.-(CHCl3) axial ligands are coordinated to Zn(II) on top 6  a4  of the bow-like shape created along the direction of antipodal P-substitution (Scheme 2-11(a)). O n the other hand, in 48b-(EtOH) (Figure 2-30-48b) an ethanol is coordinated to Zn(II) in the 3  bow-like shape along the direction with - C F groups (Scheme 2-11 (b)). Interestingly, as shown in 3  Figure 2-30-48b, the axial ethanol is hydrogen bonded to the second ethanol (HI whose methylene hydrogen (H32) has a non-bonding contact with F9 (H32 third  ethanol  ethanol (03  (not shown  in the figure) is also  0 2 (1.90 A)),  F9 (2.71 A)). The  hydrogen-bonded  to the second  H31 (2.03 A), where 0 3 is the oxygen atom in the third ethanol and H31 is  hydroxyl hydrogen of the second ethanol). There were also many other H  F nonbonding  contacts within 3 A between solvent ethanols, P-pyrrolic hydrogen, or phenyl ring hydrogen and  170  F i g u r e 2-34.  Orientations of phenyl and C H  3  a projection of a part of the crystal structure, 59b from the direction indicated by the arrow.  groups in  59b. (b) shows  shown by stick model (a),  171  R=Br, C H L=MeOH, T H F  =porphyrin macrocycle  3  L  (a)  (b)  S c h e m e 2-11.  Schematic representations of macrocycle distortion and axial coordination in (a)Zn(TPPBr)(45b)• (MeOH) and Zn(TPP(CH))(59b)-(THF) and in (b) Zn(rPP(CF ) ) (48b) • (EtOH). 3 4  4  3  -CF  4  moieties across the different porphyrin units. Intermolecular c _ p 5+  3  dipole interactions or C-H—F-C  hydrogen bonding is known. 26 1  5  d "C-H 5  a  n  8 +  bond  Unfortunately, these  non-bonded contacts are so complicated in this porphyrin system that they cannot be pictured in an appropriate way.  In summary, crystal structure analysis of three zinc complexes of P-teteasubstitued mesotetraphenylporphyrins showed elongated macrocycle cavities due to the substituents on the pyrrolic P-positions of antipodal pyrroles. Elongation of the macrocycle was reflected in different Z n - N distances (or core sizes) in the directions of P-substituted pyrroles and of nonsubstituted pyrroles. The Cp-Cp bonds in the P-substituted direction can also be stretched due to the strong election-withdrawing and/or steric effect of the P-substituents. The structure analysis also revealed slightly distorted macrocycles of Zn(TPPBr ) (45b) 4  and Zn(TPP(CH ) ) (59b) 3  4  and  very distorted macrocycle of Zn(TPP(CF ) ) ( 4 8 b ) . These observations support the results 3  4  obtained in UV-visible spectroscopy and electrochemistry. Electron-deficiency is reflected on the shortening of Z n - O distances in 45b-(MeOH) and 48b-(EtOH). A n interesting result to be noted  172  is that axial ethanol as well as one of the two solvated ethanols are found in a pocket created by C F groups and the macrocycle distortion. This could be due to the high affinity of - C F moieties 3  3  to the hydrocarbon moieties for ethanol and may be an advantageous property for hydrocarbon oxidation using the Fe(III) complex of this porphyrin as a catalyst.  5. Spectrophotometric titration In  Chapter II, section B.3.,  the  electron-deficiency  of fi-tnQuoiomethyl-meso-  tetraphenylporphyrins was evaluated by the analysis of redox potentials measured by cyclic voltammetry.  In  section B.Za.  describing  (3-tos(trifluoromethyl)porphyrin H T P P ( C F ) 2  3  3  NMR  spectroscopy  experiments  of  ( 4 7 a ) , it was shown that exchange of N H protons  of the porphyrins with the proton of residual water easily occurs. This phenomenon may be related to the lower pK, value for the first deprotonation of the free-base porphyrin compared to non-electron-deficient porphyrins such as H T P P (2a) 2  (Figure 1-8, p . l l ) . Given this, it became  essential to estimate the piC, of P-trifluoromethylporphyrins. In the first part of this section, spectrophotometric  titrations  of  tetraphenylporphyrin (H TPP(CF ) 2  3  4  the  free-base  p-tetrakis (trifluoromethyl) -meso-  of  ( 4 8 a ) ) with D B U and E t N in C H C 1 are shown. In the 3  second part, spectrophotometric titrations of Co(TPP(CF ) ) (48e) 3  4  2  2  with pyridine (Py) and  imidazole (lm) are shown. There are a few reports of determination of Py and l m binding constants of Co(II) porphyrins. 177-180 These include some electron-deficient porphyrins. Comparison of the binding constants with other electron-deficient porphyrin systems was allowed by analysis of the titrations using 48e.  Thus, this section provides additional information  regarding the electron-deficiency of P-tetralds^fluoromethy^-OTWO-tettaphenylporphyrin.  173  a. Titration of 48a with strong organic bases in  CH C/ 2  2  (1) Titration with DBU Figure 2-35 shows the results of the spectrophotometric titration of 48a with D B U in CH C1 . Figure 2-35(a) shows an isosbestic spectral change for the first deprotonation. The 2  2  arrows indicate the direction of the change of the absorption peaks. The color of the solution changed from golden-yellow for the free-base to weak orange for the first deprotonated species. This colorimetric change stopped at [DBU] = 4.5 x 10" M. After the first deprotonation, the 2  second deprotonation was attempted using neat D B U (Figure 2-35 (b)). The further colormetric change was observed, but the spectral change did not stop for the second end point. Assuming that the spectrum at [DBU] = 4.5 - 5.4 x 10  2  M is that of the porphyrin monoanion, the pK  difference between H P (P stands for porphyrin dianion) and DBUH (protonated D B U ) was +  2  determined (see Experimental section in Chapter TV). The results were analyzed based on the absorbance change at 463 and 513 nm (s™' =9.34 x 10 , s™~ =3.22x 10 , S ^ J =8.78 x 10 , and 4  e  M3  =  4  3  3.72 x 10 M "'xm"') ). The logarithmic analysis of the first colorimetric change gave a 4  straight line with a slope of 1.1 and the intercept of 2.9 as the pK value for the reaction, H P + 2  D B U <^ H F + D B U H  (Figure 2-36). The p X i s indeed the difference between the pK\. (pK,  +  nv  of H TPP(CF ) ) and p K 2  3  4  (pK, of D B U ) (see Chapter IV, Section C , Spectrophotometric  D B U  titrations.); pK = ApiC, = p.K p - p X H2  24223,224  a  n  d  D B U  . The pK^ of D B U in M e C N was determined as  ^ in H 0 was estimated as 1 4 . 2  2 2 3  Unfortunately, the pK, of D B U in C H C 1 is 2  2  not known. Thus, we can only compare the acidity of porphyrins by using D B U as an anchor. Woller and DiMagno determined the pi<Q difference (ApiCj between electron-deficient porphyrins H T P P F (12a), H T P F P P F (13a) (Figure 1-8, p . l l ) and D B U in C H C 1 by the same 2  8  2  8  2  2  method and found that the N H in 12a and 13a were less acidic than protonated D B U by 3.9 and  300  400  500  600  700  800  900  1000  Wavelength (nm) Figure 2-35. UV-visible spectral change in titration of H T P P ( C F ) (48a) 2  D B U in C H C 1 . [48a] 2  2  3  4  with  = 1.24 x 10" M . (a) The first deprotonation at [DBU] = 5  0 - 5.4 x 1 0 M . N o spectral change between 4.5 x 10" and 5.4 x 10" M . _2  2  (b) The spectral change at [DBU] = 5.4 x 10" ~ 1.5 M . 2  2  1 Log([H P]/[HP-]) = 1.1 x log ( p B U H ] / [ D B U ] ) + 2.9 +  2  -2 H -4  1  1  -3  -2  1  :  -1  log [H P]/[HP-] 2  F i g u r e 2-36.  Logarithmic analysis of the spectral data for the addition of D B U to  H T P P ( C F ) (48a) 2  of 48a  3  in C H C 1 . pK = pK -pK ;  4  2  2  and D B U H , respectively. +  H2V  mv  pK  mv  and pK  Dm  are pK  a  176  units respectively and 12a was at least 1000 times more acidic than H T P P (2a)  0.2  2  2a > 19).36 The ApK, of 2.9 for 48a  (pK, for  proves that this porphyrin is indeed an electron-deficient  porphyrin.  (2) Titration with Et N 3  A similar titration was performed on 48a in C H C 1 with taethylamine. Figure 2-37 shows 2  2  the UV-visible spectral change for the titration. The spectral change occurred isobestically but in a different way from the titration with D B U . N o further spectral change occurred after [taethylamine] == 1.43 x 10 (s = 7.45 x 10 M 4  _ 1  1  M . The final spectrum has only one broad band at 420 nm  cm ). The color of the final compound was orange. This orange color _1  slowly fades away in C H C 1 solution at room temperature. When 6 x l O ^ M of H T P P ( C F ) 2  2  2  3  4  was treated with 0.29 M of taethylamine in CH C1 , the initial peak intensity at 420 nm of the 2  2  orange compound dropped to 40% in a few days at room temperature and no other new peaks were observed. The UV-visible spectrum of the orange compound was the same as that in Figure 2-4; the porphyrin is presumably reduced by E t N . 3  b. Titration of Co(TPP(CF ) ) } 4  Binding  constants  Co(TPP(CF ) ) (48e) 3  4  (48e) with pyridine and imidazole for  pyridine (Py)  and  imidazole (Im)  coordination  to  were also measured in C H C 1 by spectrophotometric titration. 2  2  The UV-visible spectra given in Figure 2-38 show the change for the first step of pyridine addition to 48e.  The spectral change showed six isobestic points and is very similar to the change  for the first pyridine coordination to Co(TPP(CN) ) in C H C 1 . ^ 4  2  2  9  The second coordination was  very slow and thus titration was not possible, though spectral changes occurred with isobestic points.  This  result  is  shown  in  Figure 2-39.  When  40,000  eq.  of  pyridine was  0.7  350  450  550  650  750  850  950  Wavelength (nm)  F i g u r e 2-37. UV-visible spectral change in titration of H T P P ( C F ) ( 4 8 a ) with E t N in C H C1 . [48a] = 5.74 g 10 " M . [Et N] = 0 - 4.30 x 10 M . 2  6  3  2  2  3 4  4  3  178  0.0 H 350  1  400  1  1  1  450  500  550  Wavelength (nm)  F i g u r e 2-38.  Titration o f C o C T P P ( C F ) ) (48e)(8.60 x 10 ~ M ) i n C H C l w i t h pyridine 6  3  4  2  2  at 25.0 ° C : spectral change at (a) 350 - 850 n m and (b) the Soret b a n d region during the transition between 4- and 5-coordinate cobalt, [Py] =0 - 2.76 x 10 " M . 3  350  450  550  650  750  850  Wavelength (nm)  F i g u r e 2-39. Spectral changes in the pyridine addition to Co(TPP(CF ) )- (Py) 3  (48e-  4  (Py)) (8.60 x 10 " M) in C H C 1 at 25.0 ° C . [Py] = 2.76 x 10 " - 3.40 x 10 6  3  2  2  4  180  added to the Co (II) porphyrin, a slow change of the spectrum with time was noticeable. It took about 15 days at 25 °C for the reaction to reach the equilibrium. Similarly, a slow second ligand addition reaction was observed using imidazole at 25 °C. For Co(TPP(CN) ), CofTPPFg), and 4  Co(TPFPPF ) such a slow reaction for the second ligand addition was not reported and the 8  binding constants (X, and K^) were given.179,180 -p^e reason for the slow reaction might be the sterically very crowded porphyrin peripheral of Co(TPP(CF ) ) 3  4  ( 4 8 e ) . It was shown in the  analysis of the crystal structure of Zn(TPP(CF ) ) (48b) that macrocycle distortion occurs due to 3  4  the interaction between the phenyl rings and - C F groups. Coordination of first Py (or lm) to 3  four  coordinate  4 8 e  may result  in a similar  structure  that  was observed for  Zn(TPP(CF ) )-(EtOH) (48b-(EtOH)) (Figure 2-30-48b) with Co(II) deviated from the N 3  4  3  3  4  plane. As discussed in section B.4., the severely saddle-distorted macrocycle of 48b-(EtOH) is a necessary structure to minimize the interaction between the phenyl and —C F  3  groups. The  second axial coordination to the five-coordinate Co(II) complex would have to by necessity move the Co(II) into the centroid of the four pyrrolic nitrogens. The two axial nitrogens and the change from the five-coordinate to the six-coordinate complex may also require rearrangement of the peripheral substituents. Since the steric interaction among the peripheral substituents is severe  in  the  P-tetraltis(trifluoromethyl)-wwo-tetiaphenylporphyrin  ligand  (chapter II,  section B.4.), fast change from the five- to six-coordinate complex may be encumbered. The reason that the logJ<C for Co(T((?-OCH )PP) (43) 1^8 2  3  w  a  s  n  o  t  g i n may be a too weak binding of v e  the second ligand. Thus in order to observe binding of the second ligand, an electron-deficient and planar macrocycle ligand is necessary.  I  F i g u r e 2-40.  