Crystal structure analysis of some mesogenic cyanoazines

The crystal structure analysis of the following three mesogenic cyanoazines is reported: 4-methoxybenzaldehyde-(4-cyanobenzylidene)hydrazone (E, E) (azine 1), 4-methoxyacetophenone- (4-cyanobenzylidene)hydrazone (E, E) (azine 2), 4-methoxybenzaldehyde-[4-cyanophenyl)-ethylidene]hydrazone (E, E) (azine 3). These azines are simple models of monomeric precursors for the synthesis of comb-like polymers with potential nonlinear optical properties of the second order. The crystal structures have been determined at room temperature by direct methods and refined by full matrix least squares method. Some differences in the solid state conformation of the azines are found as a result of the introduction of a methyl group onto the azine system. The relation between molecular conformation and mesogenic behavior of the three azines is also discussed.