Noncovalent Polymer-like Structures of 1,1'-Bicyclohexylidene-4,4'-dione Dioxime and 1,1'-Bicyclohexyl-4,4'-dione Dioxime. Chiral Recognition in the Solid State
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- 作者：Albert W. Marsman ; Erik D. Leussink ; Jan W. Zwikker ; Leonardus W. Jenneskens ; Wilbert J. J. Smeets ; Nora Veldman ; and Anthony L. Spek
- 刊名：Chemistry of Materials
- 出版年：1999
- 出版时间：June 1999
- 年：1999
- 卷：11
- 期：6
- 页码：1484 - 1491
- 全文大小：156K
- 年卷期：v.11,no.6(June 1999)
- ISSN：1520-5002
文摘
As a consequence of the high activation barrier for oxime nitrogen inversion, the dioximes1,1'-bicyclohexylidene-4,4'-dione dioxime (1) and 1,1'-bicyclohexyl-4,4'-dione dioxime (2) aswell as their related monooximes 1,1'-bicyclohexylidene-4-one oxime (3) and 1,1'-bicyclohexyl-4-one oxime (4) consist of a mixture of stereoisomers. For 1, the configurational stereoisomers1-E and 1-Z were identified in solution in a ratio 1:1 (13C NMR). Moreover, in the solidstate, 1-Z as well as 3 also consist of conformational enantiomers, viz. 1-Z(RR)/1-Z(SS) and3-R/3-S, respectively, which rapidly interconvert in solution due to ring inversions of thecyclohexyl moieties. Whereas dioxime 2 consists of an enantiomer pair (2-RR/2-SS) and ameso form (2-RS/2-SR) in a ratio 1:1:2, for monooxime 4 an enantiomer pair (4-R/4-S) in aratio 1:1 is found (chiral HPLC). Upon recrystallization of crude 1-4 no segregation ofstereoisomers occurs [1H and 13C NMR, FT-IR, (chiral) HPLC, and WAXD]. Both dioximes1 and 2 crystallize in the achiral P21/c space group and possess nearly identical structuresbuild up from stacked layers consisting of parallel oriented noncovalent polymer-like chainsformed via intermolecular oxime dimer formation by (self) complementary hydrogen bonding[
(6) motif in graph-set notation]. In the unit cell both molecules possess Ci symmetry. Inaddition, Ci symmetry is found in the six-membered rings resulting from hydrogen bondingof two oxime groups. Similar centrosymmetric oxime dimerization is also observed for 3and 4 in the solid state. The Ci symmetry and the presence of multiple stereoisomers can bereconciled if chiral recognition is operational in the solid state, i.e. intermolecular dimerichydrogen bonding occurs only between oxime groups of units possessing opposite configurations. This poses restrictions on the stereoisomer distribution within the noncovalent polymer-like chains, viz. it dictates their linear rodlike topology. The oxime disorder observed in allcrystal structures is attributed to random stacking of differently oriented noncovalentpolymer-like chains (1 and 2) or dimers (3 and 4).
(6) motif in graph-set notation]. In the unit cell both molecules possess Ci symmetry. Inaddition, Ci symmetry is found in the six-membered rings resulting from hydrogen bondingof two oxime groups. Similar centrosymmetric oxime dimerization is also observed for 3and 4 in the solid state. The Ci symmetry and the presence of multiple stereoisomers can bereconciled if chiral recognition is operational in the solid state, i.e. intermolecular dimerichydrogen bonding occurs only between oxime groups of units possessing opposite configurations. This poses restrictions on the stereoisomer distribution within the noncovalent polymer-like chains, viz. it dictates their linear rodlike topology. The oxime disorder observed in allcrystal structures is attributed to random stacking of differently oriented noncovalentpolymer-like chains (1 and 2) or dimers (3 and 4).