181  Logarithmic analysis of the spectral data for the addition of  pyridine to Co(TPP(CF))(48e) in C H C 1 . The pyridine addition step was 34  2  2  monitored at 440 nm. A , A , and Ay are absorbances without pyridine, 0  at each titration point, and at the final point, respectively.  182  Logarithmic analysis (Hill's plot) - of the spectrophotometric data for the first pyridine 22  5  addition is shown in Figure 2-40. The analysis gave a binding constant of log iC, = 4.2. A similar experiment with imidazole gave log iC, = 7.5. These results are listed in Table 2-15 with reported  T a b l e 2-15. Binding constants of Co(II) porphyrins for base binding in in CH^CLj. Porphyrin Co(rPP(CF ) ) (48e) 3  4  CoCl>-OCH )PP) 3  (43)  (34c)  Co(TPP(CN) ) 4  CofTPPFg) (12h) Co(TPFPPF ) (14h) 8  a  Base Py Im  log K 4.2 7.5  Py Im 1-Melm Py Py Py 1-Melm  2.68 3.15 3.37 4.2 4.3 5.9 6.8  log K  x  b  b  Reference  2  a  -  a  -  158 158 158 179 180 180 180  -  -0.35 -0.08 1.03 1.76  This work. 1-Memylimidazole. b  values of other Co(II) porphyrins. Porphyrin 48e binding of Py to those of 34c  has a similar binding constant for the first  and 12h (see p.62 for the structures) and the value for 48e is larger  than that of 43. Thus, the result proves the electron-deficiency of the P-tetrakis(trifluoromethyl)OTWO-tetraphenylporphyrin ligand. The increment from the log and 14h  for Py to that for Im of 48e,  43,  correlates with basicity of the ligands (pJQ values; Py: 5.22, Im: 6.65, and l-Melm:  7.06)158 hut the increase for 48e  seems to be large compared to those for 43 and 14h.  A  rationale for this phenomenon is that the smaller axial base (Im) is preferable for binding to sterically hindered  48e.  6. Summary P-Trifluoromethylporphyrins H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  3  H TPP(CF ) 2  3  3  ( 4 7 a ) ,  H TPP(CF ) 2  3  4  ( 4 8 a ) ,  showed bacteriocHorin-like UV-visible spectra that suggest fixed  187t-electron pathways of these porphyrins (section B./.). The H N M R experiments using J  47a  183  suggested that the porphyrin preferably takes the fixed 187t-electron pathway (section B.2). The analysis  of the H O M O - L U M O  gaps of P-ttifluoromethylporphyrins obtained by cyclic  voltammetry also suggested that the  tautomerism of the  two  electronic  pathways  of  /^jtf-tettaphenylporphyrin is shifted into one, like that of bacteriochlorin, due to the strong electron-withdrawing effect of the —CF groups (section B.J). 3  The  steric effect of the —CF groups was shown by the analysis of an X-ray crystal 3  structure of Zn(TPP(CF ) ) (48b) 3  4  (section B.4). The estimated van der Waals radius of - C F  3  from the crystallographic data is 2.7 A and the steric interaction between the meso phenyl groups and the bulky —CF groups seems to be the driving force of a severe saddle distortion of the 3  macrocycle. The steric effect of the —CF groups in the P-tetealris(tofluoromediyl)porphyrin 3  ligand possibly correlates with the large red-shifts and broadening of the UV-visible absorption bands, the unusual ' H N M R chemical shift for the pyrrolic P-protons, the non-linear increase of the first oxidation potentials, and the slow base binding to the Co(II) complex.  Comparison of the reduction potentials, the pK value for the first deprotonation of the a  N H protons, and the binding constant of Py and l m to Co(TPP(CF ) ) (48e) 3  4  with those of other  electron-deficient porphyrin systems proved that the P-tettalds(tjifluoromethyl)porphyrin ligand is  electron-deficient.  The  Fe(TPP(CF ) (CF CF )Cl (52c) 3  3  2  3  Fe(II/III)  reduction potentials  of  Fe(TPP(CF ) )Cl (481) 3  4  were tuned in the ideal range for an oxidation catalyst; between  those of the second and the third generation porphyrin catalysts such as Fe(TPFPP)Cl (4d) Fe(TPFPPBr )Cl (8d). 8  and  Thus, the catalytic activities of 48f  and 52c  assess the usefulness of these complexes as oxidation catalysts.  and  were investigated in order to  184  C. C a t a l y t i co x i d a t i o n of c y c o lh e x a n e and c y c o lh e x e n e As reviewed in the first chapter, some electron-deficiency is necessary to improve the catalytic activity and the robustness of metalloporphyrins. In order to investigate the usefulness of the Fe(III) complexes of P-oifluoromethyl-OTMo-tetj:aphenylporphyrins Fe(TPP(CF ) )Cl 3  and Fe(TPP(CF3)3(CF CF )Cl (52c) 2  3  4  (481)  as oxidation catalysts, hydroxylation of cyclohexane and  epoxidation of cyclohexene in C H C 1 2  2  was examined. As discussed briefly in Chapter I,  section A . Z d , detailed reaction conditions for catalytic oxidation in the studies of porphyrin catalysts are diverse. Although we have to keep this point in mind, the performance of 48f and 52c  was compared with that of one of the best porphyrin catalysts F e ^ D C P P C k j C l (10d)226  (third generation porphyrin catalyst) under the same reaction conditions.  In a catalytic oxidation of cyclohexane, to a C H C 1 solution containing 1 eq. of the 2  2  porphyrin catalyst and 5,000 eq. of cyclohexane, 200 eq. of PhIO were added during the first 1 h. The reaction was performed in a vial at 24 °C for 4 h. The solutions of 48f and 52c  are green but  both solutions turned orange instantiy when the first 50 eq. of PhIO was added and the orange color gradually faded away during the reaction. The solution of 45e  was greenish yellow at the  beginning of the reaction and it was bleached gradually too. The solution containing O ld  was  green and the color was almost maintained during the reaction. After the reaction, the liquid phase of the reaction mixture was analyzed by gas chromatography. The results are summarized in Table 2-16. Since the amount of substrate used is a large excess, normally the yield of the product is given based on consumed oxidant; (peak area of cyclohexanoi)/(peak area of Phi) x 100 is reported in Table 2-16.  185 T a b l e 2-16. Oxidation of cyclohexane and cyclohexene using Fe(III) porphyrins and iodosylbenzene in C H C l . 2  a  2  .  cyclohexanol Yield (%)  y S t  b  cyclohexene oxide  turnover  1  Yield (%)  turnover'  b  Fe(TPP(CF ) )Cl (481)  7  5  62  77  Fe(TPP(CF ) (CF CF ))Cl (52c)  9  6  61  61  5  4  68  82  44  86  89  109  3  3  4  3  2  3  Fe(TPPBr )Cl (45e) 4  Fe(TDCPPCl )Cl (O l d) 8  Reaction conditions: CH C1 = 500 pL, catalyst = 1x10^ mmol, cyclohexane = 5 x 10 mmol, cyclohexene = 1 mmol, PhIO = 2 x 10 ~ mmol. For hydroxylation; temp. = 24 °C, t = 4 h. For epoxidation; temp. = 30 °C, t = 2 h. Based on PhIO consumed . Product (mmol)/catalyst (mmol). a  2  2  _ 1  2  b  c  Although we cannot direcdy compare these data with the literature values such as those shown  in  Chapter I,  there  was  a  clear  p-trifluoromethylporphyrins Fe(TPP(CF ) )Cl (48f) 3  4  difference  between  the  yields  and Fe(TPP(CF ) (CF CF ))Cl (52c) 3  3  2  3  with  and the  third generation catalyst, Fe(TDCPPCl )Cl ( l O d ) . Fe(III) porphyrins 48f and 52c are not good 8  oxidation catalysts at least under these conditions. The Fe(III) complex 45e was also found to be ineffective for hydroxylation of cyclohexane. Bleaching of the solutions containing 45e,  48f,  and  52c implies that these porphyrins may be decomposing during the reaction.  Epoxidation of cyclohexene was performed under the same conditions except for the amount of the substrate. The yields of the epoxide from cyclohexene were much higher than those for hydroxylation but the result shows that catalysts 48f P-halogenated porphyrins. The solutions of 48f  and 52c  and 52c  are not as effective as  were not completely bleached during  the reactions but the color of the porphyrins faded away gradually.  Since a supply of 48f and 52c was not enough, thorough examination of hydroxylation and epoxidation could not be performed. However, the preliminary tests regarding catalytic oxidation  186  showed the instability and the ineffectiveness of 48f porphyrin catalysts lOd.  and 52c  compared to one of the best  Potential reasons for these results are:  The first oxidation potentials (ring oxidation) of 48f and 52c are about the same as that of Fe(TPP)Cl (2d)  (see Table 2-12). Oxidation of 48f and 52c is as easy as that of 2d.  The macrocycles are destabilized by severe distortion caused by the steric or the electronic interaction between the peripheral substituents.  Thus, the  electron-  withdrawing effect of - C F groups does not contribute to improve robustness of the 3  macrocycle.  Although Fe(III) porphyrins 48f  and 52c  have four bulky perfluoroalkyl groups but  there are still (3-hydrogens and twenty phenyl-hydrogens. Thus, more protection of the macrocycle may be required for robustness. As observed in the crystal structure of Z n T P P (CF ) ( 4 8 b ) , meso-xphenyl rings are extremely tilted by the steric or the 3  4  electronic interactions with - C F groups. This may facilitate the formation of the 3  p,-oxo dimer. In fact, the u-oxo dimer (61) is easily formed from 48f  (Scheme 2-8,  p.93).  Ligands 48 and 52 presumably take a bacteriochlorin-type electronic structure. The macrocycles should be redox sensitive due to the small H O M O - L U M O gap; the low first oxidation and the high first reduction potentials. Thus, this may trigger a decomposition of the macrocycles.  As discussed in this Chapter, P-tafluoromethylporphyrins are electron-deficient and introduction of the - C F groups on the pyrrolic P-positions of antipodal pyrroles leads to the 3  187 unusual electronic properties and the structure of the macrocycle. However, this seems to be not advantageous for an activity as oxidation catalysts.  188  C H A P T E R III  Conclusions and Future Work  A . Conclusions In these studies towards the synthesis of novel electron-deficient porphyrins, based on the structure of ^jo-tetraphenylporphyrin, - C F  3  groups were introduced onto the  pyrrolic  P-positions of the macrocycle using P-bromo-^wo-tetraphenylporphyrins and the agent in-situ generated C F C u . Trifluoromethylation at the pyrrolic P-position of ^.ro-tettaphenylporphyrin 3  was difficult due to the steric bulkiness of the —CF group. Therefore, the maximum number of 3  —CF groups added to the porphyrin was four. 3  Partially introduced —CF groups at the antipodal pyrrolic P-positions not only made the 3  macrocycle electron-deficient but also directed the 187t-electron pathway of the porphyrin macrocycle to take one similar to that of bacteriochlorin. The unique electronic structure of the P-tofluoromethylporphyrins resulted in red-shifted bacteriochlorin-like UV-visible spectra. The unique electronic pathway in the novel porphyrins was proved by the locked positions of N - H protons determined by ' H N M R spectroscopy.  The analysis of the redox potentials  of  P-tofluoromethylporphyrins showed a progressive decrease of the H O M O - L U M O gap along with the antipodal trifluoromethylation. This was also an indication of the bacteriochlorin-like distorted 187t-electronic pathway. Redox potentials also enabled approximate comparison of the electron-deficiency  of P-trifluoromethylporphyrins with other electron-deficient  porphyrin  systems. However, the comparison has to be done carefully because in the conclusion of this work, the electronic structure of the novel p-teifluoromethylporphyrins is different and thereby  189  the redox potentials may change. The electron-deficiency of p-tettalds(mfluoromethyl)porphyrin was evaluated to be the same as the reported electron-deficient porphyrins such as P-octafluoro/wwo-tettaphenylporphyrtn (TPPFg) or P-teteacycano-/W£ro-teteaphenylporphyrin (TPP(CN) ) by 4  the determination of the pXa and the axial base binding constants to Co(II) porphyrin.  The - C F groups on the pyrrolic P-positions also exhibited a large impact on the structure 3  of the macrocycle as a result of steric interactions between - C F and - C F groups and between 3  -CF  3  and  phenyl  groups.  The  macrocycle  of  3  P-tetrakis (trifluoromethyl) -meso-  tetraphenylporphyrin is distorted into a saddle shape. The van der Waals radius of the - C F  3  group obtained from HyperChem and the X-ray crystal analysis is 2.7 —2.8 A, which is large enough for steric interaction between the substituents to lead to such macrocycle distortion.  Fe(III) complexes of P-trifluoromethylporphyrins showed a well-tuned Fe(III/Il) redox couple which was comparable to those of good porphyrin catalysts such as the second and the third generation porphyrin catalysts.  