J. Phys. Chem. 1981, 85, 2594-2597
2594 AI
AI
P
6
I
AI-0-Si-0-AI
I I AI 0
I
or
AI-0-SI-0-AI
I
dI
SI
regular coordination shells around the Si. In cancrinite, for example, one form has only 4:O ordering, the other 3:l. This, in effect, means that there are two distinct minerals corresDondina to the idealized aluminosilicate framework (A16Sii024)6-.In all zeolites with Si:Al = 1, a 3:l ordering scheme (which, so far, has been identified in Linde A, Losod, sodalite, and cancrinite) inevitably means that A1-0-A1 linkages are a prominent part of the framework structure. Although at first sight it may appear that such linkages cause an increase in lattice energy compared with a structure composed of alternating (A1-O-Si)2, we know
from detailed corn put at ion^^^"^ that, depending upon a variety of factors concerning the nature and location of exchangeable cation, such structures, possessing A1-0-A1 bridges, may be more stable than those composed entirely of A1-0-Si.
Acknowledgment. We thank BP and the Universities of Cambridge and Guelph for supporting this work. We are grateful to Professor R. M. Barrer, F.R.S., and Professor w. M. Meier for a loan of samples, and to Professor E. Lippmaa of the Estonian Academy of Sciences and Dr. G. Engelhardt of the Academy of Sciences of the DDR and advance information and for drawing our attention to bicchulite. (32)R. M. Barrer and J. Klinowski, Philos. Trans. R. SOC. London, Ser. A , 285,637-80 (1977). (33)C. R. A. Catlow, J. M. Thomas, J. Klinowski, et al., manuscript in preparation. (34)S. Ramdas, J. M. Thomas, J. Klinowski, C. A. Fyfe, and J. S. Hartman, Nature (London),in press. (35)K. Sahl, Z.Kristallogr., 152,13-21 (1980).
Crystal Engineering of Photodlmerizabie Cyclopentanones. Comparison of Chioro and Methyl Substitution as Solid-State Steering Groups Willlam Jones, Subramanlam Ramdas, Charis R. Theocharls, John M. Thomas,’ and Noel W. Thomas Department of Physical Chemistry, University of Cambridge, Cambridge CB2 lEP, United Kingdom (Received: Aprll24, 198 1; In Fh8l Form: June 30, 198 1)
The interchangability of chloro and methyl groups, insofar as solid-state structure and photoreactivity are concerned, is examined in a family of three pairs of closely related molecules derived from the same parent, 2-benzyl-5-benzylidenecyclopentanone.The expected behavior of two pairs (supporting the notion of interchangability) and the unexpected behavior of another me rationalized conformationallyand crystallographically. It has been previously demon~tratedl-~ that modifications may be made to molecular structure, shape, and stereochemistry in such a way as to design and engineer organic solids which display a desired photoreactivity which, in turn, enable crystalline products to be formed isomorphously and topochemically within selected monomer matrices. One of the substitutions frequently employed in this general, crystal engineering6-8approach is the replacement of methyl by chloro groups, especially as substituted in alkyl or aryl moieties. Kitaigor~dskii~ and others1&14have, using the principle of close packing, drawn attention to the merit of interchanging substituents for
certain tactical purposes, in such a way that each group occupies approximately the same volume. Since packing considerations hold sway in topochemistry, much useful progress has been made in evolving structure-reactivity patterns, or in enhancing or suppressing photoreactivity, using simple expedients such as the interchange of chloro and methyl groups. In this communication we describe two novel examples of the usefulness of the interchangabilityof these particular groups, and one example where other factors besides
~~
