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Protochemical and crystallographic studies on Dimethyl 9,10-Dihydro-9-Methyl-9,10-Ethenoanthracene-11,12-Dicarbosylate Pokkuluri, Phani Raj 1987

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PHOTOCHEMICAL AND CRYSTALLOGRAPHIC STUDIES ON DIMETHYL 9,10-DIHYDRO-9-METHYL-9,10-ETHENOANTHRACENE-11,12-DICARBOXYLATE By PHANI RAJ POKKULURI B . S c , Nagarjuna U n i v e r s i t y , I n d i a , 1982 M.Sc., Ind i a n I n s t i t u t e of Technology, Kanpur, 1984 A THESIS SUBMITTED I N PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE I N THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF CHEMISTRY) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA SEPTEMBER 1987 © PHANI RAJ POKKULURI, 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date 14 0& h i DE-6(3/81) To the wonderful memories of Praveen ABSTRACT The photochemistry of dimethyl 9,10-dihydro-9-methyl-9,10-etheno-anthracene-11,12-dicarboxylate (5) was s t u d i e d i n s o l u t i o n as w e l l as i n the s o l i d s t a t e . Upon d i r e c t i r r a d i a t i o n i n s o l u t i o n , three products were obtained, two of which were i d e n t i f i e d as r e g i o i s o m e r i c products of the di-7r-methane rearrangement ( d e r i v a t i v e s of s e m i b u l l -valene) and the other a d e r i v a t i v e of dibenzocyclooctatetraene. When s e n s i t i z e d (by acetone, xanthone or benzophenone) i n s o l u t i o n , only the di -7r-methane rearrangement products were obtained, suggesting that the other photoproduct obtained i n d i r e c t i r r a d i a t i o n might be a s i n g l e t - d e r i v e d product. In a c e t o n i t r i l e approximately 65% of the photochemical r e a c t i o n observed was di -7r-methane rearrangement. S o l i d s t a t e i r r a d i a t i o n s mainly r e s u l t e d i n di -7r-methane r e a r -rangement but w i t h a r e v e r s a l of product s e l e c t i v i t y from that observed i n s o l u t i o n . The X-ray c r y s t a l s t r u c t u r e of the s t a r t i n g m a t e r i a l i n d i c a t e s t h a t one of the e s t e r groups i s conjugated to the c e n t r a l double bond while the other i s non-conjugated. R a d i c a l s t a b i l i z a t i o n through c o n j u g a t i o n w i t h the e s t e r carbonyl group i s c o n s i s t e n t w i t h the major product formed i n the s o l i d s t a t e . A r e g u l a r decrease i n the photoproduct s e l e c t i v i t y was observed w i t h the extent of g r i n d i n g of the c r y s t a l s , and t h i s may be a t t r i b u t e d to a lower r e g i o s e l e c t i v i t y at the surface than t h a t w i t h i n the b u l k of the c r y s t a l . I r r a d i a t i o n i n a KBr matrix r e s u l t e d not only i n producing more presumed s i n g l e t product, but a l s o i n the enhancement - i v -of the rate of the reaction. Also the s i n g l e t photoproduct was found to be produced more when pressure was applied i n the s o l i d state. Thus, the photochemical re a c t i o n of 5 was found to be sensi-t i v e to the environment i n which the rea c t i o n i s taking place. I r r a d i a t i o n of a s o l i d s o l u t i o n of 1% xanthone and the s t a r t i n g material demonstrated the p o s s i b i l i t y of s o l i d - s t a t e s e n s i t i z a t i o n . The s e n s i t i z e d i r r a d i a t i o n s i n the s o l i d state were found to produce more of the presumed s i n g l e t product, and t r i p l e t - t r i p l e t a n n i h i l a t i o n was suggested as one of the possible explanations. - V -TABLE OF CONTENTS Page ABSTRACT i i i LIST OF FIGURES v i i LIST OF SCHEMES v i i i LIST OF TABLES i x ACKNOWLEDGEMENTS x INTRODUCTION 1 Topochemical P r i n c i p l e 1 Unimolecular Reactions 5 Reaction Cavity and S t e r i c Compression 8 Apparent V i o l a t i o n s of the Topochemical P r i n c i p l e . . . . 9 Dynamic Preformation . . . 10 The Di-II-Methane Rearrangement 11 M u l t i p l i c i t y and R e g i o s e l e c t i v i t y of Di-II-Methane Rearrangement 13 Di-II-Me thane Rearrangement of Dibenzobarrelenes 16 Objectives of the Present Work 23 RESULTS AND DISCUSSION 25 Synthesis of S t a r t i n g Material 26 Solution Phase Photochemsitry of Compound 5 27 Char a c t e r i s a t i o n of the Photoproducts 29 - v i -I d e n t i f i c a t i o n of S t a r t i n g M a t e r i a l and Photoproducts by Gas Chromatography 31 D i s c u s s i o n of the S o l u t i o n Photochemical R e s u l t s 33 S o l i d State Photochemistry of Compound 5 38 D i s c u s s i o n of the S o l i d State Photochemical R e s u l t s . . . 39 Influence of E l e c t r o n i c Factors i n the S o l i d State . . . . 40 Role of Packing E f f e c t s i n the C r y s t a l L a t t i c e 41 E f f e c t of Powdering the C r y s t a l s on the R e g i o s e l e c t i v i t y of the Di-II-Methane Rearrangement of 5 42 S i n g l e C r y s t a l P h o t o l y s i s 44 UV-VIS Spectrum of 5 i n the S o l i d State 49 S e n s i t i z e d P h o t o l y s i s of 5 i n the S o l i d State 51 E f f e c t of KBr M a t r i x on P h o t o l y s i s of 5 56 E f f e c t of Pressure on the P h o t o l y s i s of 5 i n the S o l i d State 57 D i s c u s s i o n of the C r y s t a l S t r u c t u r e of Compound 5 . . . . 61 D i s c u s s i o n on the Minor Disorder of the St r u c t u r e . . . . 67 EXPERIMENTAL 70 Photochemical Work 71 C r y s t a l l o g r a p h i c Work 85 REFERENCES 88 APPENDIX 94 - v i i -LIST OF FIGURES Figure Caption Page 1 Two structures possible f o r compound 6 30 2 Graph showing the e f f e c t of grinding the c r y s t a l s on the photoproduct r a t i o s 43 3 . Photograph of several s i n g l e c r y s t a l s of 5 before photolysis 47 4 Photograph of several single c r y s t a l s of 5 a f t e r photolysis 48 5 UV-VIS spectrum of 5 i n KBr p e l l e t before and a f t e r photolysis 50 6 ORTEP diagram of molecule 1 63 7 ORTEP diagram of molecule 2 63 8 Packing diagram of compound 5 64 9 Two dibenzobarrelene diesters c l o s e l y r e l a t e d to 5 64 10 Torsion angles i n v o l v i n g carbon atoms of the ce n t r a l double bond and the carbonyl groups . . . . 65 11 Two possible orientations of a carbomethoxy group separated by 180° 67 - v i i i -LIST OF SCHEMES Scheme Page 1 4 2 ; 7 3 9 4 12 5 ' 12 6 13 7 14 8 15 9 16 10 17 11 19 12 20 13 26 14 27 15 28 16 34 17 35 18 37 19 53 - ix-LIST OF TABLES Table Caption Page 1 R e g i o s e l e c t i v i t i e s of di-7r-methane rearrangement of 1 observed by Iwamura et a l . 18 2 Comparison of photoproduct r a t i o s obtained from the NMR i n t e g r a t i o n and the GC i n t e g r a t i o n 32 3 The photoproduct r a t i o s obtained i n three solvent media 36 4 The photoproduct r a t i o s obtained i n the s o l i d state 39 5 Results of sin g l e c r y s t a l photolysis of 5 45 6 Photoproduct r a t i o s obtained i n 1% (mol/mol) xanthone-sensitized i r r a d i a t i o n s . 52 7 Results showing the e f f e c t of KBr matrix and that of pressure on the photoproduct r a t i o s 57 8 Results showing the e f f e c t of pressure on the photo-product r a t i o s of 5 i n the s o l i d state 58 9 Several i r r a d i a t i o n r e s u l t s showing the e f f e c t of KBr matrix on the rate of photolysis of 5 60 10 Data c o l l e c t i o n parameters and c r y s t a l l o g r a p h i c r e s u l t s obtained 62 11 Torsion angles <f>± and <f>2 of both the molecules i n the asymmetric u n i t 66 ACKNOWLEDGEMENTS I thank my research supervisors Drs. John R. Scheffer and J . Tro t t e r f o r t h e i r encouragement and guidance into t h i s j o i n t venture, wherein I have t r i e d to lea r n a b i t of photochemistry and crystallography. I deeply appreciate the f r i e n d l y help of Miguel A. Garcia-Garibay and Fred C. Wireko throughout t h i s project. The fr i e n d s h i p of a l l the members of both the groups i s also appreciated. I thank Dr. A. G. M i t c h e l l of Faculty of Pharmaceutical Sciences f o r allowing me to use h i s grinding apparatus. F i n a l l y , I would l i k e to thank the s t a f f of the departmental NMR, MS, and Elemental analysis for t h e i r co-operation during my proj ect. -1-INTRODUCTION Photochemistry has long been a f a s c i n a t i n g branch of chemistry. Recently the study of photochemical r e a c t i o n s i n a n i s o t r o p i c media has a t t r a c t e d the a t t e n t i o n of s e v e r a l research groups a l l over the w o r l d . ^ The a n i s o t r o p i c medium w i t h which t h i s t h e s i s i s concerned i s the molecular c r y s t a l l i n e environment. An attempt i s made here to introduce b r i e f l y the t o p i c of s o l i d s t a t e photochemistry. Ref-erence 1 l i s t s some of the a r t i c l e s t hat review the present day i n -depth understanding of the f i e l d . Topochemical P r i n c i p l e Research i n the e a r l y 1900's i n the f i e l d of s o l i d s t a t e organic chemistry l e d to an important concept or p r i n c i p l e of l e a s t motion. The p r i n c i p l e , known as the "topochemical p r i n c i p l e " put forward by K o h l s c h u t t e r ^ i n 1918, s t a t e s that a l l chemical r e a c t i o n s i n the s o l i d s t a t e tend to occur w i t h a minimum of atomic and molecular movement. In other words, the r e a c t i o n pathway r e q u i r i n g l e a s t motion of the r e a c t a n t ( s ) w i l l be p r e f e r r e d to those which r e q u i r e greater motion. Thus, the e f f e c t of the c r y s t a l l a t t i c e i s to some-what r e s t r i c t the motions necessary f o r the r e a c t i o n . The r e a c t i o n o c c u r r i n g under such c o n t r o l i s s a i d to be topochemically c o n t r o l l e d . The topochemical p r i n c i p l e , despite the number of apparent v i o l a t i o n s r e p o r t e d ( e x e m p l i f i e d l a t e r ) , i s s t i l l considered v a l i d i n the f i e l d o s o l i d s t a t e organic chemistry. Schmidt and h i s c o l l a b o r a t o r s are c r e d i t e d w i t h being pioneers i n -3-the systematic study of photochemical reactions i n the c r y s t a l l i n e phase. They used X-ray crystallography as a t o o l to examine the s t r u c t u r a l parameters of the s o l i d state. Their work i n the e a r l y 1960's on the photodimerization of a number of cinnamic acids i n the s o l i d state (which i n s o l u t i o n undergo t r a n s - c i s isomerization) y i e l d e d very i n t e r e s t i n g r e s u l t s which not only confirmed the topo-chemical p r i n c i p l e of Kohlschutter but also gave a better i n s i g h t into photoinduced chemical reactions i n the s o l i d s t a t e . ^ " ^ Based on these photochemical and c r y s t a l l o g r a p h i c studies, Schmidt deduced that the packing arrangement i n the c r y s t a l l a t t i c e plays a dominant r o l e i n determining the course of s o l i d state reactions. In other words, the separation distance and the o r i e n t a t i o n of the reacting f u n c t i o n a l groups with respect to one another are more important than the r e a c t i v i t y of the molecules themselves. Since the pioneering studies by Schmidt, several [2+2] photodimerization reactions were studied i n the s o l i d state, and the s t r u c t u r a l char-a c t e r i s t i c s of the products formed were explained on the basis of the c r y s t a l structures of the s t a r t i n g materials. A few examples selected at random are shown i n Scheme 1. -4--COO" d — term Ooutit bond M P O ' o t ' o n ].( . < I'A K t c ' t » 1 iwijfcfcour r t lot 'on, C » M ' i c P h Ph COO" Cf-TRUXILLIC ACID P" COOK hl>. Ph COOM w Ph y3— form I ) t - 4 t*A, Tron»lotior< I I C O C X COOM P-TRUXINIC ACID f - t e ' m (4 7 - 5 1 ' A ; Tromlotion ) - * • NO REACTION Scheme 1 -5-Unimolecular Reactions Most of the i n i t i a l a c t i v i t y i n the f i e l d of s o l i d s t a t e photochemis-t r y was concerned w i t h b i m o l e c u l a r [2+2] p h o t o d i m e r i z a t i o n s . E a r l y systematic s t u d i e s y i e l d e d s t r u c t u r e - r e a c t i v i t y r e l a t i o n s h i p s which showed the i n t e r m o l e c u l a r packing of the c r y s t a l l a t t i c e to be the key f a c t o r , but gave l i t t l e i n f o r m a t i o n regarding the r e a c t i v i t y r e l a t e d to the conformation of the molecules i n the s o l i d s t a t e . Here l i e s the importance of studying unimolecular r e a c t i o n s i n the s o l i d s t a t e , as the r e a c t i v i t y mainly depends on the conformation i n t o which the molecules are locked i n the c r y s t a l l a t t i c e . I t i s known tha t organic compounds c r y s t a l l i z e u s u a l l y i n one (the lowest energy) conformation.^ The conformational f l e x i b i l i t y a v a i l a b l e i n the s o l u t i o n phase i s not p o s s i b l e i n the s o l i d s t a t e . Thus, the conformational dependence of the r e a c t i v i t y can be deduced through a systematic study of unimolecular r e a c t i o n s i n the s o l i d s t a t e . With these ideas, S c h e f f e r , T r o t t e r and co-workers s t a r t e d a systematic i n v e s t i g a t i o n of unimolecular r e a c t i o n s i n the c r y s t a l l i n e medium. With the help of X-ray c r y s t a l s t r u c t u r e data, they have ex p l a i n e d the photobehavior of a number of tetrahydronaphthoquinones and q u i n o l s i n the s o l i d state.7-14 They have a l s o s t u d i e d the s o l i d s t a t e photochemistry of a s e r i e s of a - c y c l o a l k y l - p - s u b s t i t u t e d acetophenones 1 c 1 C. and have drawn s t r u c t u r e - r e a c t i v i t y c o r r e l a t i o n s . J > T h e s e s t u d i e s were mainly concerned w i t h i n t r a m o l e c u l a r hydrogen a b s t r a c t i o n s by e i t h e r enone double bonds or carbonyl oxygens, and the geometrical parameters required f o r ab s t r a c t i o n were well established. I t also became evident that the nature of the reactive excited state (n.jr*^- or TT.TT*^) determines the course of a rea c t i o n when topochemical r e s t r i c t i o n s permit two or three possible reactions. Some examples of unimolecular reactions i n organic s o l i d state photochemistry are given i n Scheme 2 . -7-Scheme 2 -8-Reaction C a v i t y and S t e r i c Compression The o r i g i n a l topochemical p r i n c i p l e implies that a c e r t a i n degree of motion required f o r the rea c t i o n to occur i s to l e r a b l e i n the parent c r y s t a l l a t t i c e , but does not consider the constraining fac-tors due to the presence of neighboring molecules surrounding the rea c t i o n s i t e . Cohen modified the topochemical postulate by i n t r o -ducing the concept of the "reaction c a v i t y " . The reactant molecules occupy some volume i n the c r y s t a l l a t t i c e and are bounded by neighboring molecules. The size and shape of t h i s c a v i t y depend on the packing arrangement of the l a t t i c e . According to Cohen, the rea c t i o n pathway invo l v i n g a minimal d i s r u p t i o n of the shape of the rea c t i o n c a v i t y (due to motions during the reaction) would be pre-f e r r e d to those which disrupt the rea c t i o n c a v i t y to a greater extent. In t h i s context, another term introduced i s the " s t e r i c c ompression".^ a The s t e r i c compression concept i s more s p e c i f i c and well defined than the rea c t i o n c a v i t y concept, and implies that i f the reactant molecules during the course of the rea c t i o n come into a c l o s e r contact with neighboring molecules, the s t e r i c repul-s i o n caused would impede the reaction. Thus, the rea c t i o n pathway going v i a a minimal increase i n l a t t i c e energy would be preferred. To summarize, i t i s now well established that besides the topo-chemical (geometric) requirements f o r a reaction to take place i n the c r y s t a l l i n e medium, the a v a i l a b i l i t y of free space around the re a c t i o n s i t e i s equally important.^ - 9 -Apparent V i o l a t i o n s of the Topochemical P r i n c i p l e While the topochemical principle was being established, the strange solid state photobehavior of anthracene and some substituted anthra-cenes attracted the attention of solid-state photochemists. Based on their X-ray crystal structures, anthracene and 1 , 8 - d i c h l o r o - 9 -methylanthracene are not expected to dimerize in the solid state, as the topochemical requirements were not met. However, UV irradiation of these crystals results in appreciable yields of d i m e r s . 