Crystal and molecular structure of mesogenic 4-ethoxy-3′-(4-ethoxy-phenyliminomethyl)-4′-(4-methoxy-benzoyloxy)azobenzene

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Abstract
4-Ethoxy-3′-(4-ethoxy-phenylimino-methyl)-4′-(4-methoxy-benzoyloxy)-azobenzene (EEMA) exhibits liquid crystalline behaviour despite the strong deviation of the molecule from both rod-like and disc-like shape. In order to obtain further information about EEMA the compound was resynthesized and a single-crystal X-ray analysis was performed. EEMA crystallizes in the triclinic space group P1 with two molecules per unit cell. The structure was solved by direct methods and refined to R = 0.058 (Rw = 0.055) for 2473 observed reflections. The EEMA molecule has a bifurcated shape. The phenyliminomethyl branch is bent markedly from the nearly linear three-ring basic fragment but is almost coplanar with the azobenzene moiety. The molecular conformation is apparently affected by an intramolecular interaction of the carboxylic and azomethine group (close C … N contact distance of 2.783(5) Å). The molecular packing in the crystal can be described in terms of a sheet structure with interdigitating comb-like rows of molecules within the sheets.