Crystal and mesophase structure of a bicyclohexyl cyano mesogen.
Acta Crystallogr C Struct Chem
; 78(Pt 11): 647-652, 2022 Nov 01.
Article
em En
| MEDLINE
| ID: mdl-36331889
The phase behaviour of 4-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]benzonitrile, C22H31N, 1, has been examined. This compound has two different solid phases, denoted I and II, and exhibits thermotropic liquid-crystalline behaviour, with a remarkable interval of stability of the mesophase between the lower melting solid phase (75â
°C) and the isotropization temperature (247â
°C). The crystal and molecular structures of solid phase I have been determined at 173â
K. The cyclohexyl rings both adopt the chair conformation and are equatorially substituted. The packing of 1 in the crystalline state is driven by the antiparallel arrangement of cyano dipoles with the formation of close contacts involving the strong cyano acceptor and weak aromatic C-H or aliphatic C-H donors. The crystal packing is discussed and compared with X-ray diffraction data in the liquid-crystalline state. The combination of thermal analysis, optical polarizing microscopy and X-ray diffraction analysis suggests that the mesophase is a partially ordered smectic phase. The lamellar structure of the mesophase is retained in crystalline solid phase II obtained by cooling the liquid-crystalline phase.
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MEDLINE
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2022
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Article