2 0 ' 2 1 j n case of 9-cyanoanthracene, the crystal structure predicts the formation of a mirror symmetric head-to-head dimer, whereas centrosymmetric head-t o - t a i l dimer i s formed in reality (Scheme 3 ) . ^ 2 CM CN mirror symmetric dimer expected centrosymmetric dimer formed Scheme 3 -10-I t i s b e l i e v e d t h a t i n these cases, the s t r u c t u r a l i mperfections of the c r y s t a l , which are not detectable by usual X-ray d i f f r a c t i o n methods, p l a y an important r o l e i n t h e i r photobehavior. As the symmetry at d e f e c t s i t e s i s d i s t u r b e d , the o r i e n t a t i o n of the molecules at such l o c a t i o n s might be q u i t e d i f f e r e n t from that which would be expected from the s p a t i a l l y averaged c r y s t a l s t r u c t u r e . I f the photochemical r e a c t i o n occurs mainly at defect s i t e s , that would e x p l a i n the anomalous behavior. This i s s t i l l open f o r debate, as i t has not been c o n c l u s i v e l y proved i n a l l cases (mainly because there i s no d i r e c t experimental method y e t a v a i l a b l e to o b t a i n exact s t r u c t u r a l i n f o r m a t i o n on molecules at d e f e c t s i t e s ) t h a t s t r u c t u r a l imperfections are completely r e s p o n s i b l e f o r unexpected photobehavior. Ample evidence i n support of the r o l e played by defects comes from o p t i c a l , e l e c t r o n microscopy and luminescence s t u d i e s . 2 2 - 2 6 Dynamic Preformation Another concept which i s found to be u s e f u l i n understanding photo-chemical r e a c t i o n s i n the s o l i d s t a t e i s "dynamic preformation" suggested by C r a i g and co-workers.27-30 According to C r a i g et a l . , e x c i t a t i o n of a molecule i n the c r y s t a l l a t t i c e may r e s u l t i n moving the e x c i t e d molecule from i t s e q u i l i b r i u m ground s t a t e p o s i t i o n c l o s e r to one of the nearest neighbors, and i f a chemical r e a c t i o n occurs under such c o n d i t i o n s , the r e a c t i o n may be thought of as being dynamically preformed f o l l o w i n g the e x c i t a t i o n . C r a i g et a l . , have a l s o shown through c a l c u l a --11-tions that such a l o c a l i n s t a b i l i t y of the l a t t i c e caused by e x c i t a t i o n may be relaxed by greater displacements of the molecules from t h e i r e q u i l i b r i u m ground state p o s i t i o n s . I t i s also b e l i e v e d that the at t r a c -t i v e forces between the molecules would be enhanced upon e x c i t a t i o n . The Di-II-Methane Rearrangement Like the Norrish type II reaction, the di-7r-methane rearrangement i s a general photochemical reaction which has been extensively studied i n s o l u t i o n . Since the recognition of i t s generality, many aspects of the di-7r-methane reaction, namely, m u l t i p l i c i t y , r e g i o s e l e c t i v i t y , stereochemistry and substituent e f f e c t s have been thoroughly i n v e s t i -gated. This reaction, also termed the Zimmerman rearrangement a f t e r the name of the researcher who contributed most to our understanding of i t , i s now providing i n t e r e s t i n g r e s u l t s i n the s o l i d s t a t e . ^ The di-7r-methane rearrangement involves the photochemical forma-t i o n of a vinylcyclopropane from a 1,4-diene. A simple representation of the mechanism i s shown i n Scheme 4. The mechanism consists of i n i t i a l 2-4 bonding to give a c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l which opens to give a 1, 3 - b i r a d i c a l . Vinylcyclopropane i s formed as a consequence of the collapse of t h i s 1,3-biradical.^2 - 1 2 -// <v ° Scheme 4 Evidence f or t h i s mechanism came from the photochemical conversion of hexadeuterobarrelene to semibullvalene, i n which the hydrogen l a b e l s end up i n the posit i o n s predicted by the mechanism (Scheme 5 ) . ^ a (• represents H label, deuterium elsewhere) Scheme 5 M u l t i p l i c i t y and Regie-selectivity of Di-II-Methane Rearrangement I t became evident through various examples that, i n general, a c y c l i c di-jr-methane systems rearrange v i a t h e i r s i n g l e t excited.states, whereas the corresponding b i c y c l i c systems rearrange v i a t h e i r t r i p l e t excited states (Scheme 6 ) . ^ This has been a t t r i b u t e d , i n the case of a c y c l i c systems, to a " f r e e - r o t o r " e f f e c t which causes the decay of t r i p l e t s f a s t e r than the rearrangement, but apparently cannot compete with the rates of rearrangement of t h e i r s i n g l e t s . Singlets of b i c y c l i c systems usually have other reaction pathways ( e l e c t r o c y c l i c rear-rangements) open to them, the rates of which dominate that of di-?r-methane rearrangement. As a consequence, the b i c y c l i c di-w-methane Scheme 6 -14-systems rearrange only v i a t h e i r t r i p l e t s . In these cases, free-rotor decay through bond r o t a t i o n i s not as e f f e c t i v e because of the r i g i d r i n g systems. The most i n t e r e s t i n g aspect of the di-jr-methane rearrangement i s the r e g i o s e l e c t i v i t y which arises i n cases where the two ir systems are d i f f e r e n t l y substituted. This p o s s i b i l i t y a r i s e s due to the f a c t ( i l l u s -t r a t e d i n Scheme 7) that the c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l has two d i f f e r e n t ways of opening to a 1,3-biradical, each of which i n turn leads to a d i f f e r e n t regioisoraer. Study of various di-jr-methane systems with unequal s u b s t i t u t i o n l e d to an understanding that, i n the opening of the c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l , the most s t a b i l i z e d r a d i c a l i s retained. In cases where one of the two n bonds i s part of a phenyl r i n g , the c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l i s opened i n such a way as to regenerate the aromaticity (Scheme 8 ) . I t has also been noted that electron-donating groups present on the c a r b i n y l carbon of the cyclop r o p y l d i -prpferred mechanism A Ph Ph Ph Ph Scheme 7 - 1 5 -Scheme 8 c a r b i n y l d i r a d i c a l help i n r i n g opening and become part of the ir-bond i n the f i n a l product, whereas electron-withdrawing groups s t a b i l i z e the ca r b i n y l carbon r e t a i n i n g the r a d i c a l and become part of the cyclopropane - 1 6 -r i n g o f t he f i n a l p r o d u c t (Scheme 8 ) . T h i s has b e e n a t t r i b u t e d t o the e l e c t r o n - r i c h n a t u r e o f t he c a r b i n y l c a r b o n s o f t he c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l . D i - I I - M e t h a n e R e a r r a n g e m e n t o f D i b e n z o b a r r e l e n e s D i - j r - m e t h a n e r e a r r a n g e m e n t o f d i b e n z o b a r r e l e n e and i t s d e r i v a t i v e s i n s o l u t i o n was f i r s t r e p o r t e d i n 1966 b y C i g a n e k , ^ a n & n e n o t e d t h e i n t e r e s t i n g r e g i o s e l e c t i v i t y o b s e r v e d i n c a s e s where t he d i b e n z o -b a r r e l e n e was d i f f e r e n t l y s u b s t i t u t e d (Scheme 9) . F o l l o w i n g t h i s C0 2 Me 67:33 Scheme 9 i n t e r e s t i n g o b s e r v a t i o n , t h e p h o t o i s o m e r i s a t i o n o f a s e r i e s o f d i b e n z o -b a r r e l e n e d i e s t e r s h a v i n g a b r i d g e h e a d s u b s t i t u e n t o f g e n e r a l s t r u c t u r e 1 (Scheme 10) were s t u d i e d i n s o l u t i o n . 3 4 - 3 6 j^e p r i m e i n t e r e s t o f t h e s e s t u d i e s was c e n t e r e d on d e r i v i n g a r e l a t i o n s h i p b e t w e e n t h e n a t u r e o f the bridgehead substituent and the observed r e g i o s e l e c t i v i t y of the di-n-methane rearrangement. The presence of a bridgehead substituent on an otherwise symmetric dibenzobarrelene d i e s t e r introduces the p o s s i b i l -i t y of having two d i f f e r e n t pathways f or di-7r-methane rearrangement. These two pathways (paths a and b, Scheme 10) d i f f e r i n the s i t e of i n i t i a l vinyl-benzo bridging, and consequently lead to d i f f e r e n t regie-s' B Scheme 10 isomers. The r e s u l t s obtained by Iwamura et a l . , ^ are given i n Table 1. The observed r e g i o s e l e c t i v i t y was explained i n terms of the r e l a -t i v e s t a b i l i t y of the cy c l o p r o p y l d i c a r b i n y l d i r a d i c a l s formed v i a paths a -18-and b. The e f f e c t of a s u b s t i t u e n t X on the st r e n g t h of the new v i n y l -behzo bond formed to give c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l , B', was r a t i o n -X Path a Path b OCH3 100 % 0 % OAc 100 0 OCOPh 100 0 CH 3 71 29 (CH 3) 2CH 77 23 (CH 3) 3C 100 0 Br 100 0 Ph 0 100 Ac 71 29 CHO 88 12 N0 2 100 0 Table 1 : R e g i o s e l e c t i v i t i e s of di-7r-methane rearrangement of 1 observed by Iwamura et a l . a l i z e d by Iwamura et a l . , i n the same way as the e f f e c t of a corner s u b s t i t u e n t R, on the stre n g t h of the opposite bond of the cyclopropane r i n g i n the e q u i l i b r i u m between norcaradiene and c y c l o h e p t a t r i e n e (Scheme 11).-^ I t was shown^^ that the Walsh o r b i t a l s of the cyclopropane i n t e r a c t i n a 7r-manner w i t h 7 r-acceptors so as to strengthen the -19-opposite C-C bond i n the cyclopropane r i n g , and w i t h 7r-donors so as to weaken the same bond. Thus, i f X i s an e l e c t r o n donating or e l e c t r o -negative group (such as OCH3 or Br i n Table 1), i t would d e s t a b i l i z e the cyclopropane r i n g i n d i r a d i c a l B' by weakening the new vinyl-benzo bond formed, and d i r a d i c a l A' i s p r e f e r e n t i a l l y formed e x p l a i n i n g the r e g i o i s -omer obtained. S i m i l a r l y , i f X i s an e l e c t r o n withdrawing group, i t should i n p r i n c i p l e s t a b i l i z e the cyclopropane r i n g i n d i r a d i c a l B' l e a d i n g to the regioisomer B. To e x p l a i n the observed r e g i o s e l e c t i v i t y when X i s an e l e c t r o n withdrawing group (Ph, Ac, CHO, NO2 i n Table 1), i t was argued t h a t the e l e c t r o n e g a t i v i t y of X i s a c t i n g against the p r e f e r e n t i a l b-b r i d g i n g . Thus the phenyl group, being l e a s t e l e c t r o n e g a t i v e , leads e x c l u s i v e l y to regioisomer B, whereas the most e l e c t r o n e g a t i v e n i t r o group leads e x c l u s i v e l y to regioisomer A. When X i s an a l k y l group, the b - b r i d g i n g i s i n h i b i t e d due to s t e r i c hindrance. Another c l a s s of dibenzobarrelene d i e s t e r s , c u r r e n t l y being i n v e s t i -gated i n our l a b o r a t o r y , f o r di-'w-methane rearrangement both i n s o l u t i o n Scheme 11 -20-and the s o l i d state, i s of general structure 2 (Scheme 12). lb In these C 0 2 R ' •ol id s la te of solution C 0 2 R [ C 0 2 R C 0 2 R ' | C 0 2 R a) R=R'=CHMe J b) R=Me, R'=CHM 3 4 Scheme 12 compounds, the difference i n photorearrangement products i s caused by having two d i f f e r e n t ester groups instead of a bridgehead substituent (Scheme 12), which can be understood i n the same way as described e a r l i e r (see Scheme 10). I n t e r e s t i n g l y , i t was found that, i n the s o l i d state, the r e g i o s e l e c t i v i t y observed i s higher than i n s o l u t i o n . For example, i n the case of 2b, the r a t i o of 3 to 4 i n s o l u t i o n i s 45:55 and i n the s o l i d state i t i s 3:97.^ The X-ray c r y s t a l structure of the mixed d i e s t e r 2b revealed that one of the ester functions i s more conjugated with the c e n t r a l double bond than the other. This means that only one of the two possible c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l s w i l l be s t a b i l i z e d through conjugation with the ester carbonyl group. Thus, i t was i n i t i a l l y thought that the regioisomer produced as a major product i n the s o l i d state would be the one forming v i a the d i r a d i c a l s t a b i -- 2 1 -l i z e d by conjugation with the ester group. But t h i s i s not what was observed. The regioisomer expected to be minor based on the r a d i c a l s t a b i l i z a t i o n i s a c t u a l l y found to be the major product. This was r a t i o n a l i z e d on the basis of the intermolecular packing i n the crys-t a l l a t t i c e . I t was observed that there i s not enough free space around the methyl ester which i s necessary f o r the movement occur-r i n g during the vinyl-benzo b r i d g i n g to give the d i r a d i c a l . This i s supported by " l o c a l packing density" c a l c u l a t i o n s , i n which i t was observed that movement of the methyl ester to a c e r t a i n extent would increase the l a t t i c e energy enormously compared to that of the iso-propyl e s t e r . - " This i s c l e a r l y an example, where the topochemical factors of the s o l i d state completely dominate the st e r e o e l e c t r o n i c factors which guide the course of a rea c t i o n i n so l u t i o n . In t h i s context, i t i s worth mentioning that the d i e s t e r 2 a i s found to be dimorphic, and one of the forms i s c h i r a l (space group P 2 ^ 2 ^ 2 ^ ) . I r r a d i a t i o n of large single c h i r a l c r y s t a l s of 2 a y i e l d e d the photoproduct i n 1 0 0 % enantiomeric excess.^ 0 This provides the f i r s t example of an absolute asymmetric synthesis i n a s o l i d state unimolecular reaction. Another i n t e r e s t i n g r e s u l t obtained was the s o l i d state t r i p l e t s e n s i t i z a t i o n of the photorearrangement of dibenzobarrelene i t s e l f . ^ In s o l u t i o n , the s i n g l e t excited state of dibenzobarrelene i s known to give dibenzocyclooctatetraene, whereas the t r i p l e t gives dibenzosemibull-vallene, the di -7r-methane reaction p r o d u c t . ^ • ^ i n the s o l i d state, photolysis of dibenzobarrelene leads to both s i n g l e t and t r i p l e t -22-products i n a r a t i o of 80:20.^ Upon s e n s i t i z e d photolysis i n the s o l i d state using xanthone, benzophenone or 7-phenylbutyrophenone i n the form of a s o l i d s o l u t i o n obtained by c o - c r y s t a l l i z a t i o n from the melt, only the t r i p l e t product was obtained, demonstrating the pos-s i b i l i t y of s o l i d state s e n s i t i z a t i o n . Thus, s o l i d state photorearrangements of dibenzobarrelenes are pro-v i d i n g some i n t e r e s t i n g new phenomena, and paving the way for a bett e r understanding of s t r u c t u r e - r e a c t i v i t y r e l a t i o n s h i p s at the molecular l e v e l . Objectives of the Present Work The main objective of the present research i s to study the photo-chemistry of compound 5 (Dimethyl 9,10-dihydro-9-methyl-9,10-etheno-anthracene-11,12-dicarboxylate) both i n s o l u t i o n and i n the s o l i d state, and to determine i t s c r y s t a l structure i n order to obtain s t r u c t u r e - r e a c t i v i t y r e l a t i o n s h i p s . 14 15 Compound 5 Some important questions (given below) concerning the photochemis t r y of compound 5 w i l l be investigated i n the present research. 1. What i s the e f f e c t of the c r y s t a l l i n e medium on the r e g i o s e l e c t i v i t of the photorearrangement? *: C r y s t a l l o g r a p h i c numbering of the carbon atoms i s indicated and i s followed i n assigning NMR spectra of a l l the compounds i n t h i s t h e s i s . -24-2. What i s the e f f e c t of the bridgehead methyl substituent on the molecular conformation and intermolecular packing arrangement adopted i n the c r y s t a l l a t t i c e , which i n turn c o n t r o l the s o l i d state photochemistry? 3. What i s the e f f e c t of grinding the c r y s t a l s on the r e g i o s e l e c t i -v i t y of the photorearrangement? 4. What i s the e f f e c t of pressure on the s o l i d state photochemical reaction? F i n a l l y , compound 5 w i l l be investigated f o r the p o s s i b i l i t y of s o l i d state t r i p l e t s e n s i t i z a t i o n . - 2 5 -RESULTS AND DISCUSSION -26-Synthesls of S t a r t i n g M a terial Preparation of dimethyl 9,10-dihydro-9-methyl-9,10-ethenoanthracene-11,12-dicarboxylate (compound 5) was accomplished by a Diels-Alder addition r e a c t i o n between 9-raethylanthracene and dimethyl acetylenedicarboxylate (Scheme 13) with a s l i g h t modification of the procedure of R. G. Paddick et al.