However, it was  found that Fe(III) complexes of  P-tofluoromethylporphyrins were not superior catalysts to the third generation porphyrin catalyst Fe(TDCPPCl )Cl in oxidation of cyclohexane and cyclohexene. Stability of the catalysts seems to 8  be the problem. The unique electronic structure of the P-trifluoromethylporphyrins could be disadvantageous for a stable macrocycle system.  B. F u t u r ew o r k Studies of redox properties of the macrocycle in a series of porphyrins bearing strong electron-withdrawing groups such as —CN or —NO have been reported37>161 but the detailed z  electronic structures and spectroscopic properties have not been reported in the literature.  190  Although redox properties of some series of P-brominated zwo-tettaphenylporphyrins have been extensively studied by Kadish et « / , 1 6 2 - 1 6 4  a  unique electronic structure of the macrocycle like  the system observed in this work has not emerged in the series of brominated porphyrins probably because the —Br group is mildly electron-withdrawing. One way to continue these investigations regarding the electronic structures of the macrocycle may be to extend the series of P-trifluoromethyl-^j'o-tetophenylporphyrins. This would allow us to see the change in spectroscopic and electrochemical data through which we could determine the electronic structure ofthe macrocycle. However, the synthesis of highly P-trifluoromethylated porphyrins is challenging and may not be productive because P-pyrrolic positions are not suitable for smooth introduction of —CF groups. In addition, separation becomes more difficult as the number of 3  perfluoroalkyl moieties increases. Thus, the details of effects of extremely strong electronwithdrawing substituents on the electronic structure of the macrocycle may be investigated by P-cyano or p-nitroporphyrins. P-Nitration of a ^wo-tetraarylporphyrin is fully controllable by the method  recently  devised  by  Palacio et affl  and  allows  access  to  P-mono-  to  P-octanitroporphyrins.  Although trifluoromethylation on the pyrrolic P-position of the macrocycle is difficult, a different porphyrin system may be synthesized to achieve high-performance porphyrin catalysts. A potential porphyrin candidate is shown in Scheme 3-1. The first measure Groves et al. took to achieve some improvement from Fe(TPP)Cl (Figure 1 -8) was to introduce the steric bulk on the periphery  of  the  macrocycle  and Fe(TMP)Cl (Figure 1-8)  appeared.98  This  porphyrin,  (Fe(TMP)Cl), is not likely to be a good catalyst for oxidations. The meso- and pyrrolic  191  P-positions are protected by the bulky mesityl groups but methyl groups in the mesityl groups are exposed to the exterior. These are problematic for robustness of the catalyst. If a metal complex of w<?.ro-tetealds(2,6-dibromophenyl)porphyrin (65) and C F C u are used, T M P 3  analogous OT^o-tettakis(2,6-bis(tofluorometiiyl)phenyl)porphyrin (66)(Scheme 3-1 (a))  may be  obtained. The synthesis of 66a was attempted by Lindsey et al. by condensation of pyrrole and 2,6-bis(tofluoromediyl)benzaldehyde67  but was unsuccessful, presumably due to the steric  hindrance of the two —CF groups on the benzaldehyde, preventing cyclization with pyrrole. In 3  the porphyrin, the o^o-positions  of the meso-phenyl groups are not hindered and thus  introduction of the —CF groups there may not be as difficult as that of the pyrrolic p-positions. 3  A geometry optimized molecular structure of 66a by HyperChem (Scheme 3-1 (a) and (b)) shows a planar macrocycle and four orthogonal meso-aryl groups to the macrocycle. The —CF groups 3  are more stable and bulkier than the — C H groups (Chapter I, section B.J.b). Thus, it is expected 3  that the —CF groups may protect the macrocycle effectively. The distance from the macrocycle 3  to the edge of the ortho-CP^ groups (Scheme 3-1 (c)) is approximately 5 A. This distance also suggests that formation of the  p-oxo  dimer would be unlikely. Finally the meso-2,6-  bis(trifluoromethyl)phenyl groups are electron-withdrawing and they can keep the macrocycle electron-deficient. One problem for this future work may lie in the synthesis of porphyrin 65, which  is  a  known  compound  2,6-dibromobenzaldehyde.67  synthesized  by  condensation  of  pyrrole  and  However, 2,6-dibromobenzaldehyde is not manufactured right  now. Thus, we need to synthesize 2,6-dibromobenzaldehyde in order to obtain porphyrin 65.  Attempts towards the synthesis of P-octolds(ttifluoromethyl)-^j"o-arylporphyrins may not be an appropriate direction for improvement of the catalytic activity of porphyrin catalysts. The  S c h e m e 3-1. wwo-Tettakis(2,6-bis(rjifluoromemyl)phenyl)porphyrin (a) A possible synthetic route for 66.  (b) A computer m o d e l o f  (c) A side view o f the computer m o d e l .  1 8 9  66a.  (66).  193  eight —CF groups on the pyrrolic p-positions promise a high electron-deficiency of the 3  macrocycle, but too much electronegativity may lead to stable Mn(II) or Fe(II) porphyrins, which are inactive as monooxygenase systems, as shown by Grinstaff ^ « / . ( F e ( I I ) ( T P F P P B r ) ) 0 7 1  8  BartoH eral ( M n ^ t T D C P P f N O ^ ) .  4 7  a n c  j  Therefore, super electron-deficiency is not an ultimate  solution for a perfect cyctochrome P-450 mimic.  The ultimate goal for P-450 model compounds may be to let metalloporphyrins utilize molecular 0  2  (or air) as a source of oxidant to form the oxo Fe(IV) porphyrin 7t-cation radical,  the key intermediate in the P-450 catalytic cycle. ^ ^ As reviewed in Chapter I, two electrons 2  4  and two protons are required in order to form the intermediate from Fe(III) porphyrin and 0 and to reduce one of the oxygen atoms of 0 only 0  2  2  2  to water. Thus, mimicking the P-450 cycle with  and synthetic Fe(III) seems very difficult. However, the oxo Fe(TV) porphyrin 7i-cation  radical can be also formed via the shunt path (see Figure 1-5) using an oxygen atom transfer reagent. Although there are variety of " O " transfer reagents such as N a O C l , PhIO, peroxides, and peroxy acids, the use of these reagents generates by-products (NaCl, Phi, etc.). A n exception is hydrogen peroxide. Although hydrogen peroxide is more costiy than molecular 0 , it is a 2  competitive source of oxygen atoms with molecular 0 . since it is a clean and environmentally 2  friendly o x i d a n t .  227  A n ideal reaction of Fe(III) porphyrin and hydrogen peroxide for catalytic  oxidations is shown in Scheme 3-2(a) (Path A),  where heterolytic O - O bond cleavage of  Fe(III)-0-0-H occurs to form the oxo Fe(IV) porphyrin 7T-cation radical. For this type of cleavage, polarization of the O - O bond is necessary.53 As shown in Scheme 3-2(b), the - C F  3  groups on the ortho-positions of the meso-aryl groups might help polarization of the O - O bond  194  via the hydrogen bonding. Formation of p-peroxoclimer (Scheme 3-2(a), Path B) should be ruled out due to the bulky —CF groups. 3  The ortho-CP\ groups might play the following important roles in catalytic oxidations; (1) protection of the macrocycle by their steric and electron-withdrawing effects, (2) formation oxo Fe(TV) porphyrin Tt-cation radical by the use of H O via an intramolecular interaction, and 2  z  (3)activation of the active intermediate by electron-withdrawing effects. Therefore, investigation of metal (such as Fe(III) or Mn(III)) complexes of porphyrin 66 may provide new insights for the development of cyctochrome P-450 model compounds. M  +  H  O  X (a)  Fe(lll)  H,0 2^2  Fe(lll)  Path B  Path .4  Fe(IV)  •H,0  PFe(lll)  porphyrin dianion  O  x = anion (Cl", OH", etc.)  2x  Fe(IV)  PFe(lll):  (b)  Scheme 3-2.  -FUO  \ _  Formation of oxo Fe(IV) porphyrin 7t-cation radical from Fe(III)  porphyrin and hydrogen peroxide, (a) Reaction pathways, (b) Mode of activation of the O - O bond.  195  C H A P T E R IV  Experimental  A . Chemicals All chemicals for synthesis were purchased from Sigma-Aldrich fine chemicals, Across Chemicals,  or  Fisher  Scientific.  If  necessary,  chemicals  were  purified  by  published  procedures. ^ Deuterated solvents for N M R measurements were purchased from Cambridge 22  Isotope Laboratories or Aldrich. Chlorinated solvents were filtered using N-alurnina (activity I) to remove trace acid (HC1 or DC1). Column chromatography was performed using 70 - 230 or 230 - 400 mesh silica gel (Merck). Analytical thin-layer chromatography was performed using pre-coated silica gel aluminum plates which contains a fluorescent indicator (GF 254 Merck).  B . Instrumentation UV-visible spectra were recorded on a Varian Cary 50 scan UV-visible spectrophotometer or a Hewlett-Packard 8452A diode array spectrophotometer. N M R spectra were recorded on Bruker AC-200, WH-400, or Avance 300 spectrometers. Cyclic voltammetry measurements were performed on a Pine Instrument Company bipotentiostat model A F C B P 1 and Pine Chem Sweep Voltammetry software for Windows v. 2.00. The cyclic voltammetric experiments were performed using an electrochemical cell as shown in Figure 4 - 1 .  2 2 9  X-ray crystallographic data  were collected on a Rigaku/ADSC C C D . A Hewlett-Packard G C HP-17 was used to detect oxidation products. This G C utilizes a phenyl methyl silicone (50 % crosslinked, 25 m x 0.32 m m x 0.26 um (length x tubing inner diameter x film thickness)) capillary column, and a flame ionization detector, and helium was used as a carrier gas.  90°  F i g u r e 4-1. Electrochemical cell and electrodes (a. Pt working electrode, b. A g reference electrode, c. Pt counter electrode).  197  C . Procedures Cyclic voltammetry. C H C 1 and P h C N were distilled and degassed by three cycles of the 2  2  freeze-pump-thaw method and dried over activated molecular sieves 4A. A sample solution for a measurement was prepared by the following procedure. A r was introduced from gas inlet E (see Figure 4-1 for designations A - E and a - c). The electrochemical cell was dried using a heat gun. Electrodes a, b, C were also dried using a heat gun and placed in A, B, C of the cell, respectively, so that the electrodes did not contact each other and were then cooled under a slow A r stream. For a typical measurement, porphyrin typically (0.015 - 0.03 mmol), and T B A P F (0.3 mmol) 6  were weighed and transferred to the cell through D. Dry solvent (3 mL) was then introduced into the cell through D. The solution was bubbled with A r for a few minutes, and then D was closed with a glass stopper. The connections at A, B, C, and D were secured with parafilm. A n A r balloon was put on E and the stopcock was then opened. Porphyrin was dissolved completely using a sonicator. The cell was connected to the potentiostat and voltammograms were recorded without stirring the solution. In order to standardize the potentials, ferrocene (0.005 mmol) was added to the solution from D. Voltammograms were recorded again under the same conditions. Addition of ferrocene did not affect the redox potentials of porphyrins.  Spectrophotometric titrations.  (Titration of H TPP(CF ) 2  3 4  (48a) with DBU and Et^SS).  Titrations were performed by the following procedure. The concentration of 48a was set to 9.66 x 10  -3  m M while varying the concentration of D B U within the range of 0-2.1 x 10  2  M.  The color change was noted immediately upon addition of D B U to the solution containing the porphyrin. Solutions were made up in H P L C grade C H C 1 and the UV-visible spectrum of each 2  2  batch was recorded. The same procedure was followed for the spectrophotometric titration using E t N . 3  198  The pK for the first deprotonation of H T P P ( C F ) (48a) a  2  analysis. According to the Lambert-Beer law, ^0  3  2  m  e  was determined by the following  4  following equations, (4.1) and (4.2) can be  written with the assumption that only the porphyrin species contributes to the absorbance at the  -^463  £463'Q-I2P ^~'~ ^463'CHP-'^  —  -  -A-513 — 5lVQ-I2P'^~'~  (4-1)  ( - )  £  4  selected wavelengths, where A  and A  4 6 3  2  are the total absorbances, s ^ , S ™ , s " , and S™~are 2  5 1 3  3  the extinction coefficients of the free-base porphyrin porphyrin mono anion (HP ), C -  H 2 P  3  3  (H P; P ~ = dianion of 48a) 2  2  and the  and C,. ,- are the concentrations of H P and H P " at 463 and n  2  513 nm, respectively, and / is the cell path length, 1 cm. Given the molar extinction coefficients and absorbances, the concentrations of the free-base and the mono anion are determined by the following equations (4.3) and (4.4).  &  -|-yi  prj  |H 1 J -  HP- * HP- A J I J 513 1J -"-463 tuj 463 -"513 &  J  2  H 2  p  H  p_  FC  H  V  2  FC  E 2 A nl  J  H p  H  /A  p.  (4.3)  513 463 463 513  FC  J  H  2  -E 2 A  P  P  P  H  FC  H  P  -  oB 2 H  P  P  p  H  P  "  V*' V  ^463 513 "" 513 463  P  B  B  Also, the relationships between concentrations of protonated D B U ( D B U H ) , H P , initial +  D B U , and D B U at each titration point are written as (4.5) and (4.6).  P B U H ] = [HP"! (4.5) +  PBU] = pBU] - pBUH ] +  0  (4.6)  199  K  The equilibrium constants  H2P  and i<C  DBU  for deprotonation of H P and D B U H  +  2  are  written as (4.7) and (4.8).  H P^HP + H  +  K  H2P  2  DBUH -DBU + H +  =  ]  K  +  (4.7)  = pBUPT]  DBU  1  (-) 4  8  The equilibrium constant for the H P - D B U reaction can be rearranged as (4.9). 2  H P + D B U ^ HP'+ D B U H  K= ^ ^ B U ]  +  2  = W*DBU  1  ^  (4-9')  Logarithm of both sides of (4.9) gives:  |H,P1  ^S  =  PBUH ] +  P  I  C  +  L  O  G  W  (4  -  9)  Analysis of titration data using (4.3) - (4.6) and (4.9") should give a straight line with the slope of 1 and the intercept of pK.  K=pK -pK =ApK  P  H2P  Dm  t  (4.10)  (Spectrophotometric titration of48e with pyridine and imidazole). C H C 1 and pyridine were distilled 2  2  and degassed by three freeze-pump-thaw cycles, and dried over activated molecular sieves  (4A).  200  A C H C 1 solution of Co(rPP(CF ) ) (48e) 2  2  3  4  (8.60 x 10" mM) in a 1 cm path length cuvette was  titrated with a pyridine solution (0 - 3.4 x 10  3  -1  M) prepared in CH C1 . Titration was performed 2  2  in a N glove bag. After each injection of the titer, the cuvette was tighdy capped with a Teflon 2  top to take out to UV-visible spectral measurements. In order to make sure that the reaction reached equikbrium, the UV-visible spectrum was monitored for 20 min after each titration. For higher concentrations of pyridine, neat pyridine was used. The concentrations of the species in the cuvette were corrected with the volume of the added titer. The same procedure was followed for the titration using imidazole. For higher concentrations of imidazole, solid was direcdy added to the cuvette. The binding constant was determined according to the following analysis. ^ The 22  binding constant is written as (4.11).  K CoP + B ^ C o P B ,  [CoPB] K-^pj.pjj  (4.11)  CoP: four-coordinate Co(TPP(CF3)4) (48e), B: pyridine or imidazole, CoPB: five-coordinate Co(II) porphyrin pyridine complex.  The mass balance regarding Co complexes is written as (4.12).  [CoP] + [CoPB] = [CoP]  0  (4.12)  [CoP], [CoPB], and [CoP]o: concentrations of CoP and C o P B during the titration and the initial concentration of CoP, respectively.  From (4.11) and (4.12), (4.13) is obtained.  [CoP] K  P]  + 1 =  [CoP]  0  ( - ) 4  13  According to the Lambert-Beer law,  201 A = e [ C o P ] , / = l c m (4.14) 0  0  A = s'[CoPB] = £'[CoP] F  f  (4.15)  0  A = s [CoP] + e'[CoP-B] (4.16)  Ao, Af, and A: the absorbances initially and finally, and during the titration, respectively, at the monitored wavelength. 8 and £': the extinction coefficients of CoP and CoPB at the wavelength. [CoPBJf: the final concentration of CoPB.  From (4.14), (4.15), and (4.16), (4.17) is obtained.  [CoP]  A-A  f  ^  A  /  )  Substitution of (4.13) into (4.17), rearranging and taking the log of the resultant equation gives (4.18).  L 0 G  (A^)  =  1  ° ^ 8  +  L  0  G  [  B  ]  ( 4  -  1 8 )  The concentration of B is obtained from (4.19).  [B] = [B] - [CoPB] = [B] - ([CoP] - [CoP]) = [B] - [ C o P ] - ^ tot  [B] ot: t  tot  0  tot  0  (4.19)  the total concentration of the base.  VA'  Thus, the plot of log [B] vs. log ^ ^ J should give a straight line with the slope equal to 1. The y intercept is the log K value.  202  Gas c h r o m a t o g r a p h y . For the analysis of cyclohexane oxidation, a typical temperature program was 40 °C (3 min) -» 20 ° C / m i n -» 220 °C (10 min). Injection temp, and F I D temp.: 220 °C. Retention times for CH C1 , cyclohexane, cyclohexanol, and iodobenzene were 1.02, 2  2  1.23, 5.36, and 7.40 min, respectively.  For the analysis of cyclohexene oxidation, the program  was 25 °C (3 min) — 20 ° C / m i n — 220 °C(10min). Injection temp.: 180 °C. F I D temp.: 220 °C. Retention times for CH C1 , cyclohexene, cyclohexene oxide, and iodobenzene were 1.25, 1.80, 2  2  6.48, and 7.48 min, respectively.  D. P r e p a r a t i o n of m a t e r i a l s 5 1 ,0 1 ,5 2 ,0 T e t r a p h e n y p lo r p h y r n i ( H T P P ) (2a).  The porphyrin was synthesized by a  2  published  procedure.  64  UV-vis (Ct^CL):  A,  max  (nm)  418 (Soret),  514,  549,  590,  646.  'H N M R (CDC1 ): 8 -2.76 (s, 2 H , N H ) , 7.75 (m, 12H, phenylp- and m-H), 8.22 (m, 8H, phenyl 3  o-H), 8.86 (s, 8H, pyrr-P-H); ( Q D ^ : -2.13 (s, 2 H , N H ) , 7.44 (m, 12H, phenyl p- and m-H), 8.10 (m, 8H, phenyl o-H), 8.91 (s, 8H, pyrr-P-H). The spectroscopic characteristics of this compound compare well to those reported in the literature.  64  5 , 1 0 , 1 5 , 2 0 T e t r a p h e n y l p o r p h y r i n a t o z i n c ( I ) ( Z n ( T P P ) ) (2b). synthesized by a published procedure.  68  UV-vis ( C H ^ L ) : A,  max  The porphyrin was  (nm) 419 (Soret), 548, 582.  *H N M R (CDCI3): 5 7.73 (m, 12H, phenyl p- and m-H), 8.08 (m, 8H, phenyl o-H), 8.90 (s, 8H, pyrr-P-H). The spectroscopic characteristics of this compound compare well to those reported in the literature.- " 3  6  C h l o r o ( 5 , 1 0 , 1 5 , 2 0 t e t r a p h e n y l p o r p h y r i n a t o ) i r o n ( I )( F e ( T P P ) C l ) (2d).  Metallation  using FeCl and oxidation to the Fe(III) complex were achieved by a published procedure. 2  69  203  ' H N M R (CDCL): 8 5.11 (s, 4 H , phenyl o-H), 6.39 (s, 4H, phenyl p-H), 7.98 (s, 4 H , phenyl o-H), 12.17 (s, 4 H , phenyl m-H), 13.32 (s, 4 H , phenyl m-H), 79.46 (s, 8H, pyrr-p-H). The spectroscopic characteristics of this compound compare well to those reported in the literature. ! 23  5 , 1 0 , 1 5 , 2 0 T e t r a k i s ( p e r f l u o r o p h e n y l ) p o r p h y r i n ( H T P F P P ) (4a). 2  synthesized by a published procedure . UV-vis (CH OJ: 232  2  X  mxi  The porphyrin was  (nm) 410 (Soret), 505, 535, 582,  635. ' H N M R (CDC1 ): 8 -2.50 (s, 2 H , N H ) , 8.80 (s, 8H, pyrr-p-H).  1 9  3  F N M R (CDC1 ),: 5 (vs. 3  CFCI3) -137.0 (d, 2F, aryl o-F), -151.7 (t, IF, arylp-¥), -161.8 (m, 2F, aryl m-F). The spectroscopic characteristics of this compound compare well to those reported in the literature.  233  5 , 1 0 , 1 5 , 2 0 T e t r a k i s ( p e r f l u o r o p h e n y l ) p o r p h y r i n a t o z i n c ( I I ) ( Z n ( T P F P P ) ) (4b).  Zn(II)  was inserted into 4 a by a published procedure using Z n ( O A c ) - 2 H 0 . UV-vis (CF^CL): 6 8  2  \nax (nm) 414 (Soret), 544. ' H N M R (CDC1 ): 5 9.17 (s, 8H, pyrr-p-H).  2  , 9  3  F N M R (CDC1 ): 8 (vs. 3  CFC1 ) -138.5 (d, 2F, aryl o-F), -154.8 (t, IF, arylp-F), -163.7 (m, 2F, aryl m-F). The spectroscopic 3  characteristics of this compound compare well to those reported in the literature.78> 4 23  7 8 ,1 ,7 1 ,8 T e t t a b r o m o 5 1 ,0 1 ,5 2 ,0 t e t r a p h e n y p lo r p h y r n i  (H TPPBr )( 4 5 a ) . The 2  4  porphyrin was synthesized by published proceduresl85,186 except for the purification process. Analytically pure porphyrin was obtained by the following procedure. Crude product (100 mg)  was dissolved completely in hot chloroform (30 mL) and silica gel (30 m L — 15 g, 70 - 230 mesh) was mixed into the solution. The solvent was removed at room temperature in a fume hood. The color of the porphyrin-adsorbed silica gel was brown. The brown silica gel was loaded on top of silica gel (2 x 20 cm) wet with benzene/hexane 50:50 (v/v) and the impurities (mainly H T P P B r ) were eluted with the solvent of the same composition. The main brown fraction was 2  3  204  coUected with  100  % benzene.  UV-vis ( C F L A ) :  ^(nm)  436 (Soret),  534,  616,  686.  n N M R (CDC1 ): 5 -2.83 (s, 2H, N H ) , 7.78 (m, 12H, phenyl p- and m-H), 8.18 (m, 8H, phenyl  l  3  o-H), 8.68 (d, 4 H , pyrr-p-H); ( Q D ^ : 8 -2.69 (s, 2H, N H ) , 7.50 (m, 12H, phenyl p- and m-H), 8.04 (m, 8H, phenyl o-H), 8.54 (d, 4 H , pyrr-p-H); ( C F C 0 D ) : 8 8.37 (m, 12H, phenyl p- and 3  2  m-H), 8.68 (m, 4 H , phenyl. o-H), 8.92 (m, 4H, phenyl o-H), 8.75 (s, 4H, pyrr-p-H). The spectroscopic  characteristics of this compound compare well to those reported in the  Uterature. 185,186  2,3,12,13-Tetrabromo-5,10,15,20-tetraphenylporphyrinatozinc(II) (Zn(TPPBr ))(45b).  Zn(II)  4  Zn(OAc) -2H 0. 2  68  2  UV-vis (CH.CL): X  was  inserted  into  45a  by  a published  procedure  using  L R - M S (EI, 300 °C): M ( m / z ) = 993 , calcd. for C H B r N B r : 993.6888. +  44  24  4  4  (nm) 430 (Soret), 560, 598. H N M R (DMSO-d,): 8 8.61 (s, 4 H , pyrr-P-H), ]  m a x  8.02 (m, 8H, phenyl-o-H), 7.80 (m, 12H, phenyl-/? and m-H). The spectroscopic characteristics of this compound compare well to those reported in the literature. -^ 2  2,3,12,13-Tetrabromo-5,10,15,20-tetraphenylporphyrinatocopper(II) (Cu(TPPBr ))(45c).  Cu(II)  4  Cu(OAc) -H 0. 2  2  6 8  was  inserted  into  45a  by  a  published  procedure  using  L R - M S (EI, 300 °C): M ( m / z ) = 991 , calcd. for C ^ H ^ B r . N . C u : 991.8828.  UV-vis (CHjCL): A,  +  max  (nm) 426 (Soret), 553, 586. The spectroscopic characteristics of this  compound compare well to those reported in the literature. - ^ 2  3  2,3,12,13-Tetrabromo-5,10,15,20-tetraphenylporphyrinatonickel(II) ( N i ( T P P B r ) ) ( 4 5 d ) . Ni(Ii) was inserted into 45a by a published procedure using N i C l . 4  2  MS (EI, 300 °C): M ( m / z ) = +  987,  calcd. for C ^ H ^ B r . N . N i :  6 8  LR-  987.0528. UV-vis (CH.CL):  205  X  max  (nm) 428 (Soret), 544, 538.  The spectroscopic characteristics of this compound compare  well to those reported in the literature.235  Chloro(2,3,12,13-Tetrabfomo-5,10,15,20-tetraphenylpotphyrinato)iron(III) ( F e ( T P P B r ) C l ) (45e). Insertion of Fe(II) and formation and purification of this Fe(IIi) 4  complex were achieved by published procedures^,! 90 UV-vis ( C H j C y :  (nm) 433 (Soret),  520, 591, 714. ' H N M R (CDC1 ): 5 4.77 (s, 4 H , phenyl o-H) 6.59 (s, 4 H , phenylp-H), 7.41 (s, 4 H , 3  phenyl o-H), 12.46 (s, 4 H , phenyl m-H), 13.19 (s, 4 H , phenyl m-H), 79.49 (s, 4 H , pyrr43-H). The spectroscopic  characteristics of this compound compare well to those reported in the  literature.191  2,3,7,8,12,13,17,18-Octabromo-5,10,15,20-tettaphenylporphyrinatocopper(II) ( C u ( T P P B t ) ) (7c). The porphyrin was synthesized by a published procedure.^. L R - M S (EI, 8  300 °C): M ( m / z ) = 1307, calcd. for C ^ H ^ B r ^ C u : 1307.4908. UV-vis (CPECy: +  ^(nm)  365, 448 (sh), 466 (Soret), 581, 625. The spectroscopic characteristics of this compound compare well to those reported in the literature.75  S o d i u m trifluoromethylacetate  (CF C0 Na). 3  2  N a O H aqueous solution (0.75 M) was  slowly added to a solution of trifluoroacetic acid, 99 % (5.76 m L (75 mmol) in 100 m L H 0 ) . 2  This solution was stirred and the p H monitored. As the p H of the solution approached 5 - 6 , the N a O H solution to be added was diluted to about 0.1 M and further added to the solution of p H 5 - 6 . Near p H 7 more diluted N a O H solution was used to adjust the p H at 7.0. The neutralized solution was transferred to a 500-mL round-bottomed flask and most of the water was removed  206  by a rotary evaporator. A hygroscopic white solid was obtained. The wet solid was transferred to a vial and dried under in vacuo at 100 °C overnight. The product was kept in a desiccator.  T r f i u lo r o m e t h y c la d m u im ( C F C d B r + (CF)Cd)). This reagent was synthesized by the 3  3 2  published procedure. 139 Trifluoromethylcadmium reagent was obtained as ca. 1 M solution of trifluoromethyl anion in D M F .  1 9  F N M R (DMSO-d,): 5 (vs. CFCL) -33.2 (CF CdBr), and -33.9. 3  These chemical shifts agree with the reported values. 