Conformational Behaviour of the Nematogenic Compound 4-Cyanophenyl-trans-4-[(trans-4-n-butylcyclohexyl)methyl]-cyclohexanoate—Crystal Structure and Theoretical Conformational Analysis

Abstract

The title compound, with the formula C₄H₉—C₆H₁₀—CH₂—C₆H₁₀—COO—C₆H₄CN (CBMC), crystallizes in the monoclinic space group P2₁/n with a = 6.4075(7) Å, b = 18.345(2) Å c = 19.423(2) Å, β = 98.614(9) Å and four molecules per unit cell. The structure was solved by direct methods and refined to R = 0.052. The CBMC molecules adopt an elongated banana-shaped form enabling the formation of a monotropic nematic phase 2 degrees below the melting point.

The X-ray experiments were complemented by a conformational analysis of the phenyl-4-cyclohexylmethyl-cyclohexanoate moiety using the EPEN/2 method. The Molecular structure existing in the crystal (and probably also in the mesophase) agrees very well with the most stable conformation indicated by calculation. In the conformational analysis the molecular 1ength:width ratio was also taken into consideration.

The synthesis of CBMC, which represents a new type of mesogen, is described.