^- * The compound was p u r i f i e d by several r e c r y s t a l l i z a t i o n s from ethanol and chloroform mixture . The structure of compound 5 was 5 Scheme 13 confirmed by various spectroscopic and a n a l y t i c a l data (given i n the experimental section), which very well match with those reported i n the l i t e r a t u r e , ^  and also by the X-ray c r y s t a l structure (discussed l a t e r ) . -27-Solution Phase Photochemistry of Compound 5 Acetone-sensitized photisomerization of compound 5 was f i r s t reported i n 1976 by R. G. Paddick et al.^5 This paper also reported the di-w-methane rearrangement of a number of dibenzobarrelene d i e s t e r s having d i f f e r e n t bridgehead substituents. In the case of compound 5, the authors observed a 65:35 r a t i o of the di-7r-methane rearrangement products 7 and 8 (Scheme 14). In 1980, i n a s i m i l a r study, H. Iwamura 8 Scheme 14 et a l . - ^ reported a 71:29 r a t i o of compounds 7 and 8 f o r di - 7 r -methane rearrangement of compound 5 i n acetone; there are no reports i n the l i t e r a t u r e of d i r e c t i r r a d i a t i o n of t h i s compound. In the present study, compound 5 was photolysed i n acetone as well as i n no n - s e n s i t i z i n g solvents l i k e benzene (benzene can be a s e n s i t i z i n g -28-solvent at A < 290 nm) and a c e t o n i t r i l e . I n t e r e s t i n g l y , upon d i r e c t i r r a d i a t i o n , a new product (compound 6) was obtained along with the di -5r-methane rearranged products (Scheme 1 5 ) . In acetone-sensitized photol y s i s also a trace amount of 6 was detected by GC. When s e n s i t i z e d Scheme 15 by xanthone (1%) or benzophenone (4%) i n a c e t o n i t r i l e , only trace amounts of 6 were detected. This suggests that the new product (6 ) i s formed v i a the s i n g l e t excited state. The product r a t i o s observed i n a l l the three solvents studied are summarized i n Table 3 , p 36. -29-C h a r a c t e r i s a t i o n of the Photoproducts Photoproducts 7 and 8 were distinguished based on the chemical s h i f t s of NMR s i g n a l s . The methine protons of 7 and 8 are expected to resonate i n the range of S 4.2-4.5 and 5.0-5.1 ppm r e s p e c t i v e l y . - ^ The observed values of S f o r the methine protons of 7 and 8 are 4.34 and 5.06 ppm re s p e c t i v e l y , which very well match those reported (4.38 for 7 and 5.06 f o r 8) by Paddick et a l . ^ Other spectroscopic data also support the structures assigned for compounds 7 and 8. The structure of the s i n g l e t product, 6, i s also assigned mainly based on the and 13 1 i J C NMR spectra. The •LH NMR signal of the v i n y l proton of 6 i s expected to appear i n the aromatic proton r e g i o n . ^ • ^ T h e value of 5 reported for the o l e f i n i c protons of unsubstituted dibenzocyclooctate-traene i s 6.71 ppm,^ and the v i n y l proton of compound 9 was found to resonate i n the range 7.05-7.60 ppm along with eight aromatic protons. AcHN C0 2M« Compound 9 In the present study, the s i n g l e t at 8.07 ppm i n the NMR spectrum of 6 i s interpreted as being due to the v i n y l proton of the cyclooctate--30-traene, and the m u l t i p l e t at 7.03-7.22 ppm as being due to the aromatic protons. A NMR N.O.E. difference experiment was performed on 6 i n order to see whether the v i n y l hydrogen and the v i n y l methyl are present on the same C=C double bond of the eight membered r i n g . I r r a d i a t i o n of v i n y l methyl hydrogens ( s i n g l e t at 5 2.35 ppm) re s u l t e d i n the enhancement of a s i n g l e t at 3.68 ppm (due to the methyl hydrogens of one of the two ester groups) and a doublet at 7.08 (aromatic hydrogen). This c l e a r l y i n d i c a t e s that the v i n y l hydrogen and the v i n y l methyl group are on d i f f e r e n t double bonds, but does not d i s t i n g u i s h the following two structures possible f o r 6 (Figure 1). I t was assumed, based on the Figure 1 : Two structures possible for compound 6. mechanism of i t s formation (given i n Scheme 17), that the actual structure of 6 i s the l e f t structure shown i n Figure 1, which i s also s i m i l a r to the stru c t u r e assigned to 9 formed by the same mechanism. ^ 5 This structure was also supported by the other spectroscopic data (IR, MS), and no fu r t h e r attempt was made to confirm the structure assigned. -31-I d e n t i f i c a t i o n of S t a r t i n g M a t e r i a l and Photoproducts by Gas Chromatography A l l analyses (percentage product r a t i o determination, etc.) were c a r r i e d out by gas chromatography. A t y p i c a l gas chromatogram of the p h o t o l y s i s mixture contains peaks at r e t e n t i o n times (RT) 5.9, 7.6, 8.3, 8.6, and 9.3 min. The l a s t peak i s due to the s t a r t i n g mate-r i a l , 5. A l l other peaks were i d e n t i f i e d by s e p a r a t i n g and a n a l y s i n g the separate components of the p h o t o l y s i s mixture ( d e t a i l s are given i n the Experimental s e c t i o n ) . The f i r s t two peaks were i d e n t i f i e d as compounds 6 and 7 r e s p e c t i v e l y , whereas peaks w i t h RT's 8.3 and 8.6 min were assumed to be due to compound 8 , which i s probably decomposing on the GC column to show two peaks. This i s not unreason-able c o n s i d e r i n g the GC c o n d i t i o n s (270 °C, i n j e c t o r temperature; 200 °C, oven temperature) and the s t e r i c s t r a i n caused by the pres-ence of three bulky groups (a methyl and two carbomethoxy groups) on the cyclopropane r i n g of 8 . The o i l showing two peaks on GC was chromatographed on a s i l i c a g e l column, but n e i t h e r of the two separated components (with RT's 8.3 and 8.6) showed the same NMR spectrum as the s t a r t i n g o i l on which the s i l i c a g e l column chromato-graphy was performed. Based on the sp e c t r o s c o p i c data of the o i l showing two peaks on GC, i t was concluded that t h i s o i l i s a c t u a l l y compound 8 and i s decomposing on the GC column as w e l l as on a s i l i c a g e l column, but no attempt was made to determine the decomposition products. Th e r e a f t e r , the sum of the i n t e g r a t e d areas of the peaks -32-with RT's 8.3 and 8.6 were added to ca l c u l a t e the percentage of 8. The f a c t that the s t a r t i n g material and the photoproducts have d i s t i n c t methyl resonance signals i n •'•H NMR spectrum (5, 1.92 f o r 7, 2.01 for 8, 2.18 f o r s t a r t i n g material, and 2.35 for 6) was used to obtain the photoproduct r a t i o s from the i n t e g r a t i o n of the methyl sig n a l s ; these r e s u l t s were compared with those obtained from the GC i n t e g r a t i o n and are given i n Table 2. Solvent Compound Percentage NMR GC Acetone 54.6 5.1 33.2 7.1 59.5 4,7 28.7 4.0 A c e t o n i t r i l e 50.6 11.4 31.6 6.3 53.6 8.9 29.0 4.3 Benzene 5 6 7 8 71.0 3.8 22.0 3.2 69.9 4.0 19.3 1.5 Table 2 : Comparison of photoproduct r a t i o s obtained from the NMR i n t e g r a t i o n and the GC integration. -33-Discussion of the Solution Photochemical Results Possible r e a c t i o n mechanisms for the di-n-methane rearrangement of 535,36 a n ( j £ o r t n e f o r m a t i o n of dibenzocyclooctatetraene 6 ^ are given i n Schemes 16 and 17 res p e c t i v e l y . Scheme 16 -35 -six •electron fragmentation 6 Scheme 17 The e f f e c t of bridgehead substituents on the r e g i o s e l e c t i v i t y of the di-»r-methane rearrangement of dibenzobarrelene die s t e r s was explained by Paddick et a l . , ^ 5 based on the e l e c t r o n e g a t i v i t y or the hydrogen bonding a b i l i t y (with the neighboring carbonyl of the ester group) of the substi-tuent present on the bridgehead carbon, which favors or disfavors one of the two c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l s involved i n the photorearrange-ment. According to these authors, the more electronegative the s u b s t i -tuent, the more the vinyl-benzo bond formation at the near end of the substituent i s disfavored; t h i s was a t t r i b u t e d to the reluctance of -36-cyclopropane r i n g i n the c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l to have the e l e c t r o n e g a t i v e group attached by a bond hig h i n s c h a r a c t e r . ^ Thus, when Br i s the bridgehead s u b s t i t u e n t , no product formed v i a path b i s observed, whereas i n the cases of bridgehead methoxy or ethoxy groups 15% of the product i s formed v i a path b, and 35% of the corresponding product i n the case of bridgehead methyl group. This has been a t t r i b -uted to the decreasing e l e c t r o n e g a t i v i t y of the s u b s t i t u e n t s (CTT_-Br +0.44, ^i_0Me -OEt +0-29, ffj_Me -0.08). Iwamura et a l . , ^ e x p l a i n e d the p r e f e r e n t i a l rearrangement of 5 v i a path a to be due to the s t e r i c i n h i b i t i o n t hat may be i n v o l v e d i n the formation of BR-8 v i a path b. The product r a t i o s observed i n the present study are s i m i l a r to those reported-^ and are given i n Table 3. Solvent Phot 6 oproducts 7 (%) 8 7/8 Acetone 2 76 22 ±1 3.5 A c e t o n i t r i l e 36 52 12 ±3 4.3 Benzene 30 55 15 ±2 3.7 Table 3 : The photoproduct r a t i o s obtained i n three solvent media. Upon d i r e c t i r r a d i a t i o n , monobenzo-, dibenzobarrelene and some of t h e i r d e r i v a t i v e s were reported to give good y i e l d s of the corresponding -37-c y c l o o c t a t e t r a e n e s , and i t was n o t e d t h a t d i r e c t i r r a d i a t i o n and t h e a b s e n c e o f a g roup w h i c h c a n s t a b i l i z e a r a d i c a l by d e l o c a l i z a t i o n i s r e q u i r e d f o r t h e f o r m a t i o n o f c y c l o o c t a t e t r a e n e s . ^ T h i s i s i l l u s t r a t e d i n Scheme 1 8 , where d i r e c t i r r a d i a t i o n o f 10 l e a d s e x c l u s i v e l y t o d i - ? r -methane r e a r r a n g e d p r o d u c t , and p h o t o l y s i s o f 11 g i v e s o n l y t h e c o r r e -s p o n d i n g c y c l o o c t a t e t r a e n e d e r i v a t i v e , 42a T h i s h a s b e e n a t t r i b u t e d t o t he c o n j u g a t e d d o u b l e bond i n t h e c a s e o f 10 w h i c h c a n s t a b i l i z e t h e Scheme 18 r a d i c a l c e n t e r i n v o l v e d i n t h e d i -» r -me thane r e a r r a n g e m e n t , b u t i s l a c k i n g i n 11 f a v o r i n g t h e s i n g l e t r e a c t i o n t o g i v e c y c l o o c t a t e t r a e n e . F o r m a t i o n o f a c y c l o o c t a t e t r a e n e d e r i v a t i v e ( 9 , p 29) was o b s e r v e d i n a c e t o n e --38-s e n s i t i z e d p h o t o l y s i s of a dibenzobarrelene d i e s t e r having an acetamido o c group at the bridgehead p o s i t i o n . In the present study, c y c l o o c t a t e -traene d e r i v a t i v e 6 i s obtained upon d i r e c t i r r a d i a t i o n , but as can be seen i n Table 3, the t r i p l e t r e a c t i o n l e a d i n g to semibullvalenes 7 and 8 accounts f o r a major p a r t of the r e a c t i o n . This may be due to a r a p i d i n t e r s y s t e m c r o s s i n g dominating the r a t e of s i n g l e t r e a c t i o n . I t can a l s o be seen w i t h the help of the data given i n Table 3, that the t r i p l e t product r e g i o s e l e c t i v i t y ( i e 7 vs 8) i s roughly constant i n a l l the three s o l v e n t s s t u d i e d . S o l i d State Photochemistry of Compound 5 C r y s t a l s of 5 were i r r a d i a t e d u s i n g a N 2 l a s e r (A=337 nm) f o r consi d e r a b l e periods of time, but no conversion to products was detected by GC. This was found (as w i l l be discussed l a t e r ) to be due to the f a c t that t h i s compound does not absorb l i g h t (both i n s o l u t i o n as w e l l as i n the s o l i d s t a t e ) at the wavelength of operation of the l a s e r used. I r r a d i a t i o n of the c r y s t a l s u s i n g a Hanovia lamp w i t h a Pyrex' f i l t e r (A>290 nm) r e s u l t e d i n photochemical r e a c t i o n , but the percent conversion w i t h time of i r r a d i a t i o n was found to be very low. I t was a l s o observed that the product r a t i o s obtained when the c r y s t a l s were photolysed are d i f f e r e n t from those obtained upon p h o t o l y s i n g a powdered sample. The r e s u l t s are given i n Table 4. -39-State Photoproducts (%) 7 / 8 6 7 8 C r y s t a l s 6 12 82 ±2 0.15 Powder 3 35 62 ±1 0.56 Table 4 : The photoproduct r a t i o s obtained i n the s o l i d s t a t e . The f o l l o w i n g observations can be made by examining the r e s u l t s shown i n Table 4: (1) The product r a t i o s are d i f f e r e n t from those observed i n s o l u t i o n (Table 3, p 36). (2) The r e g i o s e l e c t i v i t y of the t r i p l e t photorearrangement (7 vs 8) i n c r y s t a l s i s higher and i s reverse of the s e l e c t i v i t y observed i n s o l u t i o n ; and the r a t i o of 7 to 8 i s co n s i d e r a b l y a f f e c t e d upon powdering the c r y s t a l s . (3) I r r a d i a t i o n of both c r y s t a l s and powdered samples gives only a small amount of the s i n g l e t product, 6 . D i s c u s s i o n of the S o l i d State Photochemical Results Formation of l e s s e r amounts of 6 i n the s o l i d s t a t e may be under-stood by c o n s i d e r i n g the d i f f i c u l t y of the formation of the [2+2] adduct ( f i r s t step of the s i n g l e t r e a c t i o n l e a d i n g to the c y c l o o c t a t e t r a e n e ) as opposed to the formation of a vinyl-benzo bridge ( f i r s t step of the -40-t r i p l e t r e a c t i o n leading to semibullvalene) due to the intermolecular packing e f f e c t s present i n the c r y s t a l l a t t i c e . To give the [2+2] adduct, both the c e n t r a l ethylenic carbons should move to a bonding distance from the benzo carbons involved i n the addition, whereas f o r the forma-t i o n of a c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l , only one of the two ethylenic carbons needs to move to a bonding distance from the benzo carbon involved i n the bridge formation (see Schemes 16 and 17). Thus, i n the s o l i d state the s i n g l e t r e a c t i o n may have been i n h i b i t e d due to the s t e r i c factors opposing the i n i t i a l [2+2] adduct formation. R e g i o s e l e c t i v i t y of the Di-7r-Methane Rearrangement i n the S o l i d State In l i g h t of the mechanism proposed (Scheme 16), the r e g i o s e l e c t i v i t y of the t r i p l e t di-7r-methane rearrangement i n the s o l i d state may be explained with the help of e l e c t r o n i c and s t e r i c factors (discussed below), which are expected to control the reaction. Influence of E l e c t r o n i c Factors In the S o l i d State In s o l u t i o n , both the ester groups are equally conjugated (as evidenced by the presence of an average mirror plane of symmetry indic a t e d by NMR spectrum i n solution) with the c e n t r a l double bond, whereas i n the s o l i d state, as shown by the X-ray c r y s t a l structure, only one of the two carbomethoxy groups i s conjugated to -41-the c e n t r a l double bond, while the other i s non-conjugated. I n f a c t , examination of the c r y s t a l s t r u c t u r e data (discussed on p 66) i n d i c a t e s t h a t the carbonyl group of the e s t e r f u r t h e s t away from the bridgehead methyl s u b s t i t u e n t i s conjugated, and hence the c y c l o p r o p y l d i c a r b i n y l d i r a d i c a l (BR-8, Scheme 16) i n which a r a d i c a l i s p l a c e d on the carbon b e a r i n g t h i s e s t e r group should be s t a b i -l i z e d through conjugation and l e a d to the major product i n the s o l i d s t a t e . This i s a c t u a l l y found to be the case i n the s o l i d s t a t e photo-l y s i s of 5 (Table 4). Role of Packing E f f e c t s i n the C r y s t a l L a t t i c e As e x p l a i n e d e a r l i e r i n the I n t r o d u c t i o n (see p 3, 21), the i n t e r -molecular packing e f f e c t s i n the c r y s t a l l a t t i c e may p l a y a dominant r o l e i n d e c i d i n g the course of a photochemical r e a c t i o n . E l e c t r o n i c f a c t o r s , as i n t h i s case, favor one of the two p o s s i b l e vinyl-benzo b r i d g i n g s i t e s through conjugation, the s t e r i c f a c t o r s imposed by the l a t t i c e may favor one pathway over the other. In other words, the a v a i l a b i l i t y of f r e e space around the e s t e r groups decides the major b r i d g i n g s i t e and hence the major product i n the s o l i d s t a t e . In the present study, no c a l c u l a t i o n s (such as l o c a l packing d e n s i t y c a l c u l a t i o n s ) were performed to determine the e f f e c t