39 ((CF ) Cd), each of which was 1  3  accompanied by the satellite peaks by  i n  C d and  113  2  C d . J ( C d - F ) : C F C d B r , 370.9; (CF ) Cd, ,,3  19  3  3  2  423.7 Hz. J ( C d - F ) : CF CdBr, 355.9; (CF ) Cd, 404.8 Hz. The concentration of CF " was m  ,9  3  3  2  3  determined by the ratio of the peak integration to the internal reference, 3-fluorotoluene. The spectroscopic  characteristics  of this compound compare well to those reported in the  literature. 139  P T r i f l u o r o m e t h y l w e s o t e t r a p h e n y l p o r p h y r i n s . (Pyrolysis of CFjCO^a) 100 m L round-bottom flask equipped with a N  2  A  one-neck  inlet was charged with C F C 0 N a (2.70 g, 3  19.8 mmol), C u l (1.52 g, 8.00 mmol), Zn(TPPBr ) (45b) 4  2  (0.500 g, 0.503 mmol), dry D M F  (15 mL) and toluene (5.5 mL). The flask was equipped with a distillation apparutus and toluene was removed during the first one hour at 120 °C under a N stream. The reaction mixture was 2  then heated up to 150 °C. C0 (g) generation started at about 145 °C. The mixture was allowed 2  to cool after 1 h and D M F was removed by a rotary evaporator. C H C 1 (50 mL) was added to 2  2  the green product and the resulting solution was passed through a short silica gel column to remove the inorganic salts. The volume of CH Cl was reduced to about 10 mL, T F A (4 mL) was 2  2  added and the mixture was refluxed for 1 h. The brown solution was diluted to ~100 m L with C H C 1 and washed with the same amount of water 3 times. Silica gel T L C of the free-base 2  2  207  porphyrin mixture showed three distinctive spots for H T P P ( C F ) 2  and H T P P ( C F ) (48a) 2  3  4  3  ( 4 6 a ) , H TPP(CF ) ( 4 7 a ) ,  2  2  3  (Rf = 0.58, 0.47, and 0.09, respectively. CH Cl :hexane=5:5 (v/v)). In 2  2  addition to these three spots, some less intensive spots were observed between 47a Compound 46a,  47a,  3  and  48a.  and 48a were separated by silica gel column, by changing the composition  of solvent mixture gradually (CH Cl /hexane = 30/70 -» 50/50 -» 70/30 — benzene (100)). 2  Since the solubility of 48a  2  was low in this solvent system, the mixture of 46a,  47a,  and 48a  was  pre-adsorbed on a minimal amount of silica gel before column chromatography. The solvents were removed from each fraction to yield 46a  (60 mg, 16%), 47a  (120 mg, 29%), and  48a  (11 m g . 2 . 5 % ) .  (Metathesis of trifluoromethylcadmium) A typical example of this reactions is shown below. As shown in chapter II, reaction temperatures and times were varied. Trifluoromethylcadmium reagent (14 mL, ca.l M) and dry H M P A (14 mL) were transferred to a two-neck 100 m L roundbottom flask and the mixture was cooled down to 0 °C and stirred for 3 min under N . T o this 2  brown solution CuBr (1 g, 7 mmol) was added and the mixture was stirred until the CuBr was dissolved at room temperature. Zn(TPPBr ) (45b)  (0.5 g, 0.5 mmol) was then added and the  4  mixture was heated at 90 °C for 7 h under N . After the mixture was cooled to room 2  temperature, D M F was removed by a rotary evaporator at 100 °C and small amount of H M P A was  removed  at  2 - 3 mmHg  at  100 °C.  HMPA  could  not  be  removed  completely.  Trifluoromethylated porphyrins were extracted with petroleum ether (35-60) until the green color of the petroleum ether became weak. The resultant residue which remained after the petroleum-ether extraction was dissolved in minimum amount of C H C 1 and approximately the 2  2  same volume of silica gel (230 - 400 mesh) was added to adsorb the impurities and porphyrin products. After drying the pre-adsorbed silica gel for several hours at room temperature, it was  208  packed in a short column without additional silica gel and washed with benzene. Only the green porphyrin products were extracted and the brown impurities remained on the silica gel phase. The green benzene solution was then combined with the petroleum-ether extracts. Volatile solvents were removed in vacuo, H M P A * was distilled off at 100 - 110 °C at 2 - 3 mmHg. The product was dissolved in C H C 1 and filtered. C H C 1 (50 mL) and T F A (10 mL) were added to 2  2  2  2  the green solid and the mixture was refluxed over a steam bath for 30 min until the color became dark orange. The mixture was diluted with CH C1 , washed with 4 M HC1, distilled water, and 2  2  10 % aq. N a H C 0 . CH C1 , was removed and the free-base mixture was dissolved in a miriimum 3  2  2  amount of benzene and adsorbed on silica gel (230 - 400 mesh, same volume as the benzene solution). After drying at room temperature in the fume hood, the pre-adsorbed silica gel was loaded on top of a wet silica gel bed prepared using 5 x volume to the amount used for pre-  adsorption and chromatographed with CH Cl /hexane  (30/70 (v/v) -»• 50/50)  to isolate  H T P P ( C F ) (46a)  (86 mg,  remaining  2  2  3  2  (34 mg,  9 %)  and  2  H T P P ( C F ) (47a) 2  3  3  21 %).  The  porphyrins on the column were washed with benzene/acetone (90/10 (v/v)). The solvents were removed and the porphyrins were dissolved in benzene and pre-adsorbed on a minimum amount of silica gel (230 — 400 mesh). Pre-absorbed silica gel was place on top of a wet silica gel bed prepared using 7 — 8 x volume of silica gel to the amount used for pre-adsorption and flushchromatographed  with  benzene/cyclohexane/acetone  90/0/10)). Yield; H T P P ( C F ) (48a) 2  54a  3  4  (20/80/2 (v/v/v)  ->•  (140 mg, 38 %), H T P P ( C F ) ( C F C F ) (52a) 2  3  3  2  3  50/50/2  -*  (47 mg, 10%),  (trace).  * Caution ! H M P A is a carcinogen and highly toxic. Distillation must be performed with an apparatus equipped with double traps in a fume hood.  209  46a  showed  a  single  mass  corresponding  to  P-bis(trifluoromethyl)-w^o-  tetraphenylporphyrin by mass spectroscopy. However, ' H N M R of 46a  did not show a clear  spectrum corresponding to a specific regioisomer. Two very close bands that could not be separated were recognized by T L C analysis of 46a (10/90(v/v)) as a solvent. close. Thus, 46a  1 9  F N M R of 46a  on a silica gel plate using CH Cl /hexane 2  2  showed two singlets whose chemical shifts were very  could be a mixture of regioisomers, 46a'  and 46a"  (p.71). The mixture of the  regioisomers was used throughout the experiments (e.g. UV-vis spectroscopy and cyclic voltammetry).  As for 47a,  the structure of the porphyrin was confirmed by the following analysis. There  are seven possible regioisomers for p-tris(trifluoromemyl)-^j'o-tetraphenylporphyrin in terms of the occupancy of the eight pyrrolic P-positions by three - C F groups (Figure 4-2). H N M R of !  3  47a  (Figure 2-15, p.120) showed one singlet and four doublets (AB quartet) for the five pyrrolic  P-protons. Four structures, 47-3,  47-4,  47-5,  and 47-6  are ruled out because the ' H N M R spectra  of these compounds would have to consist of three singlets and two doublets. 47-0, 47-2  are expected to show one singlet and four doublets. However, for 47-1  and 47-2,  47-1  and  in order to  satisfy the result of the H C O S Y spectrum (Figure 2-16, p.121), the positions of the N - H !  protons must be as shown in 47-1'  and 47-2'  (box in Figure 4-2). It is known that such tautomers  are not stable due to penetration of each proton into the van der Waals sphere of the other and a N - H tautomer with two inner protons on transannular nitrogens is the most probable. 141 Thus, 47-1  and 47-2  should be also ruled out, and 47-0  is the only possible structure for the synthesized  p-tris(trifluoromemyl)-^j'0-te1raphenylporphyrin.  In  other  words,  the  copper  assisted  trifluoromethylation occurs regiospecifically at the brominated sites, and side reactions such as rearrangement of - C F groups are unlikely. 3  210  F i g u r e 4-2. Possible isomers for P-ttis(tofluoromemyl)-wwo-tetraphenylporphyrin. Double bonds, N , and N - H were omitted for for clarity. N and N - H are shown in 47-1'  and 47-2'.  211  Physical data of 46a, 47a, 48a, 52a, and 54a  P B i s ( t r i f l u o r o m e t h y l ) 5 , 1 0 , 1 5 , 2 0 t e t r a p h e n y l p o r p h y r i n (H TPP(CF ) )( 4 6 a ) : 2  MS (EI, A.  m a x  250 °C):  M (m/z)  = 750,  +  calcd for Q H ^ F . N , :  (nm) (logs) 424 (5.49), 524 (4.19), 601 (3.62), 661 (3.86).  1 9  3 2  750.7448.  LR-  UV-vis (CH.CL):  F N M R (CDCL): 5 (vs. CFCL)  -52.7 (s), -52.8 (s).  7 , 8 4 7 T r i s ( t r i f l u o f o m e t h y l ) 5 , 1 0 1 5 , 2 0 t e t f a p h e n y l p o r p h y t i n ( H T P P ( C F ) 3 )( 4 7 a ) : )  L R - M S (EI, 250 °C): M (m/z)  = 818, calcd for C H F N :  +  ^max  2  4 7  2 7  9  4  3  818.7418. UV-vis (CHjCL):  (nm) Gogs) 440 (5.29), 550 (3.94), 590sh (3.51), 735 (4.13). ' H N M R (CDC1 ): 8 -1.73 (s,lH, 3  N H ) , -1.85 (s,lH, N H ) , 7.77 (m, 12H, phenyl-;* and m-H), 8.17 (m, 8H, phenyl-o-H), 8.70 and 8.57, 8.61 and 8.31 (2 A B q, J =5.06, 5.11 Hz, 4 H , pyrr-p-H), 8.76 (s, 1H, pyrr-P-H). F N M R 1 9  AB  (CDC1 ): 8 (vs. CFC1 ) -49.1 (m, 6F), -53.1 (s, 3F). C H N anal.(%), calcdforC H F N : C , 68.95; 3  3  4 7  2 7  9  4  H , 3.32; N , 6.84, found: C, 68.71; H , 3.38; N , 6.54.  7 , 8 ^ 7 4 8 T e t r a k i s ( t r i f l u o r o m e t h y l ) 5 , 1 0 , 1 5 , 2 0 t e t r a p h e n y l p o r p h y r i n  (H TPP(CF ) ) 2  3 4  ( 4 8 a ) : L R - M S (EI, 250 °C): M (m/z)= 887, calcd for C H F N : 886.7388. UV-vis (CH.CL): +  4 8  A.  max  ^max  (nm) dog s) (nm)  444(5.04),  463 (4.96),  580(3.81),  2 6  1 2  4  620sh (3.38),  832(4.23);  (QFLJ:  doge) 446 (5.11), 466 (5.03), 577 (3.94), 616sh (3.48), 822 (4.32). ' H N M R ( Q D ^ : 8  -1.42(s, 2 H , N H ) , 7.45 (m, 12H, phenyl-/* and p-H), 8.00 (s, 4 H , pyrr-p-H), 8.11 (m, 4 H , phenylo-H), 8.13 (m, 4 H , phenyl-o-H); ( C F C 0 D ) : 8 8.16 (m, 12H, phenyl-^ and p-H), 8.28 (s, 4 H , 3  2  pyrr-P-H), 8.55 (s, 8H, phenyl-o-H). . F N M R (QD^),: 8 (itr. CFC1 ) -49.6 (s). C H N anal.(%), 1 9  3  calcd for C H F N : C, 65.02; H , 2.96; N , 6.32, found: C, 65.00; H , 2.86; N , 6.17. 4 8  2 6  1 2  4  212  7 , 8 , 1 7 T r i s ( t r i f l u o r o m e t h y l ) 1 8 ^ (HTPP(CF)(CFCF)) ( 5 2 a ) : L R - M S (EI, 250 °C): M ( m / z ) = 936, calcd for C H F N : +  2  3 3  936.7458.  2  3  4 9  UV-vis (CH^l,):  X  m a x  (nm) (log s)  444(5.03),  468(5.01),  586(3.90),  2 6  1 4  4  628(3.55),  844 (4.36). H N M R ( Q D ^ : 5 -1.27 (s, I H , N H ) , -1.03 (s, I H , N H ) , 7.44 (m, 12H, phenyl m and 5  p-H),  7.92 (d, I H , pyrr-P-H), 7.96 (d, I H , pyrr-P-H), 8.03 (m, 8H, phenyl o-H), 8.22 (br d (maybe  overlapped two doublets), 2H, pyrr-P-H), in addition to these porphyrin peaks there were two sharp peaks at 1.40 (s, 2H) and 1.60 (s, 2H). These peaks diminish when D 0 is added. So 2  possibly these peaks are due to water. A residual water peak also appears at 0.4 ppm as usual case for the ' H N M R spectrum for C D . 6  F N M R (QD,),: 6 (vs. CFC1 ) -47.7 (m, 3F), -49.6 (m, 6F),  , 9  6  3  -82.3 (m, 3F), -98.2 (m, 2F). C H N anal.(%), calcd for C H F N - 0 . 7 5 C H : C , 53.18; H , 2.43; N , 49  26  14  4  6  6  5.64, found: C , 53.25; H , 2.54; N , 5.42.  5 4 a : L R - M S (+LSIMS): UV-vis (CF^CL): X  miLX  M (m/z)  = 987,  +  calcd.  for  C H F N : 5 0  2 6  1 6  4  986.7528.  (nm) 444, 486, 588, 648.  Color observation (in solid): 46a;  purple, 47a;  brown, 48a  and 52a;  golden brown in solid.  48a and 52a are tangerine in color in C H C 1 containing T F A (0.5 %). 2  2  2 , 3 , 1 2 , 1 3 T e t t a k i s ( t r i f l u o f o m e t h y l ) 5 , 1 0 , 1 5 , 2 0 t e t i a p h e n y l p o r p h y r m a t o z i n c ( I I ) ( Z n ( T P P ( C F ) ) ( 4 8 b ) . Z n ( O A c ) - 2 H 0 (37 mg, 0.17 mmol) in M e O H (10 mL) was added to a 3 4  2  2  brown suspension of H T P P ( C F ) ( 4 8 a ) (50 mg, 0.056 mmol) in C H C l ( 1 0 m L ) 2  3  4  at room  3  temperature. The color instandy changed to a bright green and solids were completely dissolved. The mixture was stirred for 30 min at room temperature, then CHC1 (100 mL) was added and 3  the mixture was then washed with water (2 x 100 mL). The volume of the green CHC1 solution 3  was reduced in vacuo and dried over anhydrous N a S 0 . Filtration and removal of the solvent 2  4  213  gave a green powder of 48b. The yield was 52 mg (98 %). UV-Vis (CHjCL): k  mm  (nm) (log e)  442 (5.37), 662 (4.31). I H N M R (CDC1 ): 8 7.70 (m, 12H, phenyl-w and p-H), 8.07 (m, 8H, 3  phenyl-o-H), 8.43 (s, 4 H , pyrr-p-H). F N M R (CDC1 ): 5 (vs. CFC1 ) -48.3. C H N anal.