The x-ray crystal structures and computational analysis of NH...π hydrogen bonded banana-shaped carbazole derivatives and thermal analysis of higher mesogenic homologues

The synthesis of a series of banana-shaped mesogenic structures has been carried out, in which the bend unit is formed by the 3,6-substitution of carbazole by 4-alkoxyphenyl moieties. The crystal structures of the methoxy and propyloxy derivatives are reported with an analysis of the N-H...pi interactions that are observed in the crystalline state. This analysis was aided by semi-empirical molecular orbital calculations. Additionally, the thermal analysis of the complete series has been carried out in order to investigate the phase properties of these materials. The 4-nonyloxyphenyl derivative displays two melting points by DSC and normal light microscopy, but yields non-birefringent liquids. The incorporation of photorefractive molecular units, such as carbazole. into anisotropic materials may offer many advantages over conventional electrical poling of photorefractive polymers.