of the l a t t i c e i n d e c i d i n g which one of the two e t h y l e n i c carbons forms a bridge i n v o l v i n g the l e a s t increase i n the l a t t i c e energy. As observed i n our l a b o r a t o r y , ^ • ^ whenever the e l e c t r o n i c f a c t o r s and s t e r i c f a c t o r s oppose each other i n -42-d e c i d i n g the major s o l i d s t a t e photochemical r e a c t i o n pathway, the s t e r i c f a c t o r s were found to dominate. In such cases, the major product i n the s o l i d s t a t e was the one favored by the i n t e r m o l e c u l a r packing e f f e c t s . I n the case of 5 , the major product formed (8 ) i n the s o l i d s t a t e p h o t o l y s i s i s the one favored by the e l e c t r o n i c f a c t o r s , and so i t i s not unreasonable, based on our experience w i t h s i m i l a r systems, to assume t h i s to be the product favored by the s t e r i c f a c t o r s present i n the l a t t i c e . E f f e c t of Powdering the C r y s t a l s on the R e g i o s e l e c t i v i t y of the Di-II-Methane Rearrangement of 5 An e m p i r i c a l o b servation on the e f f e c t of g r i n d i n g the c r y s t a l s on the r e g i o s e l e c t i v i t y of the di-7r-methane rearrangement of 5 (Table 4) l e d to a more systematic i n v e s t i g a t i o n , i n which c r y s t a l s of 5 were ground usi n g a mechanical g r i n d e r , and samples c o l l e c t e d a f t e r d i f f e r e n t periods of g r i n d i n g were photolysed. I n t e r e s t i n g l y , a r e g u l a r change i n the t r i p l e t product r a t i o s was observed w i t h the time of g r i n d i n g . The r e s u l t s are shown i n the form of a graph i n Figure 2 . - 4 3 -lOO-i Figure 2 : Graph showing the e f f e c t of grinding the c r y s t a l s on the photoproduct r a t i o s . -44-I t can be seen i n Figure 2, that g r i n d i n g of the c r y s t a l s r e s u l t s i n the l o s s of t r i p l e t product s e l e c t i v i t y (8 vs 7). The r a t i o 7/8 increases from 0.15 i n c r y s t a l s i r r a d i a t i o n to 0.56 i n the i r r a d i a t i o n of the powdered samples (Table 4), but i s s t i l l q u i t e low compared to the r a t i o observed i n s o l u t i o n (Table 3). The r e s u l t s obtained i n the g r i n d i n g s t u d i e s suggest e i t h e r one or both of the f o l l o w i n g c o n c l u s i o n s : (1) most of the r e a c t i o n i s occuring at the surface of the c r y s t a l , and the s e l e c t i v i t y at the surface i s d i f f e r e n t from that w i t h i n the b u l k of the c r y s t a l , or (2) there i s a phase t r a n s i t i o n i n the s o l i d s t a t e upon g r i n d i n g . With the help of X-ray powder d i f f r a c t i o n photographs of samples ground f o r d i f f e r e n t periods of time, i t should i n p r i n c i p l e be p o s s i b l e to determine i f there i s any phase t r a n s i t i o n i n the s o l i d s t a t e as a r e s u l t of g r i n d i n g . Since no such photographs were taken i n the present study, the p o s s i b i l i t y of a phase t r a n s i t i o n i n the s o l i d s t a t e which a l t e r s the photoproduct s e l e c t i v i t y upon g r i n d i n g cannot be r u l e d out. S i n g l e C r y s t a l P h o t o l y s i s In an attempt to see i f the r e a c t i o n i s o c c u r r i n g mainly at the s u r f a c e , a s i n g l e c r y s t a l of 5 (weighing 15 mg) was photolysed, a f t e r which the c r y s t a l was s t i l l transparent but had turned yellow. The uppermost l a y e r of the c r y s t a l was washed w i t h a few drops of d i e t h y l ether, i n which the s t a r t i n g m a t e r i a l i s s p a r i n g l y s o l u b l e , whereas the p h o t o l y s i s mixture i s f a i r l y s o l u b l e ( d e t a i l s are given i n the -45-Experimental s e c t i o n ) . The ether washing was analysed by GC. This procedure was repeated twice more and a l l the ether washings were analysed separately and also by mixing them together. The product r a t i o s observed were very i n t e r e s t i n g and are summarized i n Table 5. Ether Washing 6 (%) 7 8 % Conversion F i r s t 18 18 64 30 Second 11 10 79 7 T h i r d 6.5 6.5 87 3 Whole c r y s t a l d i s s o l v e d 11 11 78 1 Average of f i r s t three washings 12 11 77 Table 5 : Results of sin g l e c r y s t a l photolysis of 5. The r e s u l t s shown i n Table 5 suggest that most of the r e a c t i o n i s occurring at the surface, as the percent conversion i s higher i n the f i r s t washing than that observed for the l a t e r two washings. I t i s also i n t e r e s t i n g to note that the product r e g i o s e l e c t i v i t y i s higher i n the bulk compared to that at the surface, as can be seen by the increasing amounts of 8 observed i n the l a t e r two washings. By compar-ing the r a t i o s observed when the whole c r y s t a l was dissolved and analysed with the average of the f i r s t three washings, i t i s obvious -46-that the r e a c t i o n i s occurring only at or close to the surface. The fa c t that the r e g i o s e l e c t i v i t y at the surface i s low also explains the grinding r e s u l t s (Figure 2) where there i s a regular decrease observed i n the s e l e c t i v i t y with the time of grinding, as would be expected because the surface area increases with the extent of grinding. Photomicrographs of several single c r y s t a l s of 5 were taken before and a f t e r photolysis and are given i n Figures 3 and 4. At t h i s stage, i t can be pointed out that three d i f f e r e n t regioselec-t i v i t i e s of the t r i p l e t photorearrangement (7 vs 8) are observed, one i n s o l u t i o n and the other two at the surface and within the bulk of the c r y s t a l . Thus, the photochemical re a c t i o n of 5 i s found to be s e n s i t i v e to the environment i n which the reaction i s taking place. -47-Figure 3 Photograph of s e v e r a l s i n g l e c r y s t a l s of 5 before p h o t o l y s i s . - 4 8 -F i g u r e 4 : P h o t o g r a p h o f s e v e r a l s i n g l e c r y s t a l s o f 5 a f t e r p h o t o l y s i s . - 4 9 -UV-VIS Spectrum of 5 i n the S o l i d State I t was observed that the s o l i d s t a t e i r r a d i a t i o n of 5 (both c r y s t a l s and powder) r e s u l t s i n an intense y e l l o w c o l o u r , which does not fade away w i t h time (at l e a s t f o r a week) at ambient temperatures. I n the s i n g l e c r y s t a l p h o t o l y s i s i t was found that the ye l l o w c o l o u r was removed by d i e t h y l ether washing, implying that the coloured m a t e r i a l i s present i n the p h o t o l y s i s mixture. However, none of the photoproducts (6, 7 or 8) absorb l i g h t i n the v i s i b l e r e g i o n . In an attempt to get some i n f o r m a t i o n on the ye l l o w c o l o u r , a s o l i d s t a t e UV-VIS spectrum of 5 i n a KBr p e l l e t before and a f t e r the p h o t o l y s i s was obtained and i s shown i n Figure 5. I t can be seen i n Figure 5 that the absorption a f t e r p h o t o l y s i s i s broad and d i f f u s e and th e r e f o r e reveals no i n f o r m a t i o n on the m a t e r i a l respo-s i b l e f o r the co l o u r . So i t was assumed that some unknown m a t e r i a l formed upon p h o t o l y s i s may be r e s p o n s i b l e f o r the d i f f u s e absorp-t i o n . This assumption very w e l l e x p l a i n s the low r e a c t i v i t y of 5 ( i . e . s m a ll conversion to products w i t h time of i r r a d i a t i o n ) i n the s o l i d s t a t e because the yellow coloured m a t e r i a l formed over the surface absorbs most of the l i g h t t h e r e a f t e r and only a small i n t e n -s i t y of l i g h t i s passed through the c r y s t a l . Figure 5 a l s o shows th a t compound 5 does not absorb at 3 3 7 nm, e x p l a i n i n g the u n r e a c t i v i t y of 5 when i r r a d i a t e d u s i n g a N 2 l a s e r . -50-Figure 5 : UV-VIS spectrum of 5 i n KBr p e l l e t before and a f t e r p h o t o l y s i s . -51-S e n s i t i z e d Photolysis of 5 i n the S o l i d State Recently, s o l i d s t a t e t r i p l e t s e n s i t i z a t i o n of the di-7r-methane rearrangement of dibenzobarrelene was reported by Scheffer et al.^ Dibenzobarrelene undergoes m u l t i p l i c i t y - d e p e n d e n t photochemical r e a r -rangements, the s i n g l e t e x c i t e d s t a t e l e a d i n g to the formation of c y c l o o c t a t e t r a e n e ^ ^ a and the t r i p l e t under-going di-7r-methane r e a c t i o n to give dibenzosemibullvalene. D i r e c t i r r a d i a t i o n of dibenzobarrelene i n the s o l i d s t a t e was found to y i e l d mainly the s i n g l e t product, whereas s e n s i t i z e d i r r a d i a t i o n s gave e x c l u s i v e l y the t r i p l e t p r o d u c t . ^ In a c o n t i n u a t i o n of t h i s p i o n e e r i n g work, i n the present study, compound 5 was t e s t e d f o r the p o s s i b i l i t y of s o l i d s t a t e t r i p l e t s e n s i t i z a t i o n . The s e n s i t i z e r used was xanthone. A s o l i d s o l u t i o n (presumably) of (1% mol/mol) xanthone and 5 prepared by c o - c r y s t a l l i z i n g from the s e n s i t i z e r -r e a c t a n t melt was used f o r a l l s e n s i t i z e d p h o t o l y s i s experiments. S e n s i t i z e d i r r a d i a t i o n s were c a r r i e d out w i t h a n i t r o g e n l a s e r (A=337 nm) to a v o i d d i r e c t i r r a d i a t i o n (xanthone absorbs at t h i s w a v e l e n g t h ^ > but 5 does not, see UV spectrum of 5 i n the s o l i d s t a t e , p 50). The s e n s i t i z e d samples were i r r a d i a t e d i n two ways, one i n c r y s t a l l i n e form and another i n a KBr p e l l e t . Photochemical r e a c t i o n was found to occur, but the percent conversion to products w i t h time of i r r a d i a t i o n i n the case of c r y s t a l s was low. The r e s u l t s are summarized i n Table 6 . -52-Medium Pho toproducts (%) 6 7 8 A c e t o n i t r i l e 1 76 23 ±1 Crystals 33 17 50 ±3 KBr p e l l e t 45 29 26 ±3 Table 6 : Photoproduct r a t i o s obtained i n 1% (mol/mol) xanthone-s e n s i t i z e d i r r a d i a t i o n s . The f a c t that more of the presumed s i n g l e t product (6 ) i s obtained i n the t r i p l e t - s e n s i t i z e d photolysis i n the s o l i d state i s very i n t r i g u i n g . A possible explanation (mostly speculative) can be thought of i n terms of t r i p l e t - t r i p l e t a n n i h i l a t i o n i n which two t r i p l e t s of 5 a n n i h i l a t e to produce a s i n g l e t excited state and a ground state (Scheme 19). The s i n g l e t excited state thus formed may react photochemically to give the cyclooctatetranene d e r i v a t i v e ( 6 ) . T r i p l e t - t r i p l e t a n n i h i l a t i o n (TTA) i s a well known phenomenon i n the photophysics of aromatic molecules (both i n s o l u t i o n and the s o l i d state) and i s one of the mechanisms proposed to explain delayed f l o u r e s c e n c e ^ , but as f a r as the author i s aware no photochemical r e a c t i o n r e s u l t i n g from the TTA process has been reported i n the l i t e r a t u r e . To explain the r e s u l t s obtained i n the s e n s i t i z e d photo-l y s i s of 5 , the TTA process may be suggested and i s e n t i r e l y based on the assumption that 6 i s formed v i a the excited s i n g l e t state. Various processes that may be occurring i n the s e n s i t i z e d photolysis of 5 -53-are shown i n Scheme 19 (several other r a d i a t i v e and non-radiative d e a c t i v a t i o n processes of the excited states occur but are not shown). When the (presumed) s o l i d s o l u t i o n of 5 containing 1% xanthone i s i r r a d i a t e d at 337 nm, the s e n s i t i z e r i s excited to i t s s i n g l e t excited l [ X ] 3 3 7 n m > l [ X ]* 1[ X ]* _LS£ 3, x j * '[ X ]~ + 1 [ 5 ] -22222 L [ X ] + 3 [ 5 }* transfer 3[ 5 ] * di-7r.CH 4 > 1[ 7 ] + l[ 8 ] 3 [ 5 ]* + 3 [ 5 ]* —LL± - 1[ 5 ]* + 1[ 5 ![ 5 ]* ^ 1 [ 6 ] Scheme 19 state, which quickly and e f f i c i e n t l y intersystem crosses to i t s t r i p l e t e x cited s t a t e . ^ Then energy transfer to the s i n g l e t ground state of 5 occurs to produce the t r i p l e t excited state of 5. The t r i p l e t of 5 thus formed may undergo photochemical decay to the di-jr-methane re a c t i o n products 7 and 8, or through i n t e r a c t i o n with another t r i p l e t of 5, may give r i s e to a s i n g l e t excited state and a ground state of 5. The - 5 4 -s i n g l e t e x c i t e d s t a t e of 5 thus formed may decay photochemically to product 6 . TTA i s a b i m o l e c u l a r process and depends on the p r o b a b i l i t y of encounter of two t r i p l e t s to give a s i n g l e t e x c i t e d s t a t e and a ground s t a t e . That means the l i f e t i m e of the t r i p l e t e x c i t e d s t a t e should be long enough to encounter another t r i p l e t before other d e a c t i v a t i o n modes quench the t r i p l e t to ground s t a t e . In d i l u t e s o l u t i o n s , the concentra-t i o n of t r i p l e t s i s low, and a l s o the l i f e t i m e of the t r i p l e t i s expected to be lower than i n r i g i d media because of higher r a t e s of d e a c t i v a t i o n of the t r i p l e t e x c i t e d s t a t e . Consequently, the process of TTA i s u n l i k e l y i n the s o l u t i o n phase s e n s i t i z e d p h o t o l y s i s r e s u l t s , where the s i n g l e t product i s obtained only i n a t r a c e amount (Table 6 ). In r i g i d media, l i k e g l a s s y s o l u t i o n s at 7 7 K or c r y s t a l l i n e environments, owing to the r i g i d i t y of the medium, the l i f e - t i m e s of t r i p l e t s are u s u a l l y longer than i n s o l u t i o n . A l s o due to the r i g i d i t y , the e x c i t e d t r i p l e t s cannot d i f f u s e and hence the process of TTA occurs through e x c i t o n m i g r a t i o n and depends on the p r o b a b i l i t y of having two t r i p l e t s p laced next to each other. During the process of e x c i t a t i o n energy hopping, i f two e x c i t e d t r i p l e t s are formed next to each other, they may i n t e r a c t through an encounter p a i r (probably an excimer) and r e d i s t r i b u t e t h e i r energy to give a s i n g l e t e x c i t e d s t a t e and a ground s t a t e . Thus, TTA i s more probable i n the c r y s t a l l i n e medium because of higher concentrations and longer l i f e t i m e s of the t r i p l e t s , and i n the case of 5 may e x p l a i n the formation of s i n g l e t product i n the s e n s i t i z e d p h o t o l y s i s i n the s o l i d s t a t e . One important question that now a r i s e s i s why the s i n g l e t e x c i t e d -55-s t a t e formed upon d i r e c t i r r a d i a t i o n i n the pure s o l i d s t a t e does not r e a c t photochemically, whereas the s i n g l e t e x c i t e d s t a t e formed v i a TTA when s e n s i t i z e d i n the s o l i d s t a t e i s able to decay to the product 6 . The answer may l i e i n the f a c t that a d d i t i o n of the s e n s i t i z e r has d i s -rupted the l a t t i c e to permit the s i n g l e t e x c i t e d s t a t e to r e a c t photo-c h e m i c a l l y . However, p h o t o l y s i s of a sample prepared by c o - c r y s t a l l i z i n g a mixture of 5 and adamantane (6% mol/mol) from the melt gave r e s u l t s s i m i l a r to those obtained i n the pure s o l i d s t a t e . Adamantane was chosen because of d i f f e r e n c e i n s t r u c t u r e from 5 and because i t i s expected to d i s t u r b the l a t t i c e of the host. Another p o s s i b i l i t y i s that TTA may l e a d to the formation of a higher s i n g l e t e x c i t e d s t a t e , which r e a c t s photochemically to product 6 much f a s t e r than i t undergoes i n t e r n a l conversion to the lowest s i n g l e t e x c i t e d s t a t e . Involvement of higher s i n g l e t e x c i t e d s t a t e i n a photochemical r e a c t i o n has been suggested e a r l i e r f o r a system s i m i l a r to the present o n e . ^ Thus, i t i s not c l e a r whether there i s any d i f f e r e n c e i n the nature of s i n g l e t e x c i t e d s t a t e s formed upon d i r e c t i r r a d i a t i o n and that formed by TTA, or the formation of s i n g l e t product i s favored due to the l a t t i c e disturbance. More work needs to be done before some concrete answers can be obtained to e x p l a i n what a c t u a l l y i s happening i n the s e n s i t i z e d p h o t o l y s i s of 5 i n the s o l i d s t a t e . An examination of the r e s u l t s given i n Table 6 a l s o shows th a t the product r a t i o s observed i n c r y s t a l s are d i f f e r e n t from those observed i n KBr p e l l e t s , an important d i f f e r e n c e being that more s i n g l e t product i s obtained when p h o t o l y s i s was c a r r i e d out i n a KBr p e l l e t . This may -56-suggest e i t h e r one or both of the f o l l o w i n g : (1) There i s a chemical e f f e c t of the KBr matrix on the photochemical r e a c t i o n , or (2) There i s an e f f e c t of pressure ( a p p l i e d during the process of making the KBr p e l l e t ) on the photochemical r e a c t i o n . E f f e c t o f K B r M a t r i x on P h o t o l y s i s o f 5 An e f f e c t of the KBr matrix may be expected due to the presence of a heavy atom, Br.