(%), calcd 1 9  3  3  for C ^ H ^ F ^ N . Z n : C , 60.68; H , 2.55; N , 5.90, found: C , 60.60; H , 2.56; N , 5.75.  2,3,12,13-Tettalds(trifluofomethyl)-5,10,15,20-tetraphenylpotphyfinatocobalt(II) ( C o ( T P P ( C F ) ) (48e). 3  4  H T P P ( C F ) (48a) (50 mg, 0.056 mmol) 2  3  4  and C H C l ( 1 0 m L ) 3  placed in a 50 mL-round-bottomed flask. C o C l (22 mg, 0.17 mmol) in M e O H ( l O m L ) 2  were was  added to the brown suspension in the flask and the mixture was refluxed for 30 min. The color of the solution changed from brown to bright green. The green solution was diluted with CHC1 (100 mL) and washed with water (2 x 100 mL). The amount of the green CHC1 solution 3  3  was reduced in vacuo and dried over anhydrous N a S 0 . Filtration and removal of the solvent 2  4  gave a green powder of 48e. The yield was 51 mg (96 %). H R - M S (EI, 220 °C): M (m/z) = +  943.11455 (100%), calcd for C H F N C o : 943.11413. UV-Vis 4 8  2 4  1 2  4  (CPLjjL): X  max  (nm) (log s)  440(5.06), 636 (4.32). ' H N M R (CDC1 ): 8 9.55 (m, 12H, phenyl-/*? and p-H), 13.57 (bs, 8H, 3  phenyl-o-H), 15.41 (bs, 4H, pyrr-p-H).  1 9  F N M R (CDC1 ): 8 (vs. CFCL) -54.3. C H N anal.(%), 3  calcd for C H F N C o : C , 61.09; H , 2.56; N , 5.94, found: C , 61.41; H , 2.62; N , 5.78. 4 8  2 4  1 2  4  Chloro(2,3,12,13-tetiakis(trifluoromethyl)-5,10,15,20tettaphenylporphyrinato)iton(III)  ( F e ( T P P ( C F ) ) C l ) (48f). 3  4  H T P P ( C F ) (48a) (45.3 mg, 2  3  4  0.0511 mmol) and lithum bis(trimethylsilyl)amide (122.2 mg, 0.730 mmol) were dissolved in dry T H F (4.5 mL) at room temperature under N . The color of the solution became dark orange. 2  The solution was stirred for 5 min in a septum-sealed flask. Under an N atmosphere anhydrous 2  FeCl (87.2 mg, 0.692 mmol) was added to the solution. The mixture was then warmed at 50°C. 2  214  The color of the solution gradually changed to dark green in 3 min. The solution was stirred under N  2  at room temperature for 2 h. The color further changed to brighter green. T L C using  an alumina plate (CH Cl /petroleum ether = 50/50(v/v)) showed a weak brown spot moving 2  2  fastest and a major green band smearing from the origin. After the solvent was removed from the reaction mixture, the product was dissolved in CH Cl /petroleum ether (50/50 (v/v)(10 mL) 2  2  and was chromatographed on an acidic alumina column. The green color of the compound turned  brown  on  the  column.  The  first  fraction  was  identified  as  the  u—oxodimer  (Fe(TPP(CF ) ] 0 (61) from mass spectrometry. The slow moving green fraction was washed 3  4  2  with acetone and combined with the Li-oxodimer (61). The solvent was removed, the product was dissolved in C H C 1 (50 mL) and washed with cold 6 M HC1 (50 mL) until the organic phase 2  2  turned bright green. The C H C 1 2  2  phase was collected and dried over anhydrous N a S 0 . 2  4  Filtration and removal of the solvent gave a dark blue powder of 48f (31.0mg, 62.3%). Fe((TPP(CF ) )Cl (48f): L R - M S (+LSIMS): M ( m / z ) = 940, calcd. for C H F N F e : 940.5728. +  3  UV-Vis  4  4 8  (CH CL): 2  A.  m a x  (nm) (log 8) 452(4.76), 618(4.12). ' H N M R  2 4  1 2  4  (CDCL): 5 4.04 (s, 4 H ,  phenyl-^-H), 6.5 - 3.5 (bs, 8H, phenyl-o-H), 14.52 (s, 8H, phenyl-w-H), 77.15 (bs, pyrr-p-H, 4H). 1 9  F N M R (CDC1 ): 8 (vs. CFCL) 0.05 (s).  [Fe(TPP(CF ) ] 0 (61): L R - M S (+LSIMS): M ( m / z ) = +  3  1897  (93 %),  940  (100%),  calcd.  3  for  4  2  C H F N OFe : %  4 8  2 4  8  2  1897.145.  UV-Vis  (CH.CL):  ?Vax (nm) (relative intensity) 435 (1.0), 700 (0.3). ' H N M R (CDC1 ): 8 6.55 (bs, 8H, phenyl-H), 3  7.36 (bs, 8H, phenyl-H), 7.72 - 8.12 (m, 24H, phenyl-H), 11.52 (bs, 4 H , pyrr-p-H), 12.19 (bs, 4 H , pyrr-p-H).  , 9  F N M R (CDCL): 8 (vs. CFC1 ) -46.8 (s. 12F),-45.2 (s, 12F). 3  Chloro(23,12-tris(trifluoromethyl)-13-pentafluoroethyl-5,10,15,20tetraphenylporphyrinato)iron(III) ( F e ( T P P ( C F ) ( C F C F ) ) C l ) (52c). This porphyrin was 3  3  2  3  synthesized in a similar method as for the synthesis of Fe((TPP(CF ) )Cl (48f). The yield was 3  4  215  42mg(76%  based  C^H^N.Fe:  on  50 mg of 5 2 a ) .  L R - M S (+LSIMS): M ( m / z ) +  940.5728. UV-Vis (CH.CL): A.  MAX  = 940,  calcd. for  (nm) (log e) 452(4.76), 618(4.12). ' H N M R  (CDCL): 5 3.10 (m, 4 H , phenyl-^-H), 4.80 (bs, 8 H , phenyl-o-H), 14.75 (s, 2 H , phenyl-w-H), 15.22 (s, 6 H , phenyl-^-H), 73.52 (bs, 1H, pyrr-p-H), 74.65 (bs, 3 H , pyrr-p-H).  1 9  F N M R (CDC1 ): 3  5 (vs. CFC1 ) -66.3 (s, 3F), -13.8 (b, 2F), -6.2 (s, 3F), 1.1 (s, 3F), 14.5 (s, 3F). 3  P M e t h y l m e s o t e t r a p h e n y l p o r p h y r i n s .  CuBr (l.OOg ,7 mmol) and C H L i ( 1 0 m L 3  of  1.4 M solution in Et 0,14 mmol) were mixed at -80 °C under N in a flame-dried 50-mL one2  2  neck round-bottomed flask with a stopcock side arm that was sealed with a rubber septum. The mixture  was  stirred  at - 8 0 ° C  under  N  2  until  the  CuBr  Zn(TPPBr ) ( 4 5 b ) (233 mg , 0.235 mmol) was added under a N 4  was  dissolved  completely.  stream to the solution. The  2  color of the mixture became green instandy. The solution was kept in an oil bath at 3 2 ° C . A small amount of mixture was withdrawn with a syringe to monitor the U V - V i s spectrum of the mixture during the reaction. The solids that built up at the edge of the solution were dissolved using a sonicator. The reaction was run for 24 h. There was no difference in UV-Vis spectra between 6 and 24 h. After the reaction was complete, dilute HC1 (5 mL) was carefully added. 100 m L of C H C 1 was added and the solution was washed with H 0 (100 mL). A red powder of 2  2  2  the mixture of Zn(II) porphyrins was obtained by removing CH C1 . In order to remove the —Br 2  2  groups remaining on the pyrolic P-positions, the Zn(II) porphyrins were refluxed in D M F (not dried) in the presence of CuBr for 2 h. After this reaction was complete, D M F was evaporated. Zn(II) porphyrins were dissolved in C H C 1 and CuBr was removed by filtration. A red powder 2  2  was obtained by removing CH C1 . Since the product was poorly soluble in common organic 2  2  solvents and a T L C investigation did not give a satisfactory result, the Zn(II) porphyrins were then demetallated. The red powder (140 mg) was then dissolved in T F A (3 mL) and refluxed for  216  1.5 h. Demetallation was complete as confirmed by disappearance of the Soret peak at 416 nm. The resultant green mixture gave a broad Soret band at 446 nm and a Q band at 656 nm in C H C 1 The mixture was cooled down to room temperature and diluted with CHC1 (100 mL). 2  2  3  The green solution was washed with H O (2 x 100 mL), with 7.5 % aq. N a H C 0 z  (1 x 100 mL),  3  and with H 0 (1 x 100 mL). The amount of the CHC1 solution was reduced to ca.5 mL. Free2  3  base porphyrins were mixed with approximately the same amount of silica gel (70 - 230 mesh). The silica gel was dried in air at room temperature in the fume hood. The porphyrin-preadsorbed silica gel was placed on the top of the silica gel column prepared in CHC1 . Two fractions were 3  obtained from the column chromatography with CHC1 . 3  Each  fraction contained  two  compounds. The compounds in the first fraction were chromatographed on a silica gel column with CH C1 /petroleum ether and the separation yielded H T P P ( C H ) (56a) (less than 0.5 mg) 2  2  2  and H T P P ( C H ) 2  gel  3  2  column with  H TPP(CH ) 2  3  3  3  (57 a) (29 mg, 19 %). The remaining mixture was chromatographed on a silica CH C1 2  containing 2 vol% of  2  (58a) (26 mg, 17 %) and H T P P ( C H ) 2  3  4  acetone  and the  separation  yielded  (59a) (24 mg, 15 %).  Physical data of 56a, 57a, 58a, and 59a  p-Methyl-5,10,15,20-tettaphenylporphyrin  (H TPP(CH )) (56a): L R - M S 2  3  M ( m / z ) = 628, calcd. for C H N : 628.7778. UV-vis (CH^CL):  (nm) 417 (Soret), 514, 548,  +  4 5  3 2  (EI, 250 °C):  4  588, 644.  p-Dimethyl-5,10,15,20-tettaphenylporphyrin  (H TPP(CH ) ) (57a): 2  3  L R - M S (EI,  2  250 °C): M ( m / z ) = 642, calcd. for C H N : 642.8048. UV-vis (CH.Ch): X +  4 6  3 4  4  418 (5.69), 514 (4.35), 546 (3.76), 587 (3.87), 640 (3.75).  m a x  (nm) (log e)  217  2 , 3 , 1 2 T r i m e t h y l 5 , 1 0 , 1 5 , 2 0 t e t f a p h e n y l p o r p h y r i n (H TPP(CH ) )( 5 8 a ) : L R - M S (EI, 2  3 3  250 °C): M ( m / z ) = 656, calcd. for C H N : 656.8318. UV-vis (CH CL): X +  4 7  3 4  4  2  m a x  (nm) (log e)  419 (5.60), 516 (4.29), 584 (3.66), 644 (3.24). ' H N M R (CDCL): 5 -2.67 (s, 1H, N H ) , -2.94 (s, 1H, N H ) , 2.42 (s, 3 H , - C H ) , 2.44 (s, 3H, - C H ) , 2.59 (s, 3H, - C H ) , 7.70 (m, 12H, phenyl-/* and p-H), 3  3  3  8.06 (m, 6H, phenyl-o-H), 8.17 (m, 2 H , phenyl-o-H), 8.63, 8.56 (ABq, 2 H , pyrr-p-H), 8.54 (m, 2 H , pyrr-P-H), 8.59 (s, 1H, pyrr-p-H). C H N anal.(%), calcd for C H N - 0 . 5 H O : C, 84.78; H , 5.68; 47  36  4  2  N , 8.41, found: C , 84.79; H , 5.43; N , 8.48.  2 , 3 , 1 2 , 1 3 T e t r a m e t h y l 5 , 1 0 , 1 5 , 2 0 t e t r a p h e n y l p o r p h y r i n (H TPP(CH ) )( 5 9 a ) : LR2  3 4  MS (EI, 250 °C): M ( m / z ) = 670, calcd. for C H N : 670.8588. UV-vis (CH CL): X +  4 8  3 8  4  2  m3X  (nm)  420 (Soret), 520, 588, 640. H N M R (CDCL): 5 -2.77 (s, 2 H , N H ) , 2.39 (s, 12H, - C H ) , 7.71 (m, ]  3  12H, phenyl-/* and p-H), 8.07 (m, 8H, phenyl-o-H), 8.44 (s, 4 H , pyrr-P-H); ( Q D ) : 5 2.38 (s, 12H, 6  - C H ) , 7.40 (m, 12H, phenyl-/* and p-H), 7.97 (m, 8H, phenyl-o-H), 8.75 (s, 4 H , pyrr-P-H); 3  ( C F C O D ) : 8 2.57 (s, 12H, - C H ) , 8.40 (m, 12H, phenyl-/* and p-H), 8.66 (s, 4 H , phenyl-o-H), 3  z  3  9.01 (s, 4 H , phenyl-o-H), 8.80 (s, 4H, pyrr-p-H). C H N anal.(%), calcd for C^H^N.-O.SCHCL,: C, 79.73; H , 5.31; N , 7.67, found: C, 79.35; H , 5.31; N , 7.41.  Color obsevations: 57a,  58a,  and 59a  were purple in the solid phase and green in C H C 1 2  2  containing 0.5 % T F A .  2 , 3 , 1 2 , 1 3 T e t r a m e t h y l 5 , 1 0 , 1 5 , 2 0 t e t r a p h e n y l p o r p h y r i n a t o z i n c ( I )( Z n ( T P P ( C H ) ) ) 3 4  ( 5 9 b ) . Zn(TPP(CH ) ) (59a) 3  4  (20 mg,  0.030 mmol)  was  dissolved  in  CHCl (20mL). 3  Z n ( O A c ) - 2 H 0 (20 mg, 0.091 mmol) was dissolved in M e O H (10 mL) and added to the CHC1 2  2  3  solution of porphyrin. The mixture was refluxed for 1 h. The color of the solution changed from  218  purple to red. After the solvents were removed by a rotary evaporator, the product was dissolved in CHCI3 (60 mL) and washed with water (3 x 60 mL). The solution was dried using anhydrous N a S 0 . Filtration and evaporation of the CHC1 solution yielded a red powder of 59b (18 mg, 3  3  4  80%). L R - M S (EI): M ( m / z ) = 732, calcd. for C H , N Z n : 732.7718 (63.929 ( " Z n ) for Zn). +  4 8  UV-vis (CHjCh):  X  max  3  4  (nm) 420 (5.63), 534sh (3.99), 551 (4.26), 587sh (3.64). ' H N M R (CDC1 ): 3  8 2.34 (s, 12H, - C H ) , 7.75 (m, 12H, phenyl-**? 3  and.p-H), 8.06 (m, 8H, phenyl-o-H), 8.65 (s, 4 H ,  pyrr-P-H).  C r y s t a l s for X r a y c r y s t a l o g r a p h y . Z n ( T P P B r )•( M e O H )•( D M F ) . Zn(TPPBr ) (45b) 4  4  was completely dissolved in hot D M F and the solution was cooled to room temperature. The same volume of M e O H was layered on top of the porphyrin solution. After a period of 1 — 2 days shiny chip crystals were obtained. ' H N M R could not be measured in CDC1 because of the 3  low solubility of the crystals. ' H N M R (DMSO-d^: 8 2.75 (s, 3H, D M F (-CH,)), 2.89 (s, 3 H , D M F (-CHj)), 3.22 (d, 3H, M e O H  (-CH )), 4.08 (q, I H , M e O H (-OH)), 7.78 (m, 12H, phenyl-^ 3  and p-H), 7.99 (s, I H , D M F (-CHO)), 8.02 (m, 8H, phenyl-o-H), 8.60 (s, 4 H , pyrr-P-H). C H N anal.(%), calcd for C H B r N 0 Z n (45b-(MeOH)-(DMF)): C , 52.47; H , 3.21; N , 6.37, found: 4 8  3 5  4  5  2  52.32; H , 3.17; N , 6.02.  Zn(TPP(CF ) )(EtOH) . Zn(TPP(CF ) ) (48b) 3 4  3  3  4  was dissolved  in C H C l / E t O H 3  (50/50 (v/v)) at room temperature. After period of two weeks, purple prism crystals were obtained by slow evaporation of the solvents at room temperature. H N M R ( C D C y : 8 0:34 (t, 3H, E t O H (-OH)), 0.73 (t, 9 H , E t O H (-CH,)), 2.94 (m, 6H, E t O H (-CH -)), 7.70 (m, 12H, 2  19  phenyl-*? and p-H), 8.08 (m, 8H, phenyl-o-H), 8.37 (s, 4H, pyrr-p-H). CFC1 ) -48.36. UV-vis ( C H C y X 3  2  max  F N M R (CDC1 ): 8 (vs. 3  (nm) (log e): 444(5.42), 598sh (3.82), 664(4.34). C H N  219  anal.