Crystal structure of mesogenic 3-(benzyloxycarbonyl)-4-(4- n-octyloxybenzoyloxy)benzoic acid

Abstract

The crystal and molecular structure of the title compound 1a has been determined by X-ray analysis. 1a crystallizes in space group PI with two molecules in a unit cell of dimensions: a = 5.516(1), b = 13.186(4), c = 18.364(5) A ̊ , α = 95.82(3), β = 92.14(2), γ = 100.17(2)°. The structure was solved by direct methods and refined on F 2 to R values of wR 2 = 0.100 and R 1 = 0.070, respectively, for 1739 observed unique reflections. The molecules of 1a are associated to dimers by hydrogen bonds between their carboxyl groups. The mesogenic core of the molecules shows a markedly stretched shape but surprisingly the bulky lateral substitutent is oriented nearly perpendicular to it. The crystal structure is characterized by a perfect parallel alignment and an interlocked packing of the dimers. 1a exhibits a considerably different molecular and crystal structure from two isostructural compounds that differ only from 1a by a nitro or cyano substituent, respectively, in the p-position of the benzene ring of the lateral substituent.