^^ I t i s known that an e x t e r n a l heavy atom has v a r y i n g e f f e c t s on d i f f e r e n t p hotophysical processes ( f o r expample, enhanced inter s y s t e m c r o s s i n g ) . ^ > ^ 1 In t h i s case the e x t e r n a l heavy atom may be expected to p l a y a r o l e i n enhancing the TTA process, consequently l e a d i n g to more s i n g l e t product when the p h o t o l y s i s i s c a r r i e d out i n a KBr p e l l e t . This can be supported by the f a c t that the TTA of anthra-cene t r i p l e t s enhanced by solvents c o n t a i n i n g heavy atoms has been reported r e c e n t l y . The r e s u l t s of i r r a d i a t i o n s i n a KBr matrix without s e n s i t i z e r and a l s o the r e s u l t s of p h o t o l y s i s of pure p e l l e t s of 5 are given i n Table 7 . I t can be seen i n Table 7 that s i n g l e t product 6 i s obtained i n higher q u a n t i t i e s i n the p h o t o l y s i s of pure p e l l e t s of 5 and a l s o i n a KBr p e l l e t , but the r a t i o s obtained when powdered mixtures -57-Sample Photoproducts (%) 6 7 8 (5+KBr) Powder 3 51 46 ±2 (5+KBr) Pellet 36 16 48 ±3 Pure Pellet of 5 15 15 70 ±1 Table 7 : Results showing the effect of KBr matrix and that of pressure on the photoproduct ratios. of 5 and KBr are photolysed are similar to those observed for powder-ed samples of pure 5. These results seem to suggest a chemical effect of pressure on the photolysis of 5 in the solid state in producing more singlet product 6. E f f e c t of Pressure on the Photolysis of 5 i n the S o l i d State To determine i f there is any effect of pressure on the photolysis of 5 in the solid state, finely powdered samples of 5 were pressed at different pressures and the pellets thus obtained were then photolysed. Wan et al.,^° in 1965, reported the photodimerization of anthracene and 9-anthraldehyde in KBr pellets pressed at different pressures, in which the authors also noted that a "pellet" technique would be a simple and convenient method for qualitative study of the effect of pressure on - 5 8 -s o l i d s t a t e c h e m i c a l r e a c t i o n s . The r e s u l t s o b t a i n e d i n t h e p r e s e n t s t u d y a r e g i v e n i n T a b l e 8 . The p e r c e n t o f s i n g l e t p r o d u c t 6 o b t a i n e d a g a i n s t t h e p r e s s u r e a p p l i e d i n c r e a s e s s h a r p l y b e t w e e n 4 , 0 0 0 and 5 , 0 0 0 l b s . , and r e m a i n s a p p r o x i m a t e l y c o n s t a n t t h e r e a f t e r r e g a r d l e s s o f t h e amount o f p r e s s u r e a p p l i e d t o make t h e p e l l e t . I t was e x p l a i n e d e a r l i e r t h a t t h e f o r m a t i o n o f 6 i n o n l y t r a c e amounts i n P r e s s u r e A p p l i e d P h o t o p r o d u c t s (%) ( i n l b s c m - 2 ) 6 7 8 4 , 0 0 0 5 33 62 ± 1 5 ,000 13 25 62 ± 4 1 0 , 0 0 0 13 27 60 ± 1 1 5 , 0 0 0 19 19 62 ±2 2 0 , 0 0 0 17 26 57 ±2 T a b l e 8 : R e s u l t s s h o w i n g the e f f e c t o f p r e s s u r e on t h e p h o t o -p r o d u c t r a t i o s o f 5 i n t h e s o l i d s t a t e . i n t h e s o l i d s t a t e p h o t o l y s i s i s p r o b a b l y due t o t h e d i f f i c u l t y ( s t e r i c h i n d r a n c e i m p o s e d by t h e i n t e r m o l e c u l a r p a c k i n g i n t h e c r y s t a l l a t t i c e ) o f f o r m a t i o n o f t he [2+2] a d d u c t i n t he s o l i d s t a t e ( s ee p 3 9 ) . The f o r m a t i o n o f g r e a t e r amounts o f 6 a t h i g h e r p r e s s u r e s seems t o be i n a c c o r d w i t h t h e g e n e r a l p r e d i c t i o n t h a t t h e more s t e r i c a l l y h i n d e r e d a r e a c t i o n i s , t h e more i t w i l l be a c c e l e r a t e d a t h i g h p r e s s u r e s , t h e b a s i s on w h i c h Wan e t a l . have e x p l a i n e d t h e i r -59-results, where the quantum yield of photodimerization of anthracene decreases with increase in pressure applied and that of 9-anthralde-hyde increases with increase in pressure applied to make the pellet. It may also be true that the formation of 6 is favored at defect sites, and the number of such sites at ambient conditions is smaller, but may be expected to be higher at higher pressures. Thus, the amount of 6 formed in the solid state might be expected to be higher at higher pressures. A change in the product ratios could also be expected i f there were any phase transition in the solid state due to the pressure applied. Thus, i t may be that when sensitized samples are photolysed in KBr pellets, the effect of the external heavy atom and the effect of pressure are adding to the TTA process to give more singlet product than when the sensitized sample is irradiated in crystalline form (Table 6) . Another difference observed between irradiation of sensitized samples in crystalline form and in KBr pellets is that the rate of reaction is found to be relatively high in the case of a KBr pellet, i.e., the percent conversion versus time of irradiation is high. The difference in the rates may be due either to the KBr matrix or.the effect of pressure. Several irradiation results summarized in Table 9, indicate that the rate of the reaction is unaffected by pressure, and that the KBr matrix seems to play a dominant role in enhancing the rate of photochemical reaction of 5, both when sensitized and unsensitized. This may also -60-Sample Time of I r r a d i a t i o n (hours) % Conversion to Products Lamp Source UNSENSITIZED (5+KBr) Powder 23 30 Hanovia (5+KBr) P e l l e t 17.5 40 Pure P e l l e t of 5 19.5 3.5 SENSITIZED Crystals 0.5 1 N2 Laser KBr P e l l e t 0.5 20 tt Table 9 : Several i r r a d i a t i o n r e s u l t s showing the e f f e c t of KBr matrix on the rate of photolysis of 5 . be due to the external heavy atom e f f e c t which i s known to enhance the rates of a l l s i n g l e t - t r i p l e t and t r i p l e t - s i n g l e t processes to varying degrees. ^ 1 -61-Dlscusslon of the C r y s t a l Structure of Compound 5 The details of data collection and analysis are given in the experimental section and are also summarized in Table 10. The f i n a l positional, and thermal parameters are given in Tables 1 and 2 of the appendix; bond lengths, bond angles, and torsion angles along with their estimated standard deviations are given in Tables 3-7 of the Appendix. The crystal contains two molecules per asymmetric unit, with nearly identical structures and conformations. Bond lengths, bond angles, and torsion angles of both molecules in the asymmetric unit are not significantly different from each other, or from normal values. There is rough pseudo-symmetry, with the two molecules in the asymmetric unit related by an approximate glide plane at z=l / 2 . -62-c r y s t a l system t r i c l i n i c space group P i a (A) 16.1642(15) b (A) 14.7470(13) c (A) 8.3073(6) a (deg) 90.855(69) P (deg) 112.821(56) 7 (deg) 108.736(83) V (A 3) 1706.30(27) Z 4 D c (g cm - 3) 1.302 F(000) 704 ft (Cu K Q) (cm" 1) 6.92 c r y s t a l dimensions (mm) 0.4x0.4x0.2 t r a n s m i s s i o n f a c t o r 0.801-0.912 scan type u-29 scan range (deg i n w) O.75+O.14tan0 scan speed (deg m i n - 1 ) 10.0 data c o l l e c t e d ±h, +k, ±1 2«max <deS> 150 c r y s t a l decay n e g l i g i b l e unique r e f l e c t i o n s 7008 r e f l e c t i o n s w i t h I>3a(I) 4292 number of v a r i a b l e s 452 R 0.066 Rw 0.084 S 3.047 mean A/a ( f i n a l c y c l e ) 0.001 max A/a ( f i n a l c y c l e ) 0.004 r e s i d u a l d e n s i t y (e A - 3 ) 0.87 Temperature 295 K, Enraf-Nonius CAD4-F d i f f r a c t o m e t e r , Cu-K a r a d i a t i o n ( A K a l = 1.540562, A K a 2 = 1.544390 A), graphite monochromator, t a k e o f f angle 2.7°, aperture (2.0 + tan 6) x 4.0 mm at a distance of 173 mm from the c r y s t a l , scan range extended by 25% on both sides f o r background measurement, CT2(I) = C + 2B + [0.04(C-B)] 2 (C=scan count, B=normalized background count), f u n c t i o n minimized: 2 " ( | F 0 | - | F C | ) 2 where w - 1 / ^ 2 ( F ) , R = S||F |- F J | / S T F O | , R W = [ S w ( | F 0 | - | F c | ) 2 / 2 w | F 0 | 2 ] 1 / 2 ( s _ [SW(JF O - J F C | ) 2 / ( m - n ) ] V 2 . Values given f o r R, R^, and S are based on those r e f l e c t i o n s w i t h I>3a(I). Table 10 : Data c o l l e c t i o n parameters and c r y s t a l l o g r a p h i c r e s u l t s obtained. Compound 5, i n the s o l i d state, i s locked into a conformation such that the two ester groups are non-equivalent, and thus the average mirror plane of symmetry present i n the s o l u t i o n phase (as shown by the ^ C NMR spectrum i n solution) i s destroyed. Stereo-scopic views (ORTEP diagrams) of the conformations of molecules 1 and 2 are given i n Figures 6 and 7 r e s p e c t i v e l y ; and a packing diagram i s given i n Figure 8 . Figure 6 : ORTEP diagram of molecule 1. Figure 7 : ORTEP diagram of molecule 2. -64-Figure 8 : Packing diagram of compound 5 . The conformation adopted by th i s compound i n the s o l i d state i s quite comparable to that of two other dibenzobarrelene d i e s t e r s (compounds 10 and 11 *, Figure 9), i n that one of the two ester carbonyl groups i s more conjugated with the C=C double bond than the 10<R = H 11 RsCI Figure 9 : Two dibenzobarrelene d i e s t e r s c l o s e l y r e l a t e d to 5. * : C r y s t a l structures of compounds 10 and 11 were solved by Fred C. Wireko and V i v i a n Yee respectively. other. Crystallographic parameters of photochemical interest in the present study are the torsion angles involving the carbon atoms of the ethylenic bond and a carbonyl group, defined as c6^  and <f>2 in Figure 10. These torsion angles give the mean deviation of the plane of the carbonyl group from that of the ethylenic bond, which in turn is a measure of the extent of conjugation of the carbonyl group with R = Me Figure 10 : Torsion angles involving carbon atoms of the central double bond and the carbonyl groups. the ethylenic group. The closer the values of these torsion angles are to 0°, the more conjugation. An examination of these torsion angles of both the molecules in the asymmetric unit (Table 11) indicates that the carbonyl groups involving 02 (for molecule 1) and 02' (for molecule 2) are conjugated with the ethylenic bond, whereas the other carbonyl group is essentially non-conjugated. This is of importance because only one of the two possible cyclopropyldicarbinyl -66-* 1 (degrees) Molecule 1 1 . 9 91.7 Molecule 2 2.4 -91.4 Table 11 Torsion angles <f>^ and <f>2 of both the molecules in the asymmetric unit. diradicals in the conversion of compound 5 to the corresponding t r i p l e t products 7 and 8 w i l l be stabilized by conjugation through the carbonyl group. In this case, the carbonyl group on the side opposite to the bridgehead methyl substituent is more conjugated with the central C=C double bond. Thus, i t is reasonable to assume that biradical BR-8 is more stable than BR-7 (Scheme 16, p 34), thus explaining the major product in the solid state. In this context, i t is also important to look at the free space around the two ester moities which is needed, in the f i r s t place, to allow the i n i t i a l vinyl-benzo bond formation to give the biradicals, BR-7 and BR-8. No intra- or intermolecular energy calculations were performed, and so i t is not known what is the relative effect on the lattice energy in moving one ester group compared to the other dur-ing the i n i t i a l vinyl-benzo bond formation. From the examples which have already been investigated in our laboratory, 3^ i t is known that the packing effect of the crystal lattice dominates the electronic effect in cases where there is a competition between the two. Thus, -67-i n t h i s case i t i s reasonable to assume that the packing e f f e c t s may also support the formation of compound 8 as a major product (which i s supported by e l e c t r o n i c factors) i n the s o l i d state. Discussion on the Minor Disorder of the Structure The presence of minor disorder i n the positions of one of the carbomethoxy groups of each molecule i n the asymmetric u n i t was sug-gested by small r e s i d u a l electron density peaks (maximum 0.87 eA - 3) present i n the f i n a l Fourier difference map. The type of disorder known f o r carbomethoxy groups i s that two orientations are possible which are separated by a 180° r o t a t i o n (Figure 11),^ 3 with the carbo-Figure 11 : Two possible orientations of a carbomethoxy group separated by 180°. -68-methoxy groups of some molecules of the l a t t i c e oriented i n one d i r e c t i o n , whereas the remainder of the molecules have t h e i r carbo-methoxy groups oriented i n the other sense. Since an average structure of the molecule over the en t i r e l a t t i c e i s seen by X-rays, the p o s i t i o n of the carbomethoxy group w i l l appear as disordered between the two possible o r i e n t a t i o n s . With t h i s idea i n mind, an attempt was made to solve the disor-der i n the postions of the carbomethoxy groups of both the molecules by a s p l i t atom model,^ 3 i n which some of the r e s i d u a l e l e c t r o n density peaks on the dif f e r e n c e map were included as atoms of a new carbomethoxy group which i s d i f f e r e n t l y oriented and the occupancies were d i s t r i b u t e d between the s p l i t atoms (80:20). The structure was then r e f i n e d further allowing i s o t r o p i c thermal motion of the s p l i t atoms while the r e s t of the atoms were f i x e d i n t h e i r p o s i t i o n s . The values of the i s o t r o p i c thermal parameters of the s p l i t atoms were reasonable, while the value of R-factor increased s l i g h t l y , and e s p e c i a l l y the new atoms of the disordered groups (of both molecules 1 and 2 ) d i d not make a reasonable geometry within themselves or with the r e s t of the molecule. Several attempts to s p l i t the atoms i n d i f f e r e n t ways did not help i n solv i n g the nature of the disorder. In another attempt, a l l atoms of the disordered carbomethoxy groups of both the molecules were removed (R-factor = 0.349) and elec t r o n density contour maps of the difference Fourier synthesis were obtained. Sections of the contour maps where atoms of the d i s -ordered groups are located were c a r e f u l l y examined. But no new information was obtained which could suggest a possible s o l u t i o n f o r the disorder. Thus, i n the end, the structure was l e f t at the R-factor = 0.066, with the minor disorder unresolved. -70-EXPERIMENTAL Photochemical Work General M e l t i n g P o i n t s . M e l t i n g p o i n t s were obtained on a Fisher-Johns m e l t i n g p o i n t apparatus and are not co r r e c t e d . I n f r a r e d Spectra. IR sp e c t r a i n chloroform were recorded on a P e r k i n -Elmer 710 B i n f r a r e d spectrophotometer and were c a l i b r a t e d u s i n g the 1601 cm"l band of polystyr e n e . A Perkin-Elmer 1710 F o u r i e r Trans-form i n f r a r e d spectrometer was used f o r o b t a i n i n g s p e c t r a i n KBr p e l l e t or neat form; KBr p e l l e t s contained 2-3 mg of sample and 150-175 mg of KBr and were made u s i n g a Perkin-Elmer evacuated d i e 186-0002 and a Carver l a b o r a t o r y press model B. Spectra of neat samples were obtained by p r e s s i n g o i l s between sodium c h l o r i d e p l a t e s . Nuclear Magnetic Resonance Spectra. A l l ^ H NMR and ^ -3C NMR spec-t r a were recorded on a V a r i a n XL-300 spectrometer at 300 and 75.4 MHz r e s p e c t i v e l y . The ^H NMR N.O.E. d i f f e r e n c e spectrum f o r com-pound 6 was recorded on a Bruker WP-400 (400 MHz) spectrometer. Deuterochloroform was the solvent used f o r a l l s p e c t r a . S i g n a l p o s i -t i o n s are reported i n terms of S, p a r t s per m i l l i o n downfield from t e t r a m e t h y l s i l a n e , which was the i n t e r n a l standard used. M u l t i p l i c i t y , number of protons and assignment are given i n parentheses f o l l o w i n g S. For 1 3C NMR s p e c t r a , the s i g n a l s were assigned ( c r y s t a l l o g r a p h i c num-bering of the C atoms was followed) based i n part on the attached pro-ton t e s t (APT). Mass Spectra. Both low r e s o l u t i o n and high r e s o l u t i o n mass spectra were recorded on a Kratos MS 50 mass spectrometer. A Kratos MS 80 mass spectrometer coupled with a Karlo-Erba gas chromatograph was used for GC-MS study. U l t r a v i o l e t Spectra. The UV spectrum of compound 5 i n methanol was recorded on a Perkin-Elmer 552 A UV-VIS spectrophotometer. UV-VIS spectra i n the s o l i d state (KBr p e l l e t ) were recorded on a Cary-17 D spectrophotometer. The KBr p e l l e t contained 1-2 mg of the tes t sample and 150-160 mg of KBr. A blank KBr p e l l e t was used as reference. The p e l l e t s were made as described for IR spectroscopy. Both p e l l e t s were held i n p e l l e t holders with quartz windows and were evacuated using a laboratory vacuum pump. Absorption maxima (^ m a x) are given i n nanometers (nm). Molar a b s o r p t i v i t i e s expressed as L mole" 1 cm"1 i n the case of the spectrum obtained i n methanol are given i n parentheses. Elemental An a l y s i s . Elemental analysis reported was done by Mr. P. Borda, the departmental analyst. Gas Chromatography. A Hewlett-Packard 5890 A c a p i l l a r y gas chroma-tograph attached to a Hewlett-Packard 3392 A integrator was used for a l l a n a l y t i c a l gas chromatographic analyses. D e t a i l s of the conditions -73-are given below. A l l r e t e n t i o n times (RT) reported are i n minutes. Column type: DB-1 ; 15 m i n length and 0.25 /xm i n thickness. Column head pressure: 15 p s i . Program: 200°C; isothermal. Column Chromatography. For p u r i f i c a t i o n and separation purposes, s i l i c a gel 60 (230-400 mesh, E. Merck) was used i n column chromatograhpy. Chemicals and Solvents. 