(%), calcd for C H F N Z n 0 (48b-(EtOH)), C , 59.60; H , 3.89; N , 5.15, found: C , 60.00; 5 4  4 2  1 2  4  3  3  H , 3.64; N , 5.02.  Z n ( T P P ( C H ) ) ( T H F ) ( C H C l ) . 34  6 1  34 0  ZnCTPP(CH ) ) (59b) 3  4  was  dissolved i n  C H C 1 / T H F (50/50 (v/v)) at room temperature. After a period of a week, red needle crystals 3  were obtained by slow evaporation of the solvents at room temperature. *H N M R (CDjCL): 5 I. 76 (m, T H F ) , 2,37 (s, H 0 ) , 3.56 (m, T H F ) , 7.32 (s, CHC1 ), 7.75 (m, 12H, phenyl-/* and p-H), 2  3  8.06 (m, 8H, phenyl-o-H), 8.65 (s, 4 H , pyrr-p-H). C H N anal.(%), calcd for C  5 4 8  H  4 9  2  C1 N 0, Zn  (59b-(THF) -(CHCl ) ), C , 73.35; H , 5.53; N , 6.24, found: C , 73.15; H , 5.60; N , 6.06. 16  3 04  1 2  4  6  220  R E F E R E N C E S 1) Nomenclature of tetrapyrroles; Recommendations of I U P A C - I U B Joint Commision on Biochemical Nomenclature Eur. J. Chem. 1988, 178, 277. 2) Bonnett, R. 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UV-visible spectra of freebase porphyrins, H T P P ( C F ) 2  3  4  (48a)  and H T P P ( C H ) ( 5 9 a ) in C H C 1 and their diacids in C H C 1 containing 2  3  4  2  2  2  2  0.5 %(v) T F A . The Q bands are shown in five times magnification.  234  B. Crystallographic Data Table B-l-a. Atomic coordinates and B„forZn(TPP(CF ) )-(EtOH) atom X z y K 3  Zn© F(l)  F(2) F(3) F(4) F(5) F(6) F(7) F(8) F(9) F(10) F(ll) F(12) 0(1) 0(2) 0(3) N©  N(2) N(3) N(4) C©  C(2) C(3) C(4) C(5) C(6) C(7)  C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18)  0.40652(4) -0.0024(2) 0.1343(2) 0.0886(2) 0.0857(2) 0.2337(2) 0.2514(2) 0.5928(2) 0.6770(2) 0.4803(2) 0.3258(3) 0.4561(2) 0.5179(2) 0.2500(3) 0.1471(4) -0.0946(6) 0.3575(3) 0.5318(3) 0.4884(2) 0.3399(2) 0.2669(3) 0.2081(3) 0.2633(3) 0.3642(3) 0.4671(3) 0.5511(3) 0.6700(3) 0.7205(3) 0.6330(3) 0.6454(3) 0.5600(3) 0.5460(3) 0.4765(3) 0.4393(3) 0.3732(3) 0.3394(3) 0.2878(3) 0.2550(3)  0.45182(3) 0.6348(2) 0.7873(2) 0.7600(2) 0.6128(2) 0.7615(2) 0.6072(2) 0.1348(2) 0.0913(2) 0.0155(2) 0.0129(2) 0.1002(2) 0.0247(2) 0.3304(2) 0.1289(3) . 0.0432(6) 0.5874(2) 0.4892(2) 0.3448(2) 0.4618(2) 0.6174(3) 0.6642(3) 0.6573(3) 0.6183(3) 0.6248(3) 0.5719(3) 0.5931(3) 0.5242(3) 0.4561(3) 0.3656(3) 0.3027(3) 0.1964(3) 0.1810(3) 0.2754(3) 0.3039(3) 0.3954(3) 0.4319(3) 0.5155(3)  4  0.27515(2) 0.17616(14) 0.25687(13) 0.12336(12) 0.01207(12) 0.02916(12) -0.00580(1) 0.19573(11) 0.31178(13) 0.23892(13) 0.35462(14) 0.48003(12) 0.39364(15) 0.17867(15) 0.1850(2) 0.1786(5) 0.24406(15) 0.21806(15) 0.33033(15) 0.36900(14) 0.2632(2) 0.1953(2) 0.1361(2) 0.1702(2) 0.1460(2) 0.1758(2) 0.1655(2) 0.1999(2) 0.2308(2) 0.2631(2) 0.2980(2) 0.3140(2) 0.3648(2) 0.3749(2) 0.4245(2) 0.4261(2) 0.4858(2) 0.4642(2)  3  2.105(9) 5.05(7) 4.76(7) 4.59(7) 4.21(6) 4.45(6) 3.80(6) 4.27(6) 4.28(6) 4.55(6) 5.28(7) 4.25(6) 5.72(8) 3.47(7) 8.52(12) 17.6(3) 2.20(7) 2.16(7) 1.86(6) 2.04(6) 2.13(8) 2.40(8) 2.47(8) 2.11(8) 2.15(8) 2.13(8) 2.78(9) 2.88(9) 2.20(8)  2.25(8) 2.04(8) 2.22(8) 2.18(8) 1.96(8) 1.78(7) 2.01(8) 2.49(8) 2.77(9) (continued)  235  Table B-l-a (continued) atom  X  y  z  C(19)  0.2818(3)  0.5319(3)  0.3870(2)  2.06(8)  C(20)  0.2427(3)  0.6006(3)  0.3387(2)  2.18(8)  C(21)  0.1079(4)  0.7096(3)  0.1883(2)  3.27(10)  C(22)  0.2101(4)  0.6614(3)  0.0437(2)  3.26(10)  C(23)  0.5764(4)  0.1102(3)  0.2673(2)  3.07(10)  C(24)  0.4430(4)  0.0796(3)  0.3977(2)  3.16(10)  C(25) C(26) C(27)  0.4989(3) 0.5115(3) 0.5424(4) 0.5577(4)  0.7049(3) 0.8111(3) 0.8870(3)  0.0941(2) 0.1200(2) 0.0731(2)  0.8543(3)  -0.0023(2)  2.24(8) 2.75(9) 3.45(10) 3.35(10)  0.5462(4) 0.5171(3) 0.7586(3)  0.7497(3) 0.6737(3)  -0.0297(2) 0.0178(2)  3.12(10) 2.69(9)  0.3389(3)  0.2678(2)  2.41(8)  0.7922(4)  0.3252(3)  0.1960(2)  0.9020(4) 0.9799(4)  0.3082(4) 0.3025(4)  0.2033(2) 0.2804(3)  3.37(10) 4.34(12) 4.26(12)  0.9455(4) 0.8361(3)  0.3125(3) 0.3308(3) 0.2326(3)  0.3518(2) 0.3448(2)  C(28) C(29) C(30) C(31) C(32) C(33) C(34) C(35) C(36)  3.42(10) 2.64(9) 2.22(8)  C(37) C(38) C(39)  0.3268(3) 0.2116(3)  C(40)  0.2295(5)  C(41)  0.3432(5) 0.3923(4)  0.1917(4)  0.5784(3) 0.6161(2)  0.2548(3)  0.5662(2)  3.48(10)  C(44)  0.1717(3) 0.0479(4)  0.6601(3) 0.6083(3)  0.3729(2) 0.3607(2)  2.49(9) 3.37(10)  C(45)  -0.0117(4)  0.6642(4)  0.3981(3)  C(46) C(47)  0.0512(5) 0.1739(5)  0.7673(5)  4.57(13) 5.19(15)  0.8170(4)  0.4467(3) 0.4596(2)  C(48)  0.2353(4)  0.7654(3)  0.4231(2)  3.76(10)  C(49)  0.1611(3)  C(50)  0.2063(4)  0.3458(3) 0.3502(4)  0.1053(2) 0.0323(2)  317(9) 4.58(12)  C(51)  0.1920(10)  0.0529(7)  0.1521(5)  13.4(3)  C(52)  0.1820(14)  0.0259(12)  0.0790(8)  21.2(7)  C(53)  -0.1280(8) -0.0855(10)  -0.0194(10)  0.2344(6) 0.2312(7)  14.0(4) 16.8(4)  0.1627(4)  C(42) C(43)  C(54)  0.4786(2) 0.4429(2)  0.1517(3) 0.0876(3) 0.1089(4)  2.85(9) 4.26(12)  0.4918(3)  .-0.1019(7)  4.91(14) 4.70(13)  5.00(13)  Equivalent temperature factor:  B  = 3 7t (U„(aa*) + 2  tq  2  U (bb*) + U (cc*) + 2  22  z  33  2(7 aa*bb*cosY + 2L/ aa*cc*cos|3 + 12  2L/ bb*cc*cosa) [Refer to the end of Table B-3-b for the parameters.] 23  13  236  Table B-l-b. A n i s o t r o p i c displacement parameters for Z n ( T P P ( C F ) ) ' ( E t O H ) . 3  atom  U  Zn©  F(3) F(4) F(5)  0.0361(3) 0.0400(15) 0.090(2) 0.076(2) 0.0395(15) 0.073(2)  F(6) F(7) F(8) F(9) F(10) F(ll)  0.0579(15) 0.105(2) 0.077(2) 0.077(2) 0.079(2) 0.083(2)  F(12) O(l)  0.127(2) 0.045(2) 0.113(3) 0.203(7) 0.042(2) 0.040(2) 0.029(2) 0.036(2) 0.031(2) 0.038(2) 0.041(2) 0.042(2) 0.034(2) 0.036(2)  F© F(2)  0(2) 0(3) N(l)  N(2) N(3) N(4) C© C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21)  C(22) C(23) C(24)  0.0268(2) 0.088(2) 0.070(2) 0.087(2) 0.080(2) 0.067(2) 0.067(2) 0.0460(15) 0.057(2) 0.0292(14) 0.0362(15) 0.065(2) 0.066(2) 0.039(2) 0.045(3) 0.207(7) 0.028(2) 0.026(2) 0.024(2) 0.027(2) 0.027(2) 0.036(2) 0.036(2) 0.021(2) 0.024(2) 0.028(2)  u„  U  u  0.0155(2) 0.0266(15) 0.062(2) 0.062(2)  0.0156(2) 0.0281(13)  0.0129(2) 0.0414(15) 0.0210(12)  0.0524(13) 0.0386(12) 0.0491(13) 0.0270(10) 0.0390(11) 0.0610(14) 0.0729(15) 0.074(2) 0.0502(13) 0.099(2) 0.0336(14) 0.129(3) 0.317(8) 0.0274(14) 0.0287(14) 0.0267(14) 0.0245(14) 0.029(2) 0.032(2) 0.026(2) 0.025(2) 0.027(2) 0.027(2)  0.0219(14) 0.0390(14) 0.0314(13) 0.0425(14) 0.0496(14) 0.0187(14) 0.0003(15) 0.0473(15) 0.075(2) 0.0048(15) 0.002(2) 0.089(6) 0.0200(15) 0.0202(15) 0.0136(14) 0.0192(15) 0.015(2) 0.023(2) 0.020(2) 0.015(2) 0.012(2) 0.015(2)  i3  0.0283(14) 0.0358(13) 0.0074(11) 0.0249(13) 0.0150(11) 0.0449(13) 0.0385(14) 0.0379(15) 0.031(2) 0.0420(13) 0.084(2) 0.0036(13) 0.018(3) 0.121(6)  0.043(2) 0.046(2)  0.015(2) 0.023(2)  0.0206(14) 0.0176(14) 0.0154(13) 0.0143(14) 0.012(2) 0.018(2) 0.015(2) 0.015(2) 0.012(2) 0.017(2) 0.025(2) 0.023(2)  0.024(2) 0.028(2)  0.014(2) 0.017(2)  0.013(2) 0.016(2)  0.023(2) 0.032(2) 0.027(2) 0.021(2) 0.022(2) 0.022(2)  0.017(2) 0.019(2) 0.016(2) 0.011(2) 0.011(2) 0.009(2)  0.012(2) 0.018(2) 0.012(2) 0.012(2)  0.028(2)  0.031(2) 0.023(2) 0.027(2) 0.022(2) 0.023(2) 0.027(2)  0.038(2) 0.053(3) 0.031(2) 0.035(2)  0.038(2) 0.036(2) 0.023(2) 0.025(2)  0.028(2) 0.028(2)  0.019(2) 0.023(2) 0.009(2) 0.015(2)  0.055(3) 0.039(3) 0.056(3) 0.057(3)  0.052(3) 0.051(3) 0.033(3) 0.033(3)  0.023(2) 0.029(2) 0.034(2) 0.039(2) 0.039(2) 0.051(2)  0.016(2) 0.022(2) 0.011(2) 0.016(2)  0.033(2) 0.021(2) 0.022(2) 0.027(2)  0.020(2) 0.013(2) 0.023(2) 0.033(2)  0.037(2) 0.031(2) 0.035(2) 0.036(2) 0.031(2) 0.040(2) 0.036(2) 0.035(2) 0.027(2)  0.038(2) 0.050(3) 0.030(2) 0.030(2)  3  0.0254(2) 0.078(2) 0.0491(13)  3 3  n  4  rj  0.0096(15) 0.011(2)  a  0.0464(13) 0.0246(12) 0.0416(12) 0.0170(10) 0.0198(10) 0.0281(12) 0.0077(12) 0.0186(13) 0.0448(12) 0.064(2) 0.0121(12) 0.028(2) 0.160(7) 0.0155(12) 0.0162(13) 0.0159(12) 0.0152(12) 0.0121(15) 0.021(2) 0.018(2) 0.0133(15) 0.0134(15) 0.0148(15) 0.024(2) 0.030(2) 0.0135(15) 0.0138(15) 0.0133(15) 0.0129(15) 0.0174(15) 0.0137(14) 0.0124(14) 0.0098(15) 0.013(2) 0.011(2) 0.0040(14) 0.0108(15) 0.022(2) 0.022(2) 0.016(2) 0.021(2) (continued)  237  Table B-l-b. (continued) atom C(25) C(26) C(27) C(28) C(29) C(30) C(31) C(32) C(33) C(34) C(35) C(36) C(37) C(38) C(39) C(40) C(41) C(42) C(43) C(44) C(45) C(46) C(47) C(48) C(49) C(50) C(51) C(52) C(53) C(54)  rj 0.025(2)  u  a  0.034(2) 0.055(3)  0.031(2) 0.028(2) 0.030(2)  0.070(3)  0.034(2) 0.044(2) 0.039(2) 0.035(2) 0.031(2)  0.038(3) 0.043(3) 0.030(2) 0.034(2) 0.069(3) 0.089(4) 0.076(3) 0.047(3) 0.037(2) 0.030(2) 0.033(2) 0.040(3) 0.055(3) 0.058(3) 0.035(2)  0.064(3) 0.055(3) 0.054(3) 0.038(2) 0.055(3) 0.067(3) 0.056(3) 0.049(3) 0.036(2) 0.035(2) 0.038(2) 0.056(3) 0.102(4) 0.101(4) 0.064(3) 0.047(3) 0.048(3) 0.074(3) 0.114(5) 0.099(4) 0.064(3) 0.034(2)  L7  u„  u  0.016(2) 0.024(2)  0.010(2) 0.020(2) 0.025(2) 0.024(2) 0.025(2) 0.023(2)  0.0150(15) 0.015(2)  0.015(2) 0.036(3)  0.019(2) 0.025(2) 0.044(3) 0.041(3) 0.017(2) 0.017(2) 0.019(2) 0.018(2) 0.050(3) 0.072(3) 0.038(3) 0.015(2) 0.018(2) 0.029(2) 0.043(3) 0.050(3) 0.019(3) 0.015(2) 0.007(2) 0.022(2)  0.018(2) 0.029(2) 0.041(2) 0.040(3) 0.027(2) 0.018(2) 0.018(2) 0.017(2) 0.033(2) 0.045(3) 0.028(2) 0.016(2) 0.016(2) 0.024(2) 0.038(3) 0.038(3) 0.003(2) 0.007(2) 0.008(2) 0.021(2)  -0.021(6) 0.29(2)  0.017(6)  0.115(7) 0.199(11)  0.114(8) 0.074(8)  12  33  0.027(2) 0.024(2)  0.031(2) 0.030(2)  0.025(2) 0.024(2) 0.019(2) 0.042(2)  0.052(3) 0.068(3) 0.046(2) 0.035(2) 0.032(2) 0.043(2) 0.090(3) 0.076(3) 0.038(2) 0.031(2)  0.054(3) 0.049(3) 0.028(2) 0.017(2) 0.017(2) 0.014(2) 0.020(2) 0.041(3) 0.034(3) 0.013(2)  0.027(2) 0.050(2) 0.064(3)  0.024(2) 0.029(2) 0.047(3)  0.048(3) 0.045(3) 0.042(2) 0.039(2) 0.037(2) 0.119(6)  0.087(4) 0.051(3) 0.028(2)  0.072(3) 0.243(11)  0.033(2) 0.051(3) 0.071(4) 0.093(4) 0.056(3) 0.041(3) 0.043(3) 0.076(4) 0.110(7)  0.46(2)  0.32(2)  0.280(12)  0.109(8) 0.28(2)  0.166(9) 0.287(13)  0.228(12) 0.110(7)  0.193(8) 0.363(13)  0.070(8) 0.146(9)  a  0.020(2) 0.028(2) 0.021(2) 0.015(2)  0.229(14)  The general temperature factor expression:  exp(-27l (a* £V + b* U k + c* Uj 2  2  2  2  2  22  2  + 2a*b*[/ M + 2a*c*[/ />/ + 2b*c*U >fe/  [Refer to the end of Table B-3-b for parameters.]  12  13  23  238  T a b l e B-2-a. Atomic coordinates and B„ for Zn(TPPBr )-(MeOH>pMF) 4  atom Br© Br(2) Br(3) Br(4) Zn® O(l) 0(2) N© N(2) N(3) N(4) N(5) C© C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(30) C(31) C(32)  x 0.58180(4) 0.53182(4) 0.72294(5) 0.68507(4) 0.74243(3) 0.9292(2) 0.9950(3) 0.6918(2) 0.7148(2) 0.7404(3) 0.7244(3) 1.0279(3) 0.6800(3) 0.6312(3) 0.6151(3) 0.6568(3) 0.6689(3) 0.6999(3) 0.7228(3) 0.7493(3) 0.7437(3) 0.7598(3) 0.7470(3) 0.7347(3) 0.7220(3) 0.7313(3) 0.7386(3) 0.7412(3) 0.7598(4) 0.7536(3) 0.7291(3) 0.7082(3) 0.6585(3) 0.7444(3) 0.7353(4) 0.6404(4) 0.5561(3) 0.5650(3) 0.7910(3) 0.7039(4) 0.7328(4) 0.8487(5) 0.9364(4) 0.9075(4)  y_  z  ff  -0.04914(3) -0.28795(3) -0.43406(3) -0.17764(3) -0.26443(3) -0.3092(2) -0.4945(3) -0.2356(2) -0.4077(2) -0.2803(2) -0.1109(2) -0.6695(3) -0.1434(2) -0.1512(2) -0.2480(3) -0.3030(2) -0.4089(2) -0.4559(2) -0.5660(2) -0.5831(2) -0.4831(2) -0.4684(2)  0.69092(3) 0.74241(3) -0.07081(3) -0.11018(3) 0.29861(3) 0.2706(2) 0.3487(3) 0.4507(2) 0.3328(2) 0.1550(2) 0.2710(2) 0.3602(3) 0.4904(2) 0.5963(2) 0.6173(2) 0.5260(2) 0.5139(2) 0.4234(2) 0.4117(3) 0.3158(3) 0.2656(2) 0.1650(3) 0.1150(2) 0.0177(3) 0.0008(3) 0.0852(2) 0.0951(3) 0.1808(3) 0.1855(3) 0.2790(3) 0.3331(3) 0.4349(2) 0.6026(2)  1.875(8) 2.238(8) 3.16(1) 2.351(9) 0.925(7) 1.84(5) 4.26(9) 0.97(5) 0.99(5) 1.13(6) 1.05(5) 3.14(9) 0.98(6) 1.11(6) 1.15(6) 0.84(6) 0.99(6) 0.95(6) 1.25(7) 1.35(7) 0.97(6) 1.28(7) 1.21(7) 1.61(7) 1.52(7) 1.12(6) 1.28(7) 1.25(7) 1.78(8) 1.52(7) 1.19(7) 1.05(6) 0.94(6) 1.35(7) 1.81(8) 1.75(7) 1.67(7) 1.25(7) 1.40(7) 2.23(8) • 2.81(9) 3.1(1) 2.92(9) 2.10(8)  -0.3717(3) -0.3479(3) -0.2456(3) -0.2030(3) -0.1024(2) -0.0631(2) 0.0378(3) 0.0495(3) -0.0423(2) -0.0561(2) -0.4795(2) -0.4985(3) -0.5599(3) -0.6046(3) -0.5885(3) -0.5263(3) -0.5649(3) -0.6128(3) -0.7001(3) -0.7402(3) -0.6944(3) -0.6062(3)  0.6507(3) 0.7349(3) 0.7719(3) 0.7234(3) 0.6385(3) 0.1069(3) 0.1091(3) 0.0536(3) -0.0030(3) -0.0061(3) 0.0505(3)  eq  (continued)  239 Table B-2-a. (continued)  atom C(33) C(34) C(35) C(36) C(37) C(38) C(39) C(40) C(41) C(42) C(43) C(44) C(45) C(46) C(47) C(48)  X  y  0.7473(4) 0.8540(4) 0.8596(5) 0.7586(6) 0.6541(5) 0.6477(4) 0.7183(3) 0.6320(3) 0.6417(4) 0.7399(4) 0.8271(4) 0.8170(3) 0.9928(4) 1.0115(4) 1.0232(4) 1.0378(6)  -0.0301(3) -0.0412(3) 0.0228(3) 0.0984(4) 0.1117(3) 0.0485(3) . 