The Crystal and Molecular Structures of Four Homologous, Mesogenic trans,trans-4,4′-dialkyl-(1 α,1 ′-bicyclohexyl)-4ß-carbonitril (CCN's)

Abstract

The crystal and molecular structures of four homologous (R′(CN)-C₆H₉-C₆H₁₀-R, CCN's) were determined using single crystal x-ray diffraction data. In all four structures the cyano groups occupy axial positions whereas the alkyl groups occupy equatorial ones. The cyclohexane rings are approximately perpendicular to each other in CCN33 (R˭R′˭C ₃ H₇), in CCN35 (R˭C ₃ H₇, R′˭C ₅ H₁₁) and in CCN38 (R˭C ₃ H₇, R′˭C ₈ H₁₇) leading to a room filling of the free space produced by the cyano groups. More than that, the hydrogen-hydrogen contacts between the cyclohexane rings are minimal in such an arrangement. However, in CCN46 (R˭C ₄ H₉, R′˭C ₆ H₁₃) the molecules contain nearly coplanar bicyclohexyl moieties. These and some other structural features are discussed with regard to the question of the extent to which the crystalline state can be interpreted as a precursor of liquid crystalline states.

Key Words:

• crystalline state
• molecular conformation
• CCH's
• CCN's