9-Methylanthracene obtained from Exciton Chemical Co., Inc. and dimethyl acetylenedicarboxylate from A l d r i c h Chemical Co., Inc. were used as received. A l l solvents were obtained from BDH Chemicals. For preparative photolyses, f r e s h l y d i s t i l l e d ace-tone and thiophene-free benzene were used; for product r a t i o determina-tions, acetone (BDH s p e c t r a l grade), thiophene-free benzene and acetoni-t r i l e (BDH s p e c t r a l grade which was further dried) were used. Ace-t o n i t r i l e was dr i e d by r e f l u x over CaH 2 followed by f r a c t i o n a l d i s -t i l l a t i o n . - * ^ Thiophene-free benzene was prepared by washing with concentrated sulphuric acid, water, d i l u t e sodium hydroxide and then again with water followed by drying with ?2®5 a n a d i s t i l l a t i o n . - ^ A l l other solvents were used as received. Photolysis Procedures. Unless otherwise mentioned, a l l a n a l y t i c a l and preparative photolyses were performed using a Hanovia 450 W medium pressure mercury lamp placed i n a water-cooled Pyrex immersion well (thickness = 4 mm, transmits A > 290 nm). In addition, for a n a l y t i c a l -74-photolyses when s e n s i t i z e d , a Molectron UV 22 pulsed N 2 Laser (A = 337 nm, pulse r a t e = 20-30 per min) or a Hanovia lamp w i t h a uranium g l a s s f i l t e r ( t h i c k n e s s = 2 mm, transmits A > 340 nm) were used. A l l photolyses were performed at room temperature. Each a n a l y t i c a l photo-l y s i s sample was analysed by GC at l e a s t twice c o n s e c u t i v e l y . SYNTHESIS P r e p a r a t i o n of Dimethyl 9,10-dihydro-9-methyl-9,10-ethenoanthracene-11,12-dicarboxylate (Compound 5 ) . 3 ^ ' ^ ^ In a 100 mL round bottomed f l a s k f i t t e d w i t h a r e f l u x condenser and a dry tube, 5.03 g (26.1 mmoles ) of 9-methylanthracene and 3.91 g (27.5 mmoles, 5.4% excess) of dimethyl a c e t y l e n e d i c a r b o x y l a t e were placed. The f l a s k and i t s contents were heated i n an o i l bath at 180°C f o r 1.5 h r s . The t h i c k brown l i q u i d obtained was l e f t overnight at room temperature and the s o l i d residue obtained d i s s o l v e d i n about 50 mL of hot chloroform. Then about 10 mL of ethanol was added and the s o l u t i o n s et aside to c r y s t a l l i z e . The c r y s t a l l i n e m a t e r i a l thus obtained (7.5 g, 85% y i e l d ) was washed w i t h s e v e r a l 5 mL p o r t i o n s of ethanol u n t i l the c r y s t a l s were white. This m a t e r i a l was r e c r y s t a l l i z e d from a 40:60 mixture of ethanol and chloroform to give 6.6 g (75% y i e l d ) of n i c e r e c t a n g u l a r c r y s t a l s of compound 5. MP: 181-182°C ( l i t e r a t u r e mp: 180°C). -75-IR (KBr p e l l e t ) : 1728 (a,0 -unsaturated e s t e r carbonyl s t r e t c h ) , 1640 (C=C s t r e t c h ) cm"1. 1H NMR: S, 2.18 ( s , 3H, bridgehead methyl hydrogens), 3.76 and 3.83 ( s , 3H, e s t e r methyl hydrogens), 5.67 (s, IH, bridgehead hydrogen), 7.02-7.10 (m,4H, aromatic) and 7.28-7.44 (m, 4H, aromatic). 1 3 C NMR: 5, 12.28 (C13), 50.04 (C9), 51.48 (C10), 52.19 and 52.35 (015,017). 121.06, 123.57, 125.04, 125.23 (C1-C8), 145.45, 145.64 (011,012), 141.96, 155.54 (C4a,C8a,C9a,C10a), 163.79, 167.42 (014,016). UV (methanol): X m a x (n -+ ix*): 270 (1468), 278 (1651), and a shoulder at 294 (625). UV (KBr p e l l e t ) : A m a x (n •+ n*): 271, 279, and a shoulder at 295. MS: m/e ( r e l a t i v e i n t e n s i t y ) : 334 (M +, 21.8), 320 (2.9), 302 (24.6), 274 (100), 260 (8.8), 243 (20.3), 231 (8.8), 215 (96.9), 192 (18.5). Exact mass c a l c u l a t e d ( C 2 1 H 1 8 0 4 ) : 334.1205 ; measured: 334.1212. Elemental A n a l y s i s : ( C ^ H ^ O ^ c a l c u l a t e d : C, 75.43 ; H, 5.43. found: C, 75.16 ; H, 5.28. PHOTOCHEMISTRY OF COMPOUND 5 P r e p a r a t i v e P h o t o l y s i s of Compound 5 i n Acetone.35 Compound 5 (0.55 g, 1.6 mmoles) was d i s s o l v e d i n 100 mL of acetone and N 2 gas was bubbled through the s o l u t i o n f o r 0.5 hr. Then the s o l u t i o n was i r r a d i a t e d u s i n g a Hanovia 450 W medium pressure lamp through a Pyrex f i l t e r f o r 1 hr; N 2 gas was passed through the s o l u t i o n -76-throughout the photolysis. The reaction mixture analysed by GC d i d not show any s t a r t i n g material, but had three peaks with r e t e n t i o n times 7.7 min (73% area), 8.4 min (12% area) and 8.7 min (11% area). Acetone was removed under reduced pressure to give a yellow o i l which weighed 0.66 g. This o i l was dissolved i n chloroform, and s i l i c a gel was added to make a s l u r r y . The s l u r r y was then added to the top of an already packed s i l i c a gel column (15 cm x 2 cm). The column was eluted with a mixture of 2% (V/V) e t h y l acetate i n petroleum ether to give f i r s t f r a c t i o n s with gas chromatographic RT's 8.4 and 8.7 min and then f r a c t i o n s with RT 7.7 min. The purest f r a c t i o n s c o l l e c t e d , upon removal of solvent, gave o i l s i n each case. To the o i l with RT 7.7, a few mL of d i e t h y l ether were added and the walls of the con-tai n e r were scratched to obtain a s o l i d (compound 7) which weighed 245 mg (44% y i e l d , > 95% pure). This s o l i d was further p u r i f i e d by r e c r y s t a l l i z a t i o n from chloroform-ethanol mixture. Similar attempts f a i l e d i n the case of the o i l with RT's 8.4 and 8.7 min (compound 8, i t was assumed that t h i s compound i s decomposing on the GC column to show two peaks, see p 31) which weighed 134 mg (24% y i e l d , >90% pure). A l l the remaining f r a c t i o n s containing both the photoproducts were mixed together and evaporation of the solvent gave an o i l weigh-ing 160 mg. Preparative Photolysis of Compound 5 i n Benzene. Compound 5 (1.0 g, 3.0 mmoles) was dissolved i n 100 mL of benzene (thiophene-free) and N 2 gas was bubbled through the s o l u t i o n for 0.5 hr. Then the s o l u t i o n was i r r a d i a t e d using a Hanovia 450 W medium pressure lamp through a Pyrex f i l t e r f o r 8.5 hr under a N 2 atmosphere. The photolysis mixture when analysed by GC, showed peaks with RT's 5.9 (34% area), 7.6 (35% area), 8.3 (7% area), 8.6 (10% area) and 9.3 min ( s t a r t i n g material, 13% area). Rotary evaporation of benzene gave a yellow residue (1.1 g) which was d i s s o l v e d i n ethanol. Rapid cooling using l i q u i d nitrogen gave a yellow p r e c i p i t a t e (157 mg), which was f i l t e r e d under suction. The p r e c i p i t a t e when analysed by GC, d i d not show any of the peaks corresponding to s t a r t i n g material or photoproducts, whereas the f i l t r a t e had shown peaks with RT's 6.2 (31% area), 7.9 (37% area), 8.5 (9% area), 8.8 (9% area), and 9.6 min (14% area). Removal of the solvent from the f i l t r a t e gave an o i l (0.9 g), which was chromatographed on a s i l i c a gel column (15 cm x 2 cm). When eluted with 5% (V/V) ethyl acetate i n petroleum ether, a l l the three photoproducts moved together. However, the photoproduct with RT 6.0 ( s i n g l e t product, compound 6) was separated i n 85% p u r i t y (as determined by GC). Removal of the solvent from the concerned f r a c t i o n s under vacuum gave an o i l (63 mg, 6% y i e l d ) . The p u r i t y was improved to 90% (as determined by GC) by chromatographing again on a s i l i c a gel column. Preparative Photolysis of Compound 5 In the S o l i d State. Compound 5 (0.46 g, 1.4 mmoles) was dissolved i n a minimum amount of d i e t h y l ether and chloroform mixture i n a three-necked photolysis v e s s e l which can hold a quartz immersion well containing a Hanovia 450 W medium -78-pressure lamp. The so l v e n t mixture was evaporated s l o w l y i n such a way as to produce a t h i n l a y e r of c r y s t a l s of compound 5 on the i n s i d e w a l l s of the c o n t a i n e r . N 2 gas was passed over the c r y s t a l s f o r 0.75 hr, and they were then photolysed from w i t h i n through a quartz f i l t e r f o r 48 h r . The conversion as shown by GC was 10%. The c r y s t a l s d i d not show any m e l t i n g but were turned to an intense y e l l o w c o l o u r . The c r y s t a l s were washed w i t h small p o r t i o n s (5 mL) of d i e t h y l ether to remove most of the photoproducts ( s t a r t i n g m a t e r i a l i s s p a r i n g l y s o l u b l e i n d i e t h y l e t h e r ) . The remaining s t a r t i n g m a t e r i a l on the w a l l s of the co n t a i n e r was f u r t h e r photolysed f o r 8 hr. At the com-p l e t i o n of p h o t o l y s i s , the e a r l i e r p o r t i o n s of d i e t h y l ether and the f r e s h p h o t o l y s i s mixture were d i s s o l v e d i n 10% (V/V) chloroform i n d i e t h y l ether, and the s o l u t i o n was allowed to evaporate s l o w l y . Most of the s t a r t i n g m a t e r i a l c r y s t a l l i z e d out and was separated by s u c t i o n f i l t r a t i o n . The f i l t r a t e upon removal of so l v e n t by r o t a r y evaporation gave an o i l (330 mg) which showed 15% (compound 6 ), 9% (compound 7), 30% (compound 8) and 37% ( s t a r t i n g m a t e r i a l ) when analysed by GC. S i l i c a g e l column chromatography of the o i l u s i n g 2% (V/V) e t h y l acetate i n petroleum ether gave 29 mg of compound 8 (98% pure, 16% y i e l d ) . C h a r a c t e r i z a t i o n of the Photoproducts Dimethyl 4b,8b,8c,8d-tetrahydro-4b-methyldibenzo[a,f]cyclopropafcd]-pentalene-8c,8d-dicarboxylate (Compound 7 ) : 3 ^ -79-MP: 125-127°C ( l i t e r a t u r e mp: 1 7 8 8 C ) . " IR (KBr p e l l e t ) : 1734, 1712 (ester carbonyl stretches) cm"1. 1 H NMR: 6, 1.92 (s, 3H, methyl hydrogens), 3.73 and 3.86 (s, 3H, ester methyl hydrogens), 4.34 (s, IH, methine hydrogen of the cyclopropane r i n g ) , 7.03-7.16 (m, 7H, aromatic), 7.56-7.62 (m, IH, aromatic). 1 3 C NMR: 5, 15.29 (C13), 49.85 (C9), 52.02 and 52.49 (C15.C17), 53.66, 61.28, 71.14 (C10-C12), 119.29, 119.38, 125.38, 126.63, 127.02, 127.50, 127.56 (C1-C8, two C signals overlapping), 131.94, 134.36, 152.78, 153.24 (C4a,C8a,C9a,C10a), 167.47, 169.24 (C14,C16). MS: m/e ( r e l a t i v e i n t e n s i t y ) : 335 (M+l, 21.0), 334 (M +, 82.8), 306 (27.2), 302 (26.8), 291 (14.7), 274 (98.6), 260 (26.0), 247 (74.7), 243 (44.6), 231 (35.6), 229 (14.6), 215 (100), 202 (32.4), 189 (19.2). Exact mass ca l c u l a t e d ( C 2 i H 1 8 0 4 ) : 334.1205 ; measured: '334.1207. Dimethyl 4b,8b,8c,8d-tetrahydro-8b-methyldibenzo[a,f]cyclopropa[cd]-pentalene-8c,8d-dicarboxylate (Compound 8):3-> O i l (98% pure by GC). IR (neat): 1731 (saturated ester carbonyl stretch) cm"1. L H NMR: S, 2.01 (s, 3H, methyl hydrogens), 3.76 and 3.84 (s, 3H, ester methyl hydrogens), 5.06 (s, IH, methine hydrogen), 7.00-7.28 (m, 8H, aromatic). 1 3 C NMR: S, 14.55 (C13), 29.71, 54.37, 67.20 (C10-C12) , 52.00, 52.42 (C15.C17), 56.38 (C9), 120.86, 121.31, 124.54, 124.70, 126.78, 126.91, 127.65, 127.81 (C1-C8), 135.10, 138.87, 149.47, 150.21 (C4a,C8a,C9a,ClOa), 168.17, 169.20 (C14.C16). -80-MS: m/e ( r e l a t i v e i n t e n s i t y ) : 334 (M +, 8.4), 302 (15.2), 274 (53.6), 242 (24.8), 215 (100), 202 (13.2), 189 (18.6), 107 (8.3), 95 (9.6). Exact mass c a l c u l a t e d (C2]H 1 8°4): 334.1205 ; measured: 334.1208. D i m e t h y l 5 - m e t h y l d i b e n z o [ a , e ] c y c l o o c t e n e - 6 , 1 1 - d i c a r b o x y l a t e (Compound 6 ) : O i l (90% pure by GC). IR (neat): 1710 (a,B -unsaturated e s t e r carbonyl s t r e t c h ) , 1630 (C=C s t r e t c h ) cm"-1. ' 1H NMR: 5, 2.35 ( s , 3H, methyl hydrogens), 3.68 and 3.82 ( s , 3H, e s t e r methyl hydrogens), 7.03-7.22 (m, 8H, aromatic), 8.07 ( s , IH, v i n y l hydrogen). N.O.E. d i f f e r e n c e experiment: i r r a d i a t i o n of the s i g n a l at 5, 2.35 r e s u l t e d i n enhancement of a s i n g l e t s i g n a l at 6, 3.68 and a doublet centered at S, 7.08. From the N.O.E. d i f f e r e n c e spectrum, i t can be concluded t h a t the v i n y l hydrogen and the v i n y l methyl of the c y c l o o c t a t e t r a e n e are not on the same C=C double bond. 1 3 C NMR: 5, 23.31 (C13), 51.84, 52.32 (C15.C17), 125.98, 126.60, 126.80, 126.99, 127.56, 127.80, 128.67, 129.09 (C1-C8), 130.42, 132.27, 135.11, 136.34, 136.78, 142.80, 148.26 (C10-C12,C4a,C8a,C9a,C10a), 142.60 (C9), 167.02 and 168.25 (C14.C16). MS: m/e ( r e l a t i v e i n t e n s i t y ) : 334 (M +, 10.0), 302 (11.2), 274 (58.2), 243 (18.8), 231 (8.2), 215 (75.6), 202 (9.6), 189 (11.7), 107 (7.0), 94 (10.5). Exact mass c a l c u l a t e d (C21H18O4): 334.1205 ; measured: 334.1203. -81-Comparison of the Product Ratios Determined by -"-H NMR Integration and GC Integration. Compound 5 (15 mg) was dissolved i n 10 mL of acetone, a c e t o n i t r i l e and benzene. Each s o l u t i o n (3 mL) was placed i n a Pyrex v i a l , closed with a rubber stopper and degassed with N 2 gas fo r 15 minutes. Then each sample was photolysed and analysed by GC. The solvents were evaporated and the r e s i d u a l o i l was d r i e d under vacuum. The NMR spectrum f o r each sample was recorded and the methyl resonance signals between S 1.9 and 2.4 ppm (the methyl signals f o r the s t a r t i n g material and the photoproducts are well resolved) were enhanced and integrated. From the i n t e g r a t i o n of the methyl si g n a l s , the percentage of s t a r t i n g material and photproducts was c a l c u l a t e d i n each case, and compared with the GC percent area i n t e g r a t i o n r e s u l t s . The r e s u l t s are given i n Table 2, p 32. I t was assumed l a t e r that compound 8 i s decomposing on the GC column (explained i n the section of Results and Discussion, p 31), and the sum of the integrated areas of peaks with RT's 8.4 and 8 . 