0.0311(2) 0.1252(3) 0.2044(3) 0.1913(3) 0.0987(3) 0.0178(3) -0.2383(3) -0.5789(4) -0.6752(4) -0.7651(5)  z 0.0077(3) -0.0688(3) -0.1512(3) -0.1574(3) -0.0823(4) 0.0021(3) 0.4860(2) 0.5007(3) 0.5494(3) 0.5816(3) 0.5663(3) 0.5185(3) 0.2765(4) 0.3124(4) 0.4616(4) 0.3164(5)  1.64(7) 2.36(9) 3.0(1) 3.7(1) 3.2(1) 2.44(9) 1.12(6) 1.62(7) 1.83(8) 1.89(8) 1.99(8) 1.56(7) 3.2(1) 3.5(1) 3.6(1) 5.6(2)  Equivalent temperature factor: g B  tq  =  -7t (U„(aa*) + U (bb*) + U (cc*) 2  2fJ bb*cc*cosa) 23  2  2  22  2  3)  + 2fJ12aa*bb*cosy + 2rj13aa*cc*cosp +  240  T a b l e B-2-b. Anisotropic displacement parameters for Zn(TPPBr )-(MeOH)-(DMF) atom U C7 u* U ^22 4  33  Br® Br(2)  0.0403(2) 0.0444(2)  Br(3) Br(4) Zn® O(l) 0(2) N® N(2) N(3)  0.0841(4) 0.0524(3) 0.0184(2) 0.016(1) 0.039(2) 0.016(1) 0.016(1) 0.023(2)  N(4) N(5)  0.020(1) 0.025(2)  0.0150(2) 0.0194(2) 0.0252(2) 0.0255(2) 0.0076(2) 0.018(1) 0.038(2) 0.009(1) 0.010(1) 0.010(1) 0.009(1) 0.030(2)  C(I) C(2)  0.015(2) 0.019(2) 0.016(2) 0.012(2) 0.014(2) 0.013(2) 0.019(2) 0.026(2) 0.015(2) 0.021(2) 0.019(2) 0.030(2) 0.027(2) 0.019(2) 0.022(2)  0.011(1) 0.011(1) 0.015(2) 0.012(1) 0.012(2) 0.009(1) 0.011(1) 0.008(1) 0.007(1) 0.012(2) 0.014(2) 0.019(2) 0.020(2) 0.014(2) 0.011(2)  0.023(2) 0.040(2) 0.032(2)  C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10)  C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(30) C(31) C(32)  n  13  0.0120(2) 0.0130(2)  -0.0079(2) -0.0126(2)  -0.0010(2) 0.0061(2)  0.0243(2) 0.0177(2) 0.0099(2) 0.032(2) 0.102(3) 0.011(1) 0.012(1) 0.011(1) 0.009(1) 0.053(3) 0.013(2) 0.015(2) 0.012(2) 0.008(2) 0.015(2) 0.015(2) 0.018(2) 0.015(2) 0.015(2) 0.014(2) 0.013(2) 0.015(2) 0.010(2) 0.008(2)  -0.0213(2) -0.0111(2)  -0.0284(2) -0.0198(2) -0.0047(2) -0.004(1) -0.046(2) -0.004(1) -0.004(1) -0.006(1) -0.005(1) -0.005(2)  -0.0041(1) -0.0009(1) -0.0013(2) 0.0036(2) 0.0011(1) 0.004(1) 0.035(2) 0.002(1) 0.000(1) 0.000(1) 0.000(1) 0.010(2)  -0.005(1) -0.006(1) -0.001(1) -0.004(1) -0.008(1) -0.006(1) -0.006(1) -0.005(1) -0.004(1) -0.002(1) -0.002(1) -0.007(2) -0.004(1) -0.002(1)  -0.001(1) 0.001(1) 0.001(1) 0.003(1) 0.004(1) 0.002(1) 0.003(1) 0.000(1) 0.000(1) -0.004(1) -0.004(1) -0.003(1) 0.001(1) 0.000(1)  -0.003(1) -0.004(1)  0.001(1) 0.002(1)  -0.010(2) -0.007(2)  0.005(1) 0.000(1)  -0.0046(2) -0.004(1)  0.010(1) 0.012(2) 0.011(2)  0.012(2) 0.013(2) 0.017(2) 0.016(2)  -0.023(2) -0.004(1) -0.004(1) -0.007(1) -0.002(1) -0.003(2) -0.004(1) -0.007(1) -0.006(1) -0.003(1) -0.007(1) -0.004(1) -0.005(1) -0.004(1) -0.006(1) -0.006(1) -0.007(1) -0.009(2) -0.008(2) -0.004(1) -0.002(1) -0.003(1) -0.008(2) -0.008(2)  0.024(2) 0.017(2)  0.008(1) 0.008(1)  0.016(2) 0.015(2)  -0.005(1) -0.001(1)  -0.009(1) -0.006(1)  0.000(1) -0.001(1)  0.017(2) 0.019(2) 0.032(2) 0.038(2)  0.008(1) 0.016(2) 0.020(2) 0.014(2)  0.009(2) 0.018(2) 0.018(2) 0.007(2)  -0.001(1) -0.004(1) 0.002(2) -0.001(2)  -0.003(1) -0.009(1) -0.015(2)  -0.001(1) 0.000(1)  0.026(2) 0.017(2)  0.014(2) 0.013(2)  -0.008(2) -0.002(1)  0.028(2) 0.037(2) 0.054(3) 0.071(3) 0.040(3) 0.029(2)  0.010(1) 0.024(2) 0.027(2) 0.019(2)  0.021(2) 0.018(2) 0.012(2)  0.028(2) 0.024(2)  -0.003(2) -0.002(2)  0.019(2) 0.025(2) 0.021(2)  -0.006(2) -0.017(2) -0.026(2) -0.011(2)  -0.008(1) -0.002(1) 0.007(2) 0.004(2) -0.001(2)  0.029(2) 0.022(2)  0.004(2) -0.006(2)  0.001(2) 0.000(2)  -0.002(1) 0.002(1) 0.004(1) -0.001(1) -0.001(1) -0.009(2) -0.009(2) -0.009(2) -0.012(2) -0.006(2) (continued)  241  Table B-2-b, (continues) atom C(33) C(34) C(35) C(36) C(37) C(38) C(39) C(40) C(41) C(42) C(43) C(44) C(45) C(46) C(47) C(48)  0.043(2) 0.041(2) 0.067(3) 0.103(5) 0.069(3) 0.047(3) 0.022(2) 0.029(2) 0.036(2) 0.037(2) 0.027(2) 0.019(2) 0.031(2) 0.027(2) 0.035(3) 0.072(4)  U -0.010(2) -0.011(2) -0.026(2) n  0.013(2) 0.026(2) 0.033(2) 0.028(2) 0.022(2) 0.021(2) 0.013(1) 0.015(2) 0.009(2) 0.019(2) 0.031(2) 0.019(2) 0.030(2) 0.049(3) 0.039(3) 0.049(3)  0.008(2) 0.022(2) 0.016(2) 0.022(2) 0.032(3) 0.023(2) 0.010(2) 0.021(2) 0.023(2) 0.022(2) 0.025(2) 0.021(2) 0.067(4) 0.063(4) 0.056(3) 0.072(5)  -0.028(3) -0.005(2) -0.003(2) -0.007(1) -0.008(2) -0.004(2) -0.015(2) -0.012(2) -0.002(2) -0.014(2) -0.017(2) -0.008(2) -0.006(3)  rj  ^23  13  -0.009(2) -0.007(2) -0.003(2) -0.028(3) -0.029(3) -0.014(2) -0.004(1) -0.011(2) -0.009(2) -0.010(2) -0.013(2) -0.008(2) -0.018(2) -0.023(2) -0.014(2) -0.004(4)  0.003(1) 0.000(2) 0.003(2) 0.012(2) 0.010(2) 0.002(2) 0.001(1) 0.001(1) -0.003(1) -0.004(1) -0.003(2) 0.000(1) 0.001(2) 0.027(3) 0.024(2) -0.010(3)  The general temperature factor expression:  e x p ^ T i ^ a * ^ / + b* U k 2  2  2  2  22  + c* U / 2  3  + 2a*b*t/ M + 2a*c*rj /,/+ 2b*c*L7 /fe/ 12  13  23  242  T a b l e B-3-a. Atomic coordinates and B„ for Zn(TPP(CH ) )-(THF) -(CHCl ), 3  atom  X  y  Zn© CI© Cl(2) Cl(3)  0.26812(5) 0.1904(4) 0.2592(4) 0.3791(7) 0.2693(4) 0.2858(7)  0.12829(4) 0.0949(3) 0.2290(3) 0.1530(5) 0.2483(2)  4  16  z  0.1361(4) 0.1338(4) 0.0496(4) 0.0462(4)  0.0902(5) 0.1139(3) 0.1180(3) 0.1145(3) 0.1155(3) 0.1004(3) 0.0816(3) 0.0900(3) 0.1099(3) 0.1254(4) 0.1300(4)  C(15) C(16)  -0.0423(4) -0.0170(4) 0.0874(4) 0.1415(4) 0.2443(4) 0.3009(5) 0.3983(4) 0.4021(4) 0.4875(4) 0.4898(4)  0.1432(4) 0.1370(4) 0.1209(4) 0.1099(3) 0.1001(3) 0.0792(3) 0.0868(3) 0.1093(3) 0.1221(3) 0.1239(4)  0.87154(5) 0.3699(3) 0.4358(4) 0.3397(5) 0.8706(3) 0.3694(6) 0.7589(3) 0.8938(3) 0.9843(3) 0.8494(3) 0.7035(3) 0.6346(4) 0.6487(4) 0.7262(3) 0.7663(3) 0.8431(3) 0.8827(3) 0.9550(3) 0.9633(3) 1.0302(3) 1.0393(3) 1.1077(4) 1.0936(3) 1.0166(3) 0.9763(3) 0.9004(3)  C(17) C(18)  0.5789(4) 0.5542(4)  0.1321(4)  0.8613(3)  1.6(1)  C(19) C(20) C(21)  0.4468(4) 0.3938(4)  0.1272(4) 0.1167(4) 0.1069(3)  0.7875(3) 0.7801(3) 0.7125(3)  0.2714(5) 0.0455(5)  0.0547(4) 0.0720(4)  0.5623(4) 0.5890(4)  1.6(1) 1.3(1) 1.4(1) 2.2(2) 2.2(2)  0.2626(5) 0.4834(5) -0.0471(4)  1.1761(4) 1.1484(4) 0.7222(4) 0.6863(4)  2.5(2) 1.8(2)  -0.0647(5)  0.0461(4) 0.0682(4) 0.1397(4) 0.2056(4)  -0.1513(5) -0.2223(5) -0.2081(5)  0.2175(4) 0.1636(4) 0.0976(4)  0.6438(4) 0.6392(4) 0.6766(4)  0.0857(4)  C(31) C(32)  -0.1208(5) 0.0832(4) 0.0164(4)  0.7183(4) 1.0982(3) 1.1144(4)  2.7(2) 2.6(2) 2.6(2) 2.0(2)  C(33) C(34)  -0.0348(4) -0.0198(5)  0(1) 0(2) N© N(2) N(3) N(4) C© C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14)  C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(30)  0.2283(3) 0.1244(3) 0.3076(3) 0.4112(3) 0.2890(4) 0.2343(5)  0.1127(3) 0.0577(4) 0.0621(4) 0.1210(5)  1.1801(4) 1.2279(4)  1.19(1) 6.7(1) 5.2(1) 8.0(2) 2.6(1) 4.4(2) 1.3(1) 1.1(1) 1.2(1) 1.2(1) 1.1(1) 1.3(1) 1.3(1) 1.2(1) 1.2(1) 1.3(1) 1.5(1) 1.5(1) 1.3(1) 1.3(1) 1.1(1) 1.5(1) 1.2(1) 1.1(1) 1.2(1) 1.3(1)  1.3(1) 2.0(2)  1.3(1) 1.6(2) 1.8(2) 2.4(2) (continued)  3  T a b l e B-3-a. (continued) atom C(35) C(36) C(37) C(38) C(39) C(40) C(41) C(42) C(43) C(44) C(45) C(46) C(47) C(48) C(49A) C(50) C(51) C(52A) C(53) C(54) C(55) C(56) C(49B) C(52B)  X  0.0428(5) . 0.0942(4) 0.5829(4) 0.5990(4) 0.6882(5) 0.7608(4) 0.7452(5) 0.6576(4) 0.4534(4) 0.5153(4) 0.5665(4) 0.5632(5) 0.5047(5) 0.4504(4) 0.3495(8) 0.3115(6) 0.2362(6) 0.226(1) 0.166(1) 0.255(2) 0.320(2) 0.249(3) 0.314(2) 0.186(1)  y  z  0.1770(4) 0.1731(4) 0.1344(4) 0.1982(4) 0.2116(4) 0.1581(4) 0.0937(4) 0.0812(4) 0.1069(3) 0.0479(4) 0.0476(4) 0.1059(5) 0.1660(4) 0.1663(4) 0.2900(6) 0.3694(5) 0.3695(5) 0.292(1) 0.1741(9) 0.220(1) 0.162(1) 0.185(2) 0.288(2) 0.2938(8)  1.2097(4) 1.1463(4) 1.0205(3) 1.0577(4) 1.0990(4) 1.1019(4) 1.0639(4) 1.0220(4) 0.6453(3) 0.6294(4) 0.5668(4) 0.5197(4) 0.5340(4) 0.5973(4) 0.9008(7) 0.9017(4) 0.8364(5) 0.813(1) 0.4080(8) 0.378(2) 0.360(1) 0.354(2) 0.925(2) 0.8415(9)  2.3(2) 2.0(2) 1.2(1) 1.7(1) 2.5(2) 2.4(2) 2.2(2) 1.8(2) 1.1(1) 1.7(1) 2.1(2) 2.3(2) 2.2(2) 1.7(1) 0.6(2) 3.6(2) 3.7(2) 3.8(4) 4.3(3) 8.6(5) 5.8(4) 7.5(6) 7.5(6) 2.4(3)  Equivalent temperature factor:  B = 3 7 i ( U „ ( a a * ) + U (bb*) + U (cc*) + 2L7 aa*bb*cosy + 2C7 aa*cc*cosP + 2  tq  ,bb*cc*cosa)  2  2  22  2  33  12  13  244  T a b l e B-3-b. Anisotropic displacement parameters for Zn(TPP(CH ) )'(THF) /(CHCi ), 3  atom  ^33  Zn© O(l)  0.0077(3) 0.031(2)  0.0205(4) 0.023(2)  0.0171(4) 0.042(3)  N© N(2)  0.010(3) 0.009(2)  0.018(3) 0.014(3)  N(3) N(4) C© C(2) C(3) C(4) C(5)  0.005(2) 0.016(3) 0.010(3) 0.013(3) 0.014(3) 0.011(3) 0.012(3) 0.014(3)  C(22)  0.008(3) 0.008(3) 0.016(3) 0.011(3) 0.012(3) 0.021(3) 0.016(3) 0.016(3) 0.010(3) 0.012(3) 0.007(3) 0.010(3) 0.008(3) 0.015(3) 0.019(4) 0.021(4)  0.022(3) 0.018(3) 0.016(3) 0.017(3) 0.019(4) 0.020(3) 0.017(4) 0.022(4) 0.013(3) 0.019(3) 0.028(4) 0.027(4) 0.016(4) 0.015(4) 0.012(3) 0.021(4) 0.015(3) 0.013(4) 0.013(3) 0.018(3) 0.025(4) 0.032(4) 0.028(4) 0.021(4) 0.039(5) 0.024(4)  C(23) C(24)  0.024(4) 0.016(4)  0.047(5) 0.019(4)  0.026(4) 0.035(4)  C(25) C(26)  0.023(4) 0.023(4)  0.017(4) 0.034(4)  C(27) C(28) C(29) C(30)  0.009(3) 0.020(4) 0.035(4) 0.019(4) 0.017(4) 0.015(4)  0.024(4) 0.036(5) 0.038(5) 0.028(4)  0.040(5) 0.041(5) 0.044(5) 0.033(5)  C(31)  0.008(3)  C(32) C(33)  0.013(3) 0.014(3) 0.020(4)  0.022(4) 0.023(4)  0.020(4) 0.025(4)  0.030(4) 0.047(5) 0.034(5) 0.025(4) 0.020(4) 0.021(4)  C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21)  C(34) C(35) C(36) C(37) C(38)  0.030(4) 0.021(4) 0.006(3) 0.017(3)  0.024(3) 0.013(3) 0.013(3) 0.018(4) 0.020(4) 0.013(3) 0.019(3)  4  1 f  3  U  u„  u  0.0000(4) 0.002(3) -0.004(2) -0.001(2) -0.001(2) -0.001(2)  0.0008(2) -0.012(2)  -0.0007(5) -0.001(3) 0.003(2) -0.001(2)  u  0.002(2) 0.003(3) 0.001(3) -0.003(2) -0.005(3) -0.001(3) -0.001(3) -0.003(3) 0.002(3) -0.001(2) 0.000(2) 0.000(3) -0.004(3) 0.002(2) 0.001(3) -0.002(3) -0.002(3) -0.002(3) 0.003(3) 0.004(3) 0.003(3)  0.004(2) -0.002(2) 0.000(2) 0.000(2) 0.002(3) 0.000(2) -0.001(3) -0.003(3) -0.003(2) 0.000(2)  23  -0.001(2) -0.002(2)  0.000(3) 0.002(2) 0.004(2) -0.001(3) 0.005(3)  0.002(3) -0.005(4) 0.003(3) 0.005(3) 0.004(3) -0.003(3) -0.003(3) 0.001(3) 0.001(3) 0.004(3) 0.001(3) -0.001(3) -0.002(3) -0.005(3) 0.002(3) -0.004(3) -0.007(3) -0.005(4) 0.002(3) 0.001(3) 0.001(3)  0.024(3) 0.007(3)  0.004(3) 0.007(4)  0.001(3) -0.003(3) 0.001(3) 0.006(3)  0.002(3) -0.002(3) -0.008(3) -0.017(3) -0.012(3)  0.010(3) 0.003(3) 0.004(3) 0.006(4) -0.004(4)  -0.005(3) -0.004(3)  -0.004(3) -0.005(3)  0.007(4) 0.015(4)  0.004(2)  -0.001(3)  0.002(3)  0.024(4) 0.027(4)  -0.002(3) 0.002(3) 0.006(3)  0.003(3) 0.004(3) 0.013(3)  0.002(3) 0.014(3) -0.004(4)  0.023(4) 0.030(4) 0.019(3) 0.026(4)  0.003(3) -0.003(3) .-0.004(3) 0.003(3)  0.001(3) 0.005(3) 0.001(2)  -0.007(3) -0.007(3) -0.002(3)  -0.001(3)  -0.004(3)  0.017(3) 0.019(4) 0.024(4) 0.016(3) 0.023(4) 0.019(4) 0.015(4) 0.016(4) 0.014(3) 0.024(4) 0.017(3) 0.028(4) 0.021(3) 0.016(3) 0.018(4) 0.026(4) 0.039(5)  0.008(3) 0.011(3) -0.001(3)  -0.002(3) 0.007(2) 0.003(3) 0.005(3) 0.003(3) 0.006(3) -0.001(3) -0.003(3) -0.001(3) -0.003(2)  (continued)  245  T a b l e B-3-b. (continued) atom  Un 0.023(4) 0.037(4) 0.020(4)  0.043(5) 0.040(5) 0.044(5)  C(42)  0.014(4) 0.021(4) 0.025(4) 0.038(5) 0.059(6) 0.037(5) 0.024(4) 0.025(4) 0.025(4)  0.033(4) 0.013(3) 0.019(4) 0.030(4) 0.012(4) 0.023(4) 0.023(4) 0.052(5) 0.071(6)  C(43)  C(44) C(45)  C(46) C(47) C(48) C(50) C(51)  u  0.021(4) 0.009(3) 0.019(3) 0.012(3) 0.017(4) 0.024(4) 0.017(3) 0.060(5) 0.047(5)  L7  fj  -0.006(3) -0.001(3) 0.006(3)  -0.007(3) -0.014(3) -0.011(3)  -0.006(4) -0.003(4) -0.001(4)  0.003(3) -0.001(2) 0.004(3) 0.002(3) -0.003(3) -0.011(3) 0.003(3) -0.008(4) 0.005(4)  -0.006(3) 0.003(3) -0.002(3) 0.000(3) 0.007(3) 0.001(3) -0.001(3) 0.021(4) 0.012(4)  -0.003(3) -0.001(3) -0.002(3) -0.007(4) -0.007(4) 0.015(4) -0.002(3) -0.006(5) 0.010(5)  rj  U C(39) 0.028(4) C(40) 0.011(3) C 0.019(4) (41  3 1  12  23  The general temperature factor expression:  exr3(-2n\a* U h z  2  u  + b^U^k + c * r j / + 2a*b*U hk + 2a*c*l7<W + 2 b * c * f J £ / 2  2  33  n  Parameters: a, b, c, a, (3, y; lattice constants (refer to Table 2-12) a*, b*, c*; reciprocal lattice parameters ^ 2  8  1 3  23  

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