(1)F. L. Hirshfeld and G. M. J. Schmidt, J. Polym. Sci., A2, 2181 (1964). (2)H. Nakanishi, W.Jones, J. M. Thomas, M. Hasegawa, and W. L. Rees, h o c . R. SOC.London, Ser. A , 369, 307 (1980). (3)W. Jones, H. Nakanishi, C. R. Theocharis, and J. M. Thomas, J. Chem. SOC.,Chem. Commun., 610 (1980). (4)R. Popovitz-Biro, H.C. Chang, C. P. Tang, N. Shochet, M. Lahav, and L. Leiserowitz, Pure Appl. Chem., in press. (6)B. S. Green, M. Lahav, and D. Rabinovich, Acc. Chem. Res., 12, 191 (1979). (6)G. M. J. Schmidt, Pure Appl. Chem., 27,647 (1971). (7)M.D.Cohen and B. S. Green, Chem. Brit.,9,490(1973);I. C. Paul and D.Y. Curtin, Acc. Chem. Res., 7,223 (1973). (8) J. M. Thomas, Philos. Trans. R. SOC. London, 277,251(1974);Pure Appl. Chem., 51, 1065 (1979);Nature (London),289,633 (1981). (9)A. I. Kitaigorodskii in “Molecular Crystals and Molecules”, Academic Press, LoGdon, 1973. (10) M. D. Cohen and G. M. J. Schmidt, J. Chem. SOC.,1996 (1964). (11)G. M. J. Schmidt in “Reactivity of the Photoexicted Organic Molecule”, Interscience, New York, 1967. 0022-3654/81/2085-2594$01.25/0
X
(-) d e n o t e s light stability (+ ) d e n o t e s photodimerizability
1(Bp-ClBCP), Y = H , X = p - C l ( - ) 2 (Bp-MeBCP), Y = H , X = p - M e (-) 3 (p-ClBBCP), Y = p-C1, X = H (+ ) 4 (p-MeBBCP), Y = p-CH,, X = H (+ ) 5 (p-ClBpBrBCP, Y = p-C1, X = p-Br (-) 6 (p-MeBp-BrBCP), Y = p-Me, X = p-Br (+ ) (12)M. D.Cohen in “Solid State Photochemistry”, D. Ginsburg, Ed., Weinheim, New York, 1976. (13)J. J. Mayerle and T. C. Clarke, Acta Crystallogr.,Sect. B, 34,143 (1 ~ 978). - -_,. .
(14)J. M. Thomas, S.E. Morsi, and J. P. Desvergne, Adu. Phys. Org. Chem., 15,63 (1977).
0 1981 American Chemical Society
The Journal of Physlcal Chemistry, Vol. 85, No. 18, 1981
Letters
2595
TABLE I: Crystallographic Data and Photoreactivities of Members of the Benzylbenzylidenecyclopentanone Family (See T e x t ) whether photodimerizable ref 1 (Bp-ClBCP) 2 (Bp-MeBCP) 3 (p-ClBBCP) 4 fp-MeBBCP) 5 (p-ClBpBrBCP) 6 @-MeBp-BrBCP)
H H p-c1 p-CH, p-C1 p-CH,
p-c1 p-CH, H H p-Br p-Br
30.97 31.04 17.18 17.34 17.53 18.88
8.50 8.45 10.59 (76.33) 10.68 (102.55) 7.91 (91.19) 11.21 (94.46)
11.57 11.68 8.80 8.74 11.89 8.29
Pbca Pbca P2,lc P2,lc P2,lc P2,lc
no no Yes yes no Yes
3, 3, 3, 3, 3, 3,
19 19 20 19 21 21
\
4
L.03 A L
r
PJ%U**L
( -
?%b-'
k
d
W-LM c,3
r;i
1' (a)
(b)
Flgure 1. (a) The mode of packlng in crystals of 3 (and also 4 see text) is such that an adjacent, centrosymmetrically related pair of monomer molecules have a C6-C,3r separatlon distance of only 4.03 A. 3 and 4 are photodlmerizable. (b) In crystals of 1 (and 2 see text) the Cs-CI3, distance between neighboring molecules is 5.03 A, and these crystals are light stable.
(b) Figure 2. Molecular conformations (viewed along the C2-Cs bond) taken up in the crystalline state of 5 (a) and 6 (b). Molecules in 5 possess an angle of 65' between the bonds C1-Cp and CB-C,, whereas these bonds in 6 are parallel. The second of these two conformations is closely followed in most of the members of this family of compounds. The two planes characterized by the benzyl and benzylidene moieties determine the dihedral angle of the molecule (97 and 68', respectively, in 5 and 6).
volume dominate. All three pairs involve cyclopentanone derivatives3J5J6possessing the skeletal framework of 2benzyl-5-benzylidenecyclopentanone(BBCP). In accordance with expectation, compounds 1 and 2 are isomorphous (see Table I) and both are light stable, whereas componds 3 and 4, which are also an isomorphous pair, are photoreactive. The photoreactivity of 3 and 4 arises because (see Figure la) the separation distances of the collinear olefinic bonds of adjacent, centrosymmetrically related molecules (incipient dimer) are sufficiently (15) H. Nakanishi, W. Jones, J. M. Thomas, M. B. Hursthouse, and M. Motevalli, J. Chem. Soc., Chem. Commun., 611 (1980). (16) H. Nakanishi, W. Jones, J. M. Thomas, M. B. Hursthouse, and M. Motevalli, submitted for publication.
close (e.g., the C5--CI3