7 were added to c a l c u l a t e the percentage of compound 8. Product Ratio Determination: In sol u t i o n: Compound 5 (15 mg) was d i s s o l v e d i n 10 mL of solvent (acetone, a c e t o n i t r i l e and benzene); 0.5 of each s o l u t i o n was placed i n a 3 mm Pyrex tube, degassed by several freeze-pump-thaw cycles and sealed under a N 2 atmosphere. Then each sample was photolysed and anlaysed by GC. The product r a t i o s reported (Table 3,p 36) are s t a t i s t i c a l averages of at l e a s t three a n a l y t i c a l photolyses. The percent conversion of the s t a r t i n g material was kept < -82-15%. In the s o l i d state: P o l y c r y s t a l l i n e and powdered samples (5-10 mg) of compound 5 were placed i n 3 mm Pyrex tubes, degassed and sealed under a N 2 atmosphere. Then the samples were photolysed and ana-lysed by GC. Results are given i n Table 4 , p 39. The diffe r e n c e observed i n the product r a t i o s between the sin g l e c r y s t a l and powder samples l e d to a more systematic study (below) of s o l i d state photolysis of compound 5 . Grinding Experiment. About 2 g of c r y s t a l s of compound 5 were ground using a F r i t s c h P u l v e r i s e t t e Type 00.501, No.506 apparatus. Small amounts of samples were c o l l e c t e d i n v i a l s a f t e r d i f f e r e n t times of grinding. Unground and ground samples were photolysed i n the same way as described above (and also by making sandwiches between two Pyrex plates) and analysed by GC. The r e s u l t s are shown i n the form of a graph i n Figure 2, p 43. Single C r y s t a l Photolysis. A single c r y s t a l (15 mg, colourless) of compound 5 was photolysed under a N 2 atmosphere f o r 24 hr. The c r y s t a l appeared to be as transparent as i t was before the photolysis, but turned yellow. This c r y s t a l was then washed with few drops of d i e t h y l ether, which d i s s o l v e d the uppermost layer of the c r y s t a l leaving the c r y s t a l i n t a c t . The d i e t h y l ether washing removed most of the yellow colour (photolysis mixture) leaving the c r y s t a l opaque (white). The por t i o n of the d i e t h y l ether used for washing was analysed by GC. This -83-process was repeated twice more, each time a n a l y s i n g the p o r t i o n s of the d i e t h y l ether used f o r washing the c r y s t a l . A f t e r the t h i r d washing, the c r y s t a l broke i n t o p i e c e s . F i n a l l y , a l l the p o r t i o n s of the d i e t h y l ether and the remaining c r y s t a l pieces were d i s s o l v e d together and analysed by GC. The r e s u l t s are given i n Table 5 , p 45. UV-VIS Spectrum of the P h o t o l y s i s Mixture of Compound 5 . In S o l u t i o n : Powdered sample (50 mg) of compound 5 was sandwiched between two pyrex p l a t e s and photolysed f o r 48 hr (sample appeared ye l l o w , 11% conversion as shown by GC). The photolysed sample was then d i s s o l v e d i n 10 mL of a c e t o n i t r i l e and a UV-VIS spectrum was recorded on a Cary 17-D spectrophotometer. The spectrum obtained was s i m i l a r to the one obtained i n KBr p e l l e t (below). In the S o l i d S t ate: Compound 5 (1.5 mg) and 157 mg of KBr were ground together and a transparent p e l l e t was made usin g a Carver labo-r a t o r y press model B, as described e a r l i e r f o r IR spectroscopy. A UV spectrum was recorded on a Cary 17-D spectrophotometer as d e s c r i b e d under UV s p e c t r a . The p e l l e t c o n t a i n i n g compound 5 was then photo-l y s e d f o r 20 hr under a N 2 atmosphere ( p e l l e t appeared y e l l o w i n c o l o u r , 90% conversion as shown by GC), and a UV-VIS spectrum was obtained. The r e s u l t s are discussed on p 49. Study of the e f f e c t of Pressure on the P h o t o l y s i s of Compound 5 i n the S o l i d S t a t e . F i n e l y powdered compound 5 was pressed at d i f f e r e n t pressures u s i n g a Carver l a b o r a t o r y press model B. A f t e r p r e s s i n g , the -84-sample appeared as a p e l l e t but was s t i c k y . Each sample was then pho-t o l y s e d (as a p e l l e t or powder) f o r 24 hr under a N 2 atmosphere and analysed by GC. The product r a t i o s reported (Table 8 , p 58) are averages of two runs. A n a l y t i c a l Photolysis i n a KBr Matrix. Compound 5 (5 mg) and 150 mg of KBr were ground together. This powder was used as such f o r pho-t o l y s i s , and was a l s o used to make a KBr p e l l e t as d e s c r i b e d e a r l i e r f o r IR spectroscopy. Both powder and KBr p e l l e t were photolysed and anlaysed by GC. The product r a t i o s reported (Table 7 , p 57) are averages of at l e a s t three photolyses experiments. S e n s i t i z a t i o n Studies i n the S o l i d State. Xanthone was the s e n s i -t i z e r used. 10% (mole/mole) Xanthone i n compound 5 was prepared by c o - c r y s t a l l i z a t i o n from the melt. Compound 5 (0.16 g, 0.48 mmoles) and xanthone (10 mg, 0.05 mmoles) were melted together u s i n g a Bun-sen flame. While molten they were mixed thoroughly by shaking and s w i r l i n g , and allowed to s o l i d i f y . To 7.0 mg of t h i s mixture, 68 mg of compound 5 was added and were melted together as d e s c r i b e d above, and allowed to s o l i d i f y . The s o l i d obtained contained 0.9% (mole/mole) xanthone i n compound 5. The s o l i d sample obtained ( c r y s t a l l i n e ) was photolysed as such and a l s o i n a KBr p e l l e t . The KBr p e l l e t was made as described above f o r the u n s e n s i t i z e d pho-t o l y s i s . The product r a t i o s reported (Table 6,p 52) are averages of at l e a s t three photolyses experiments. -85-C r y s t a l l o g r a p h i c Work C r y s t a l s of compound 5 were grown from ethanol-chloroform mixture by slow evaporation of the solvent system. A f t e r i n i t i a l d i f f i c u l t y i n f i n d i n g a w e l l - d i f f r a c t i n g c r y s t a l , a small c r y s t a l approximately of s i z e 0.4 x 0.4 x 0.2 mm3 was cut from a bigger c r y s t a l and chosen f o r data c o l l e c t i o n by examining p r e c e s s i o n and z e r o - l e v e l Weissenberg photographs. These photographs i n d i c a t e d a t r i c l i n i c u n i t c e l l . Data C o l l e c t i o n The c r y s t a l was mounted on an Enraf-Nonius CAD4-F f o u r - c i r c l e d i f f r a c t o m e t e r i n a random o r i e n t a t i o n . The r e c i p r o c a l space was searched f o r 25 r e f l e c t i o n s u s i n g the program SEARCH. The 25 r e f l e c -t i o n s found w i t h 14.5 < 6 < 21.4 were centered u s i n g another program c a l l e d SETANG. The r e s u l t i n g centered r e f l e c t i o n s were used to con-s t r u c t a p r i m t i v e u n i t c e l l and the corresponding o r i e n t a t i o n matrix. The u n i t c e l l i n d i c a t e d was t r i c l i n i c . This u n i t c e l l was reduced to a Delaunay reduced c e l l and the corresponding o r i e n t a t i o n m a t r i x was c a l c u -l a t e d . The number of molecules per u n i t c e l l , Z was found to be 4 (using an estimated value of 1.3 g cm - 3 f o r the d e n s i t y ) . This i n d i c a t e s two molecules per asymmetric u n i t i f the space group i s PI or four independent molecules per u n i t c e l l i f the space group i s P I , the l a t t e r being c h i r a l . At t h i s stage, exact assignment of the space group was not p o s s i b l e because there are no systematic absences to d i s t i n g u i s h between PI and -86-P l . But the f a c t that there are four molecules per u n i t c e l l indicates a more l i k e l y centrosymmetric space group PI. The data c o l l e c t i o n was then c a r r i e d out with f i l t e r e d Cu K a r a d i a t i o n (A = 1.5418 A) between 0 and 75° 8 using a w-29 scan. n Three nearly orthogonal r e f l e c t i o n s out of the o r i g i n a l 25 centered r e f l e c t i o n s were chosen to check f or i n t e n s i t y and o r i e n t a t i o n period-i c a l l y . The i n t e n s i t i e s of these c o n t r o l l i n g r e f l e c t i o n s were measured every 3600 seconds of X-ray exposure time. Also these r e f l e c t i o n s were checked f or o r i e n t a t i o n a f t e r every 150 r e f l e c t i o n s c o l l e c t e d and reo-r i e n t a t i o n of the c r y s t a l done whenever necessary. Thus, the s t a b i l i t y of the system was monitored and maintained during the data c o l l e c t i o n . A t o t a l of 7008 unique r e f l e c t i o n s with h—20-20, k=0-18, 1—10-10 was c o l l e c t e d . While measuring each r e f l e c t i o n the scan was extended 25% on each side f o r background measurement. Data Processing and Structure Solution Various computer programs used i n the process of sol v i n g the structure are given i n references 57-60. Out of 7008 unique r e f l e c t i o n s c o l l e c t e d , only 4292 r e f l e c t i o n s were considered observed with I/er(I) >3 and were used i n structure determination, a i s ca l c u l a t e d from a 2 ( I ) = S + 2B + [0.04(S-B)] 2 where S = Scan count, B = time-averaged background count. Absorption and Lp (Lorentz and p o l a r i z a t i o n ) corrections were made. The E - s t a t i s -t i c s i n d i c a t e d a centrosymmetric space group PI. The structure was -87-solved by d i r e c t methods using MULTAN80. 450 r e f l e c t i o n s with l a r g e s t E's were used i n MULTAN to generate 64 sets of phase r e l a t i o n s h i p s out of which a set with best combined fig u r e of merit (FOM) gave a l l the non-hydrogen atoms. A l l the non-hydrogen atoms found were r e f i n e d i n i -t i a l l y allowing i s o t r o p i c thermal motion. Then refinement was done allowing anisotropic thermal motion of a l l the non-hydrogen atoms. Hydrogens were then placed i n c a l c u l a t e d positions and the non-hydrogen atoms were r e f i n e d further, r e c a l c u l a t i n g hydrogen atom posit i o n s a f t e r each cycle of refinement. The refinement was done by f u l l - m a t r i x l e a s t -squares method minimizing Ew(|F Q|-|F c|) 2, and Type I i s o t r o p i c e x t i n c t i o n c o r r e c t i o n was applied. A t o t a l of 452 parameters containing 150 posi-t i o n a l parameters, 300 anisotropic thermal parameters, and one parameter each for scale f a c t o r and e x t i n c t i o n c o r r e c t i o n was r e f i n e d and the refinement converged at R = 0.066 and R„ = 0.084 for 4292 observed r e f l e c t i o n s . The weights applied were obtained by w = l/cr 2(F) . The f i n a l d ifference Fourier synthesis contained r e s i d u a l e l e c t r o n density as high as 0.865 eA - 3. This suggested the presence of minor disorder i n the p o s i t i o n s of one of the carbomethoxy groups of each molecule, but sev-e r a l attempts to f i n d the nature of the disorder i . e , to assign the r e s i d u a l peaks on the f i n a l difference Fourier map, proved i n vain. 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A System of Computer Pro-grams f o r the Automatic S o l u t i o n of C r y s t a l S t r u c t u r e s from X-ray D i f f r a c t i o n Data. 59. Busing, W. R.; M a r t i n , K. 0.; Levy, H. A. Report ORNL-TM-306 (ORFFE), Oak Ridge National Laboratory, Tennesse (1964). Johnson, C. K. Report ORNL-3794 (ORTEP), Oak Ridge National Laboratory, Tennesse (1965). -94-APPENDIX T a b l e 1 F i n a l p o s i t i o n a l ( f r a c t i o n a l x 10' 7 H x 103) a n d i s o t r o p i c t h e r m a l p a r a m e t e r s (U x l O 3 A * ) w i t h e s t i m a t e d s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s Atom X y z u A Cl 1 104( 3) -350( 3) -3202( 5) 56 C2 1413( 3) -379( 3) -4563( 5) 68 C3 231 0( 3) -381 ( 4) -4202( 6) 69 C4 2932( 3) -365( 3) -2484{ 5) 58 C4a 2642( 2) -347( 3) - 1 135( 4) 44 C5 28 1 7 ( 3) -2011( 3) 20 1 6 ( 5) 53 C6 2 1 42 < 3) -2759( 3) 2328( 6) 63 C7 1 235 ( 3) -2727( 3) 1 9 1 8 ( 6) 65 C8 988 ( 3) - 1 954 ( 3) 1 2 1 7 ( 5) 56 C8a 1 660 ( 2) - 1 2 11 ( 3) 909( 5) 47 C9 1 528( 3) -305 ( 3) 1 51 ( 5) 50 C9a 1 729 ( 3) -332 ( 3) - 1 496( 5) 47 CIO 3224 ( 2) -367( 3) 84 1 ( 4) 42 C1 0a 2568( 2) - 1 240 ( 3) 1 287 ( 4) 44 Ci 1 2354( 3) 553( 3) 1 486 ( 5) 50 Cl 2 32 1 6 ( 3) 51 0( 3) 1 835 ( 5) 47 Cl 3 42 1 2 ( 3) - 3 9 3 ( 3) 1 2 58 ( 5) 57 C14 2263( 3) 1 376 ( 4 ) 2424 ( 6) 60 C15 1 264 ( 4) 2 1 00 ( 4) 2779( 8) 101 C16 4 1 4 5 ( 3) 1 1 87 ( 3) 31 94 < 5) 52 C17 5506( 4) 2580( 4 ) 3734 ( 7) 94 01 1 34 1 ( 2) 1 258 ( 2) 191 5( 4) 72 02 29 1 2 ( 3) 2026( 3) 3448 ( 4) 81 03 4567( 2) 1 924 ( 2) 2522( 3) 67 04 4498( 2) 1 042 ( 2) 4684( 3) 71 Cl ' 1 1 07 ( 3) 4648( 3) 1 2232( 6) 57 C2' 1 437 ( 3) 4682( 3) 14087( 6) 69 C3' 2346( 3) 4729( 4) 15094( 5) 71 C4' 2970( 3) 4725( 3) 1 4320( 5) 59 C 4 a ' 2668( 2) 4693( 3) 12521( 4) 44 C5' 2887( 3) 2998( 3) 9692( 5) 52 C6' 2234( 3) 2232( 3) 6362( 6) 61 C7' 1325( 3) 2225( 3) 7364( 6) 63 C8' 1056( 3) 3002( 3) 7658( 5) 55 C8a' 1706( 2) 3766( 3) B992( 4) 43 C9' 1 548 ( 2) 4658( 3) 9540( 5) 46 C9a' 1 747 ( 2) 4670( 3) 1 1475( 5) 44 C10* 3255( 2) 4660( 3) 1 1 4 4 6 ( 4) 42 ClOa' 2626( 2) 3766( 3) 1 0020( 4) 43 C11 ' 2352( 2) 5530( 3) 9455( 4) 45 C 1 2 * 3227( 2) 5521 ( 3) 1 0422( 4) ' 44 Cl 3' 4264( 3) 4681 ( 3) 1 2550( 5) 57 c o n t i n u e d * • • - 9 5 -Cl 4' 2217( 3) 6326( 3) 8405 ( 5) 55 Cl 5' 1 1 14( 4) 701 1 ( 4) 6689( 7) 97 C 1 6' 4 1 47( 3) 6212( 3) 1 0478 ( 5) 49 C 1 7' 5472( 3) 7638( 4) 11969( 7) 80 01 ' 1288( 2) 6207( 2) 76 1 0 ( 4) 67 02' 2846( 2) 6975( 2) 8298( 4) 72 03* 4543( 2) 6967( 2) 1 1762( 4) 62 04' 4500( 2) 6 0 6 K 2) 95 1 8 ( 4) 64 H1 47 -34 -346 67 H2 98 -40 -577 82 H3 251 -39 -515 83 H4 357 -37 -223 70 H5 345 -202 230 64 H6 230 -330 283 76 H7 76 -326 212 79 H8 35 -194 95 68 H9 89 -27 -10 62 H1 3a 459 18 94 69 H1 3 b 454 -40 253 69 H1 3 c 415 -98 58 69 Hi 5a 59 201 241 121 Hi 5 b 157 214 407 121 H1 5 c 159 270 244 121 HI 7 a 575 309 312 1 1 3 H ! 7 b 546 287 474 1 1 3 HI 7 c 594 222 415 1 1 3 H1 ' 46 461 1151 68 H2' 101 467 1 465 83 H 3 ' 256 476 1637 86 H4' 361 474 1 504 71 H5' 353 300 1 039 62 H6' 242 170 8 1 3 73 H7' 87 168 645 76 H8' 42 300 693 66 H9* 91 466 8 8 1 59 H13a' 462 527 1343 69 H1 3 b ' 423 41 1 1315 69 H1 3c ' 459 467 1 178 69 H15a' 42 688 613 1 16 H l 5 b ' 144 762 754 1 16 H15c* 136 707 578 1 16 H17a' 571 817 1294 96 H l 7 b ' 593 730 1224 96 H l 7 c ' 541 790 1087 96 -96-T a b l e 2 F i n a l a n i s o t r o p i c t h e r m a l p a r a m e t e r s (U. . x 1 0 3 A 2 ) * a n d t h e i r e s t i m a t e d s t a n d a r d d e v i a t i o n s A t o m V 1 i 2 2 U 3 3 1 2 (7 1 3 u23 CI 4 7 ( 2 ) 61 ( 3 ) 52 ( 2 ) 17( 2) 14( 2) 15( 2) C2 68( 3) 80 ( 3 ) 38 ( 2) 17( 2) 10( 2) 12( 2) C3 71 ( 3) 93( 4 ) 4 7 ( 2) 2 6 ( 3) 30( 2) 19( 2) C4 53( 2) 80 ( 3) 47 ( 2) 2 2 ( 2) 26 ( 2) 15( 2) C 4 a 40 ( 2) 49( 2 ) 41 ( 2) 12( 2) 18( 2) 10( 2) C5 54 ( 2 ) 60( 3) 49 ( 2) 23 ( 2) 23 ( 2) 12( 2) C6 72 ( 3 ) 58( 3 ) 6 4 ( 3) 21 ( 2) 33 ( 2) 18( 2) C7 6 4 ( 3) 59( 3 ) 6 9 ( 3) 6( 2) 35( 2) 15( 2) C8 45( 2) 65( 3 ) 58( 2) 12( 2) 26 ( 2) 12( 2) C8a 42( 2 ) 58( 2 ) 42( 2) 16( 2) 21 ( 2) 12( 2) C9 44( 2) 68( 3 ) 49 ( 2) 27 ( 2) 26( 2) 18( 2) C 9 a 42 ( 2) 53( 2 ) 42( 2) 1 3( 2) 17( 2) 13( 2) C IO 35( 2) 55( 2 ) 38 ( 2) 15( 2) 16( 1 ) 12( 2) CI Oa 43( 2) 53( 2 ) 38 ( 2) 1 7( 2) 19( 2) 10( 2) CI 1 56( 2 ) 58( 2 ) 44 ( 2) 25 ( 2) 24 ( 2) 15( 2) C12 46( 2) 60( 2 ) 39 ( 2) 20 ( 2) 20( 2) 16( 2) CI 3 46 ( 2 ) 78 ( 3 ) 53( 2) 22( 2) 25( 2) 17( 2) C14 68 ( 3) 77 ( 3) 56( 3) 42 ( 3) 33( 2) 31 ( 2) CI 5 1 19( 5) 98 ( 4 ) i 1 8 ( 5) 52 ( 4) 71 ( 4 ) 13( 4) C 1 6 56( 2) 58( 3) 41 ( 2) 21 ( 2) 17( 2) 12( 2) C17 65 ( 3) 92( 4 ) 74 ( 3) - 1 4 ( 3) 1 0( 3) 14( 3) 01 83 ( 2) 84 ( 2 ) 70 ( 2) 44 ( 2) 43( 2) 17( 2) 02 91 ( 2) 81 ( 2 ) 6 3 ( 2) 34( 2) 22( 2) - 6 ( 2) 0 3 60 ( 2) 71 ( 2 ) 48 ( 2) 5( 2) 17( 1 ) 18( 1 ) 04 78 ( 2 ) 79 ( 2 ) 41 ( 2) 24 ( 2) 13( 1 ) 18( 1 ) CI ' 53 ( 2 ) 57 ( 3 ) 7 0 ( 3) 18( 2) 36( 2) 1 1 ( 2) C 2 ' 7 6 ( 3) 72( 3 ) 7 2 ( 3) 12( 3) 54( 3) 4( 2) C 3 ' 77 ( 3) 94( 4 ) 4 5 ( 2) 22 ( 3) 34( 2) 4( 2) C 4 ' 53( 2 ) 83 ( 3 ) 42 ( 2) 24 ( 2) 20 ( 2) 10( 2) C 4 a ' 41 ( 2) 50( 2 ) 43 ( 2) 15( 2 ) 21 ( 2) 8( 2) C 5 ' 53 ( 2 ) 6 0 ( 3) 5 3 ( 2) 25 ( 2) 28 ( 2) 19( 2) C 6 * 69 ( 3 ) 52 ( 3) 66( 3) 16( 2) 37 ( 2) 5( 2) C 7 ' 6 2 ( 3 ) 57( 3) 58( 3) 2( 2) 2 9 ( 2) - 7 ( 2) C 8 ' 42 ( 2 ) 70 ( 3) 44( 2) 1 1 ( 2 ) 18( 2) 9( 2) C 8 a ' 4 0 ( 2 ) 55( 2) 3 6 ( 2) 16( 2 ) 18( 2 ) 10( 2) C 9 ' 33( 2) 62( 3) 43( 2) 20 ( 2 ) 14( 2 ) 14( 2) C9a ' 4 2 ( 2 ) 48 ( 2 ) 4 8 ( 2) 14( 2 ) 24 ( 2) 8( 2 ) C 1 0 ' 38( 2 ) 59( 2) 34( 2) 2 2 ( 2 ) 15( 1 ) 9( 2) C l O a ' 4 0 ( 2 ) 55 ( 2 ) 37( 2) 19( 2 ) 19( 2) 12( 2) ci r 43( 2) 57( 2) 4 2 ( 2 ) 2 2 ( 2 ) 2 2 ( 2 ) 14( 2) C 1 2 ' 41 ( 2 ) 55( 2 ) 3 8 ( 2) 17( 2 ) 20.( 2) 6 ( 2) C 1 3 ' 4 2 ( 2 ) 8 5 ( 3) 4 2 ( 2 ) 25 ( 2 ) 13( 2 ) 12( 2) C 1 4 ' 59 ( 3) 67 ( 3) 47{ 2) 31 ( 2) 24 ( 2 ) 1 1 ( 2 ) C 1 5 ' 94( 4) B8( 4) 8 6 ( 4) 37( 3) 9( 3) 41 ( 3) C16' 4 6 ( 2 ) 58( 2 ) 50 ( 2) 19( 2) 27 ( 2) B( 2) CI 7 ' 51 ( 3) 6 6 ( 4) 8 4 ( 3) - 4 ( 2) 3 2 ( 2) - 1 5 ( 3) - 9 7 -01' 6 1 ( 2 ) 81 ( 0 2 * 74( 2 ) 73 ( 0 3 ' 50( 2) 70 ( 0 4 ' 65( 2 ) 71 ( 2) 67( 2) 35( 2) 88 ( 2) 28 ( 2) 63( 2) 6( 2) 69( 2) 17( 2) 24( 1) 36( 2) 2) 49( 2) 39( 2) 1) 3 1 ( 1 ) - 9 ( 1 ) 2) 45 ( 2) 3 ( 1 ) * T h e a n i s o t r o p i c t h e r m a l p a r a m e t e r s e m p l o y e d i n t h e r e f i n e m e n t a r e V. . i n t h e e x p r e s s i o n : / = / ° e x p ( - 2 i r 2 I I U. h.h.a.*a*) * i j 1J 1 J 1 J -98-T a b l e 3 Bond l e n g t h s (A) w i t h e s t i m a t e d s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s B o n d L e n g t h ( A ) B o n d L e n g t h ( A ) C l -C2 1 . 4 0 7 ( 6 ) C1 * -C2' 1 . 4 1 6 ( 6 ) C l - C 9 a 1 . 3 7 8 ( 5 ) C1 * - C 9 a ' 1 . 3 9 7 ( 5 ) C2 - C 3 1 . 3 6 2 ( 6 ) C2' - C 3 * 1 . 3 5 8 ( 6 ) C3 - C 4 1 . 3 8 6 ( 6 ) C 3 ' - C 4 ' 1 . 3 9 3 ( 5 ) C4 - C 4 a 1.375(5) C 4 ' - C 4 a ' 1 . 3 7 5 ( 5 ) C4a - C 9 a 1.396(5) C 4 a ' - C 9 a ' 1 . 3 9 2 ( 5 ) C4a - C 1 0 1 . 5 5 0 ( 5 ) C4a' - C I O * 1 . 5 4 4 ( 4 ) C5 - C 6 1 . 3 8 9 ( 5 ) C 5 ' - C 6 ' 1 . 3 7 9 ( 5 ) C5 - C l O a 1 . 3 9 4 ( 5 ) C 5 ' - C l O a ' 1 . 387 (5 ) C6 - C 7 1 . 3 8 7 ( 6 ) C 6 ' - C 7 ' 1 . 3 7 5(6) C7 - C 8 1 . 3 8 9 ( 6 ) C 7 ' - C 8 ' 1 .399(6) C8 - C 8 a 1 . 3 8 0 ( 5 ) C 8 ' - C 8 a ' 1 . 378(5) C8a - C 9 1 . 5 2 8 ( 5 ) C 8 a ' - C 9 ' 1 .513(5) C8a - C l Oa 1 . 3 9 2 ( 5 ) C 8 a ' - C l O a ' 1 . 399(5) C9 - C 9 a 1 . 5 2 7 ( 5 ) C 9 ' - C 9 a ' 1.511(5) C9 -C1 1 1 . 5 2 9 ( 5 ) C 9 ' - C l 1 ' 1 . 532 ( 5) CIO - C l O a 1 . 5 3 6 ( 5 ) C I O ' - C l O a ' 1 . 5 2 8(5) C1 0 - C 1 2 1 . 5 3 2 ( 5 ) C 1 0 ' - C 1 2 ' 1 . 5 4 2 ( 5 ) CIO - C 1 3 1 . 5 1 0 ( 5 ) C I O ' - C 1 3 ' 1 . 5 2 0 ( 5 ) C1 1 - C l 2 1.331(5) C l 1 • - C 1 2 ' 1 . 3 3 3 ( 5 ) ci 1 -C1 4 1 . 5 0 9 ( 6 ) C1 1 ' - C l 4 ' 1 . 4 9 5 ( 5 ) C l 2 - C 1 6 1 . 4 8 8 ( 5 ) C l 2 ' -C16' 1 . 4 9 0 ( 5 ) C14 -01 1 . 3 3 1 ( 5 ) C 1 4 ' -01 ' 1 . 3 3 4 ( 5 ) C l 4 - 0 2 1 . 1 7 5 ( 5 ) C 1 4 ' - 0 2 ' 1.185(5) C1 5 -01 1 . 4 8 8 ( 6 ) C1 5 ' -01 ' 1 . 4 6 4 ( 5 ) C l 6 - 0 3 1 . 3 4 0 ( 5 ) C 1 6 ' - 0 3 ' 1 . 3 2 9 ( 4 ) C16 - 0 4 1 . 2 0 1 ( 4 ) C 1 6 ' - 0 4 ' 1 . 2 0 1 ( 4 ) C l 7 - 0 3 1 . 4 4 7 ( 5 ) C 1 7 ' - 0 3 ' 1 . 4 5 1 ( 5 ) - 9 9 -T a b l e 4 Bond a n g l e s ( d e g ) w i t h e s t i m a t e d s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s B o n d s A n g l e ( d e g ) B o n d s A n g l e ( d e g ) C2 -CI -C9a 118.3 (4) C2' -CI ' -C9a' 117.9 4) CI -C2 -C3 120.8 (4) CI ' -C2' -C3' 121.0 4 ) C2 -C3 -C4 120.5 (4) C2' -C3' -C4' 120.6 4) C3 -C4 -C4a 119.7 (4) C3' -C4* -C4a* 119.6 4 ) C4 -C4a -C9a 120.0 (3) C4' -C4a' -C9a' 120.5 3) C4 -C4a -C1 0 126 .8 (3) C 4 ' -C4a' -CIO' 126.3 3) C9a -C4a -CIO 113.3 (3) C9a* -C4a' -C10' 113.2 3) C6 -C5 - C 1 Oa 119.2 4 ) C6* -C5' -Ci Oa 1 1 9 . 7 4 ) C5 -C6 -C7 119.7 (4) C5' -C6' -C7' 120.4 4) C 6 -C7 -C8 121.3 4) C6' -C7' -CB* 120 .6 4 ) C7 -C8 -C8a 118.9 4) C7" -CB' -C8a' 1 1 9 . 2 4) C8 -C8a -C9 126.7 3) C8' -C8a ' -C9' 127 .2 3) C8 -C8a - C 1 Oa 120.5 i 4 ) CB" -CBa' -Ci Oa 120 . 2 4) C9 -C8a -ClOa 1 1 2.8 3) C9' -CBa' - C 1 Oa 1 1 2 . 6 3) C8a -C9 -C9a 104.6 3) C8a' -C9' -C9a" 105.5 3) C8a - C 9 -CI 1 105.6 3) C8a' - C 9 " -C1 1 • 1 06. 1 3 ) C9a -C9 -C i 1 106.3 3) C9a' -C9' -C1 1 ' 106 .2 3) C1 -C9a -C4a 120.7 3) Ci ' -C9a' -C4a' 120.4 3) CI -C9a -C9 126.2 3) C1 ' -C9a' -C9' 126.5 3) C4a -C9a -C9 113.1 3) C4a' -C9a' -C9' 113 .1 3) C4a -CIO -CI Oa 104.6 3) C4a' -CIO' -Ci Oa 105.0 3) C4a -CIO -C12 104.4 3) C4a' -CIO' -C1 2 ' 1 04. 1 3) C4a -CIO -CI 3 114.1 3) C4a' -C10' - C 1 3' 114.5 3) Ci Oa -CIO -CI 2 103.8 3) C1 Oa' -CIO' -C1 2' 104. 1 3) ClOa -C10 -CI 3 114.1 3) C10a' -CIO* -C1 3" 114.3 3) C12 -CIO -CI 3 114.7 3) C12* -CIO' -CI 3' 113.6 3) C5 -CI Oa -C8a 120.4 3) C5' -C10a' -C8a' 120.0 3) C5 -CI Oa -CIO 125.7 3) C5' -ClOa' -CIO' 126.4 3) C8a -C1 Oa -C10 113.9 3) C8a' -ClOa' -CIO' 113.6 3) C9 -C1 1 -C12 113.4 3) C9' - C 1 1 * -C12' 113.2 3) C9 -C1 1 -C14 126.31 3) C9' -C1 1 ' -C14' 125.8 3) C12 -CI 1 -C14 120.2< 4 ) C12' -C1 1 • -C14' 121.0 3) C10 -C12 -C1 1 115.9( 3) CIO' -C12* -C1 1 ' 115.21 3) CIO -C12 -C16 1 18.1 I 3) CIO' -C12' -C16' 118.61 3) C1 1 -C12 -C16 125.81 4 ) C1 1 ' -C12' -C16' 126.01 3) C1 1 -C14 -01 110.01 4 ) C1 1 ' -CI 4 ' -01 ' 110.51 4) CI 1 -C14 -02 124.81 4 ) C1 1 * -C14' - 0 2 ' 124.81 4) 01 -C14 -02 125.21 5) 01 ' -C1 4 * -02' 124.7< 4) C12 -C16 -03 112.21 3) C12* -C16' -03' 112.3< 3) C12 -C16 -04 123. 11 4) C12' -C16* -04' 122.7( 4) 03 -C16 -04 124.61 4 ) 03' -C16' -04' 124.9( 3) C14 -01 -C15 109.31 4 ) Ci 4' -01 ' -C15' 113. 1 ( 4) C16 -03 -C17 115.6( 3) C16' -03' -C17' 115.3< 3) -100-Table 5 Bond lengths i n v o l v i n g hydrogen atoms (A) with estimated standard d e v i a t i o n s in parentheses Bond Length(A) Bond Length(A) C1 -H1 0.970(4) C1 ' -H1 ' 0.970(4) C2 -H2 0.970(4) C2" -H2' 0.970(4) C3 -H3 0.970(4) C3' -H3' 0.970(4) C4 -H4 0.970(4) C4' -H4* 0.970(4) C5 -H5 0.970(4) C5' -H5' 0.970(4) C6 -H6 0.970(4) C6' -H6' 0.970(4) C7 -H7 0.970(4) C7' -H7" 0.970(4) C8 -H8 0.970(4) C8' -H8' 0.970(4) C9 -H9 0.980(3) C9' -H9' 0.980(3) C13 -H1 3a 0.980(4) C1 3' -H13a* 0.980(4) C1 3 -H1 3b 0.980(4) C1 3' -H13b' 0.980(4) C1 3 -HI 3c 0.980(4) C1 3' -HI 3c' 0.980(4) C15 -H1 5a 0.980(6) C15' -H15a' 0.980(5) C15 -HI 5b 0.981(7) C1 5' -H15b* 0.981(6) C15 -HI 5c 0.978(6) C15' -H15c' 0.979(6) C17 -H1 7a 0.981(5) C17* -H!7a' 0.979(5) C17 -H1 7b 0.980(6) C17' -H17b' 0.980(5) C17 -H1 7c 0.979(6) C17' -H17c' 0.980(5) -101-Table6 B o n d a n g l e s i n v o l v i n g h y d r o g e n a t o m s ( d e g ) w i t h e s t i m a t e d s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s B o n d s A n g l e ( d e g ) B o n d s A n g l e ( d e g ) C2 - C l -H1 120 .8 (4) C 2 * - C 1 * -H1 * 1 2 1 . 0 ( 4 ) C 9 a - C 1 -H1 120 .8 (4) C 9 a ' - c r -H1 ' 1 2 1 . 1 ( 4 ) C l - C 2 - H 2 119.6 (5) C l ' - C 2 ' - H 2 ' 1 1 9 . 5 ( 5 ) C3 - C 2 - H 2 119.6 (4) C 3 ' - C 2 ' - H 2 ' 1 1 9 . 5 ( 5 ) C2 - C 3 - H 3 119 .8 (4) C 2 ' - C 3 ' - H 3 ' 1 1 9 . 7 ( 4 ) C4 - C 3 - H 3 119 .8 (4) C 4 ' - C 3 * - H 3 ' 1 1 9 . 7 ( 5 ) C3 - C 4 - H 4 1 2 0 . 1 (4) C 3 ' - C 4 * -H4 ' 1 2 0 . 2 ( 4 ) C4a - C 4 - H 4 120 .1 (4) C 4 a ' - C 4 ' - H 4 ' 1 2 0 . 2 ( 4 ) C6 - C 5 - H 5 1 2 0 . 4 4) C 6 ' - C 5 * - H 5 ' 1 2 0 . 1 ( 4 ) C i 0a - C 5 - H 5 1 2 0 . 4 (4) C1 0 a ' - C 5 ' - H 5 ' 1 2 0 . 2 ( 4 ) C5 - C 6 - H 6 120 .1 (4) C 5 ' - C 6 ' - H 6 ' 1 1 9 . 8 ( 4 ) C7 - C 6 - H 6 1 2 0 . 2 (4) C 7 ' - C 6 * - H 6 ' 1 1 9 . 8 ( 4 ) C6 - C 7 - H 7 1 1 9 . 3 (5) C 6 ' - C 7 ' - H 7 ' 1 1 9 . 7 ( 5 ) C8 - C 7 - H 7 1 1 9 . 3 5) C B " - C 7 ' - H 7 • 1 1 9 . 7 ( 5 ) C7 - C 8 - H 8 120 .6 4) C 7 ' - C B * - H 8 ' 1 2 0 . 4 ( 4 ) C8a - C 8 - H 8 1 2 0 . 5 (4 ) C 8 a ' - C 8 ' - H 8 ' 1 2 0 . 4 ( 4 ) C8a - C 9 - H 9 1 1 3 . 2 k 3 ) C8a * - C 9 ' - H 9 ' 1 1 2 . 8 ( 3 ) C9a - C 9 - H 9 1 1 3 . 2 3) C 9 a ' - C 9 ' - H 9 ' 1 1 2 . 6 ( 3 ) C l 1 - C 9 - H 9 1 1 3 . 2 4 ) C1 1 ' - C 9 ' - H 9 ' 1 1 2 . 8 ( 3 ) CIO - C l 3 -H I 3a 1 0 9 . 5 4 ) C 1 0 ' -C1 3 ' -H1 3a 1 0 9 . 5 ( 4 ) C10 - C 1 3 -H I 3b 1 0 9 . 5 3) C I O ' - C 1 3 ' -H1 3b 1 0 9 . 5 ( 3 ) CIO - C 1 3 - H I 3c 1 0 9 . 5 3) C I O " - C 1 3 ' -H1 3c 1 0 9 . 5 ( 3 ) H1 3a - C l 3 - H i 3b 1 0 9 . 5 (4) H1 3 a ' - C 1 3 * -H1 3b 1 0 9 . 5 ( 3 ) H1 3a - C l 3 - H 1 3 c 1 0 9 . 5 4) H 1 3 a * - C l 3* -H1 3c 1 0 9 . 5 ( 4 ) H1 3b - C 1 3 -H1 3c 1 0 9 . 5 4) H 1 3 b ' - C 1 3 ' -HI 3c 1 0 9 . 5 ( 4 ) 01 - C l 5 - H I 5a 1 0 9 . 4 5) 01 ' - C l 5 ' -H1 5a 1 0 9 . 5 ( 5 ) 01 - C l 5 - H I 5b 1 0 9 . 4 5) 01 ' - C l 5 ' -H1 5b 1 0 9 . 4 ( 4 ) 01 - C l 5 - H I 5c 1 0 9 . 5 [4) 01 ' - C 1 5 ' -H1 5c 1 0 9 . 5 ( 5 ) H1 5a - C 1 5 -H I 5b 1 0 9 . 4 5) HI 5 a * - C 1 5 * -H1 5b 1 0 9 . 4 ( 6 ) H1 5a - C 1 5 -H 1 5 C 109 .6 6) H 1 5 a ' - C 1 5 ' -H1 5c 1 0 9 . 5 ( 5 ) H1 5b - C 1 5 - H I 5c 1 0 9 . 5 6) H 1 5 b ' - C 1 5 ' - H 1 5 c 1 0 9 . 4 ( 5 ) 0 3 - C 1 7 - H l 7 a 1 0 9 . 4 4) 0 3 ' - C 1 7 ' -H1 7a 1 0 9 . 4 ( 4 ) 0 3 - C 1 7 - H 1 7 b 1 0 9 . 5 4) 0 3 * - C 1 7 ' - H l 7 b 1 0 9 . 4 ( 4 ) 0 3 - C 1 7 - H 1 7 c 1 0 9 . 5 5) 0 3 ' - C 1 7 ' -H1 7c 1 0 9 . 4 ( 4 ) H l 7 a - C 1 7 - H l 7 b 1 0 9 . 5 6) H 1 7 a ' - C 1 7 ' - H 1 7 b 1 0 9 . 5 ( 5 ) H l 7 a - C 1 7 - H I 7c 1 0 9 . 5 5) H 1 7 a ' - C 1 7 ' - H 1 7 c 1 0 9 . 6 ( 5 ) H ! 7 b - C 1 7 - H I 7c 109 .6 5) H 1 7 b ' - C 1 7 ' - H 1 7 c 1 0 9 . 5 ( 4 ) -102-T a b l e 7 T o r s i o n a n g l e s ( d e g ) w i t h e s t i m a t e d s t a n d a r d d e v i a t i o n s i n p a r e n t h e s e s A t o m s V a l u e ( d e g ) C9a -C1 -C2 -C3 -0.7 k7 C2 -CI -C9a -C4a -0.2 (6 C2 -C1 -C9a -C9 -179.7 4 CI -C2 -C3 -C4 0.8 8 C2 -C3 -C4 -C4a -0.1 [7 C3 -C4 -C4a -C9a -0.8 (6 C3 -C4 -C4a -C10 177.5 4 C4 -C4a -C9a -C1 1 .0 .6 C4 -C4a -C9a -C9 -179.5 (4 CIO -C4a -C9a -C1 -177.6 (4 C10 -C4a -C9a -C9 1 .9 5 C4 -C4a -C1 0 -ClOa -124.4 (4 C4 -C4a -C 1 0 -Ci 2 126.9 (4 C4 -C4a -C10 -C1 3 1 .0 (6 C9a -C4a -C10 -ClOa 54. 1 (4 C9a -C4a -C 1 0 -CI 2 -54.6 (4 C9a -C4a -C1 0 -Cl 3 179.5 (3 Ci Oa -C5 -C6 -C7 -0.3 [6 C6 -C5 -Cl Oa -C8a 1 .3 (6 C6 -C5 -ClOa -C10 -179 .1 (4 C5 -C6 -C7 -CB -0.7 (7 C6 -C7 -C8 -CBa 0.7 (6 C7 -C8 -C8a -C9 -180.0 (4 C7 -C8 -C8a -Cl Oa 0.3 (6 C8 -C8a -C9 -C9a -122.2 (4 C8 -C8a -C9 -Cl 1 125.8 (4 CI Oa -C8a -C9 -C9a 57.5 (4 CI Oa -CBa -C9 -Cl 1 -54.5 [4 C8 -C8a -C10a -C5 -1 .3 (5 C8 -CBa -C1 Oa -C1 0 179. 1 (3 C9 -C8a -ClOa -C5 178.9 (3 C9 -C8a -C10a -C10 -0.7 4 C8a -C9 -C9a -ci 121.4 (4 C8a -C9 -C9a -C4a -58. 1 4 C1 1 -C9 -C9a - C l -127.2 4 CI 1 -C9 -C9a -C4a 53.3 4 C8a -C9 -C1 1 -C12 55.3 4 CBa -C9 -C1 1 -C14 -122.9i 4 C9a -C9 -C1 1 -C12 -55.5< 4 C9a -C9 -C1 1 -C14 126.41 4 C4a -C10 -C10a -C5 125.51 4 C4a -C10 -ClOa -C8a -54.9( 4 C12 -CIO -C10a -C5 -125.4< 4 C12 -C10 -ClOa -CBa 54.21 4 continued / . . . -103-C13 -CIO -ClOa -C5 0.1 (5) Cl 3 -C10 -ClOa -C8a 179.7 (3) C4a -C10 -C12 -Cl 1 5 4 . 2 [4) C4a -CIO -C12 - C 1 6 -130.8 (3) ClOa -C10 -C12 -Cl 1 -55. 1 (4) ClOa -C10 -C12 - C 1 6 119.9 (3) C13 -CIO -C12 -Cl 1 179.8 (3) Cl 3 -CIO -C12 -C16 -5.2 (4) C9 -C1 1 -C12 -C10 0.5 (4) C9 - c n -C12 -C16 -174.0 (3) C14 -C1 1 -C12 -C10 178.7 (3) C14 -Cl 1 -C12 -C16 4.2 (6) C9 -C1 1 -C14 -01 -0.2 (5) C9 -C1 1 • -C14 -02 179.9 (4) C12 -C11 -C14 -01 -178.2 (3) Cl 2 -C1 1 -C14 -02 1 .9 (6) CIO -C12 -C16 -03 92.4 (4) CIO -C12 -Cl 6 -04 -82.7 (5) Cl 1 -C12 -C16 -03 -93 .2 (5) Cl 1 -C12 -Cl 6 -04 91 .7 (5) C1 1 -C14 -01 -Cl 5 -177 .2 ( 4 ) 02 - C l 4 -01 -Cl 5 2.8 (6) C 1 2 -C16 -03 -Cl 7 -176.1 (4) 04 -C16 -03 -C1 7 -1.1 (6) C 9 a ' -C1 ' - C 2 ' -C3' -0.4 (7) C 2 ' - c r - C 9 a ' - C 4 a ' 2.1 (6) C2' - c i ' - C 9 a ' -C9' -178 . 9 (4) Cl ' - C 2 ' -C3' -C4' -1.3 (8) C2 ' -C3* - C 4 ' - C 4 a ' 1 .3 (7) C 3 ' - C 4 * - C 4 a " -C9a* 0.3 (7) C3' -C4' - C 4 a ' -CIO' -178 . 5 (4) C4' -C4a* -C9a' -C1 ' -2.0 (6) C4' -C4a' -C9a ' -C9' 178.8 (4) C10* -C4a' -C9a' -C1 ' 176.9 (3) CIO' -C4a' -C9a' -C9' -2.2 (4) C4' -C4a* -CIO' -ClOa' 125. 1 (4) C4' -C4a' -C10' -C12' -125.7 (4) C4' -C4a' -CIO' -C13' -1.0 (6) C9a' -C4a' -CIO' -ClOa' -53.7 i4 ) C9a' -C4a' -CIO' -C12* 55.4 4) C9a* -C4a' -CIO' -C13' -179.8 4) ClOa' -C5' -C6' -C7' -0.2 6) C6' -C5' -ClOa' -CBa' -0.6< 5) C6' -C5' -ClOa' -CIO' 179.3) 3) C5' -C6' -C7' -C8' 1 .41 6) C6' -C7' -C8' -CBa' -1 .6( 6) C7' -C8* -C8a' -C9' -178.71 3) C7' -C8' -CBa' -C10a' 0.8! 5) C8' -C8a' -C9' -C9a' 122.51 4) C8' -C8a' -C9' -C11 ' -125.1( 4) ClOa' -CBa* -C9' -C9a' -57.0( 4) ClOa' -C8a' -C9' - C l 1' 55.4< 4) cont i n u e d /... -104-C 8 ' - C B a ' - C l O a ' - C 5 ' 0 . 3 5) C 8 ' - C 8 a ' - C l O a ' - C 1 0 ' - 1 7 9 . 6 3) C 9 ' - C B a ' - C l O a ' - C 5 ' 1 7 9 . 9 3) C 9 ' - C 8 a * - C l O a ' - C I O ' - 0 . 1 4) C 8 a ' - C 9 ' - C 9 a ' - c r - 1 2 0 . 8 4) C B a ' - C 9 ' - C 9 a ' - C 4 a ' 5 8 . 3 4) C l 1 * - C 9 ' - C 9 a ' - C l • 1 2 6 . 9 4) C l 1 • - C 9 ' - C 9 a ' - C 4 a ' - 5 4 . 0 4) C 8 a ' - C 9 ' - C U ' - C 1 2 * - 5 5 . 2 4) C 8 a ' - C 9 ' - C 1 1 ' - C 1 4 ' 1 2 4 . 0 4) C 9 a ' - C 9 ' -C1 1 ' - C 1 2 ' 5 6 . 7 4) C 9 a ' . - C 9 ' - C 1 1 ' - C 1 4 ' - 1 2 4 . 1 4) C 4 a ' - C I O * - C l O a ' - C 5 ' - 1 2 5 . 0 4) C 4 a ' - C 1 0 ' - C l O a ' - C B a ' 5 5 . 0 k 4 ) C 1 2 ' - C I O ' - C l O a 1 - C 5 ' 1 2 5 . 9 (4) C 1 2 ' - C I O ' - C l O a ' - C 8 a ' - 5 4 . 2 (3) C l 3 ' - C I O ' - C l O a ' - C 5 ' 1 . 3 i 5 ) C1 3 * - C I O ' - C l O a * - C 8 a ' - 1 7 8 . 8 (3) C 4 a ' - C I O ' - C 1 2 ' - C 1 1 ' - 5 4 . 1 4) C 4 a ' - C I O ' -C12' - C 1 6 ' 1 3 0 . 5 (3) C l O a ' - C 1 0 * -C12' -C11 ' 5 5 . 7 (4) C l O a ' - C I O ' -C12* - C 1 6 * - 1 1 9 . 7 3) C 1 3 * - C I O ' -C12' - C U ' - 1 7 9 . 3 (3) C 1 3 ' - C I O ' - C 1 2 * - C 1 6 * 5 . 3 (4) C 9 ' - C l 1 ' - C 1 2 ' - C I O ' - 1 . 2 (4) C 9 ' -C1 1 ' - C 1 2 * - C 1 6 ' 1 7 3 . 8 (3) C 1 4 ' - C l 1 ' - C l 2 * - C I O ' 1 7 9 . 5 3) C 1 4 ' -C1 1 ' - C 1 2 ' - C 1 6 ' - 5 . 5 6) C 9 ' - C 1 1 ' - C 1 4 ' - 01 ' 3 . 5 5) C 9 ' -ci r - C 1 4 ' - 0 2 ' - 1 7 6 . 7 4 ) C 1 2 ' - cu * - C 1 4 * - 0 1 ' - 1 7 7 . 3 3) C 1 2 ' - C l 1 ' - C 1 4 ' - 0 2 ' 2 . 4 6) C 1 0 ' - C 1 2 ' - C 1 6 ' - 0 3 ' - 9 2 . 9 4) C 1 0 ' - C 1 2 ' - C 1 6 ' - 0 4 ' 8 3 . 4 5) C1 1 * - C l 2* -C16' - 0 3 ' 9 2 . 2 4) C1 1 ' - C 1 2 ' - C 1 6 ' - 0 4 ' - 91 .4 5) C1 1 ' - C 1 4 ' - 01 * - C 1 5 ' 1 7 4 . 8 4) 0 2 ' - C 1 4 ' - 01 ' - C 1 5 ' - 4 . 9 6) C 1 2 * - C 1 6 ' - 0 3 ' - C 1 7 ' ' 1 7 6 . 1 4) 0 4 " - C 1 6 * - 0 3 ' - C 1 7 ' - 0 . 2 6) C 9 a - C 1 - C 2 - H 2 179 .3< 4) H1 - C 1 - C 2 - C 3 1 7 9 . 3 1 5) H1 - C l - C 2 - H 2 - 0 . 7 ( 7) H1 - C l - C 9 a - C 4 a 1 7 9 . 8 ( 4) H1 - C l - C 9 a - C 9 0 . 3 ( 7 ) C1 - C 2 - C 3 - H 3 - 1 7 9 . 1 ( 5) H2 - C 2 - C 3 - C 4 - 1 7 9 . 2 ( 5) H2 - C 2 - C 3 - H 3 0 . 9 ( 8) C2 - C 3 - C 4 - H 4 1 7 9 . 9 ( 5) H3 - C 3 - C 4 - C 4 a 1 7 9 . 9 ( 4) H3 - C 3 - C 4 - H 4 - 0 . 1 ( 8 ) c o n t i n u e d /. -105-H4 - C 4 - C 4 a - C 9 a 1 7 9 . 2 4 ) H4 - C 4 - C 4 a - C 1 0 - 2 . 5 7) C l O a - C 5 - C 6 -H6 1 7 9 . 7 4) H5 - C 5 - C 6 - C 7 1 7 9 . 7 4) H5 - C 5 - C 6 - H 6 - 0 . 3 7 ) H5 - C 5 - C l O a - C 8 a - 1 7 8 . 7 4) H5 - C 5 - C l O a - C 1 0 0 . 9 6) C 5 -C6 - C 7 - H 7 1 7 9 . 2 4) H6 -C6 - C 7 - C 8 1 7 9 . 3 4) H6 - C 6 - C 7 - H 7 - 0 . 8 7) C6 - C 7 - C 8 - H 8 - 1 7 9 . 3 4) H7 - C 7 - C 8 - C 8 a - 1 7 9 . 2 4) H7 - C 7 -ce - H 8 0 . 8 (7) H8 - C 8 - C 8 a - C 9 0 . 0 7 ) H8 - C 8 - C 8 a - C 1 Oa - 1 7 9 . 7 4) C8 - C 8 a - C 9 - H 9 1 . 4 (6) C l O a - C 8 a - C 9 - H 9 - 1 7 8 . 8 (3) H9 - C 9 - C 9 a -C1 - 2 . 3 (6) H9 - C 9 - C 9 a - C 4 a 1 7 8 . 2 (4 ) H9 - C 9 - C l 1 - C 1 2 1 7 9 . 6 (3) H9 - C 9 - C 1 1 - C 1 4 1 . 5 (5) C 4 a - C 1 0 - C 1 3 -H1 3a 5 9 . 8 (5) C 4 a -C1 0 - C 1 3 -H1 3b 1 7 9 . 8 3) C 4 a - C I O - C 1 3 -H I 3c - 6 0 . 2 (4) C l Oa - C 1 0 - C 1 3 -H1 3a - 1 8 0 . 0 (3) C i Oa - C 1 0 -C1 3 -H1 3b - 6 0 . 0 (5) C l Oa - C 1 0 - C l 3 - H i 3c 6 0 . 0 (4 ) C12 - C 1 0 - C l 3 -H1 3a - 6 0 . 5 (4) C12 - C 1 0 - C 1 3 -H I 3b 5 9 . 5 (5) C12 - C 1 0 - C l 3 -H1 3c 1 7 9 . 5 (3 ) HI 5a - C 1 5 -01 - C 1 4 - 1 7 9 . 9 (4) HI 5b - C 1 5 -01 - C 1 4 - 6 0 . 1 (6) H1 5c - C 1 5 -01 - C 1 4 6 0 . 0 (6) H l 7 a - C l 7 - 0 3 - C 1 6 - 1 8 0 . 0 (5) H ! 7 b - C 1 7 - 0 3 -C16 - 6 0 . 1 (6) HI 7c - C 1 7 - 0 3 - C 1 6 6 0 . 0 (6) C 9 a ' - C 1 ' - C 2 ' - H 2 ' 1 7 9 . 6 . 4 ) H1 • - C 1 ' - C 2 ' - C 3 ' 1 7 9 . 7 (5) H1 ' - C l ' - C 2 ' - H 2 ' - 0 . 3 7) HI * - C l ' - C 9 a ' - C 4 a ' - 1 7 8 . 1 (4) H I ' - C 1 ' - C 9 a ' - C g - 1.0 7) c r -C2' - C 3 ' - H 3 ' 1 7 8 . 8 4) H 2 ' -C2' - C 3 ' -C4' 1 7 8 . 7 5 ) H 2 ' -C2' - C 3 ' - H 3 ' -1.2 8) C2' - C 3 ' -C4' - H 4 ' - 1 7 8 . 8 5) H 3 ' - C 3 ' -C4* - C 4 a ' - 1 7 8 . 8 4) H 3 ' - C 3 * - C 4 ' - H 4 ' 1 .1 r 8 ) H 4 ' -C4' - C 4 a ' - C 9 a ' - 1 7 9 . 6 4) H 4 ' -C4' - C 4 a ' - C I O ' 1.6 7 ) C l O a * - C 5 ' - C 6 ' - H 6 ' 1 7 9 . 8 3) H 5 ' - C 5 ' - C 6 ' -C7' 1 7 9 . 8 4 ) H 5 ' -C5' - C 6 ' - H 6 ' - 0 . 2 6) continued /... -106-H 5 ' - C 5 ' - C 1 0 a ' - C 8 a ' 1 7 9 . 4 ( 3 ) H 5 ' - C 5 ' - C l O a ' - C I O ' - 0 . 7(6) C 5 * -C6' - C 7 ' - H 7 * -1 7 8 . 6 (4) H6' - C 6 ' - C 7 ' - C 8 ' -1 7 8 . 6 (4) H6' - C 6 ' - C 7 ' - H 7 ' 1 . 4 ( 7 ) C6' - C 7 ' - C 8 ' - H 8 ' 1 7 8 . 3 ( 4 ) H 7 ' - C 7 * - C B ' - C 8 a ' 1 7 8 . 3 ( 4 ) H 7 ' - C 7 ' - C 8 ' - H 8 ' -1 . 7(6) H 8 ' - C 8 ' - C 8 a ' - C 9 ' 1 . 3(6) H8* - C 8 ' - C 8 a ' - C l O a ' -1 7 9 . 2 ( 3 ) C 8 ' - C 8 a ' - C 9 ' - H 9 ' -1 . 0 ( 5 ) C l O a * - C 8 a ' - C 9 ' - H 9 ' 1 7 9 . 4 ( 3 ) H 9 ' - C 9 * - C 9 a ' - C l • 2 . 8 ( 6 ) H9* - C 9 ' - C 9 a * - C 4 a ' -1 7 8 . 1(3) H 9 ' - C 9 ' -cn ' - C 1 2 ' -1 7 9 . 2 ( 3 ) H 9 ' - C 9 ' -C1 1 ' - C 1 4 ' 0 . 0 ( 5 ) C 4 a * - C I O * - C 1 3 ' - H 1 3 a ' - 5 8 . 9 ( 5 ) C 4 a ' - C I O ' - C 1 3 ' - H 1 3 b ' 61 . 1(5) C 4 a ' - C I O ' - C 1 3 ' - H 1 3 c ' -1 7 8 . 9 ( 3 ) C l O a ' - C 1 0 ' - C 1 3 ' - H l 3 a ' -1 8 0 . 0 ( 3 ) C l O a ' - C I O ' -C1 3 ' - H 1 3 b ' - 6 0 . 0 ( 4 ) C l O a ' -C1 0 ' - C 1 3 ' - H 1 3 C ' 6 0 . 0 ( 5 ) C 1 2 ' - C 1 0 ' - C l 3 ' - H 1 3 a ' 6 0 . 6 (4) C 1 2 ' -C1 0 ' -C1 3 ' - H 1 3 b ' -1 7 9 . 3 ( 3 ) C 1 2 ' - C 1 0 ' -C1 3 ' - H 1 3 c ' - 5 9 . 4 ( 5 ) H 1 5 a ' - C 1 5 ' -01 ' - C 1 4 ' -1 7 9 . 9 ( 5 ) H1 5 b ' - C 1 5 ' -01 ' - C 1 4 ' - 6 0 . 1(6) H 1 5 c ' - C 1 5 ' - 01 ' - C 1 4 ' 5 9 . 9(6) H i 7 a ' - C 1 7 ' - 0 3 ' -C16' -1 8 0 . 0 ( 4 ) H 1 7 b ' - C 1 7 ' - 0 3 ' - C 1 6 ' - 6 0 . 0 ( 5 ) H 1 7 c ' - C 1 7 ' - 0 3 ' - C 1 6' 6 0 . 0 ( 5 ) 

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