Columnar phases from semi-discoid molecules. Phase induction via hydrogen bonding and charge transfer interactions

Abstract

To investigate the non-linear optical properties of nitrophenylhydrazones, a series of 4-nitro- and 2,4-dinitrophenylhydrazones of substituted aromatic aldehydes were synthesized. It was found that many of the dinitrophenythydrazone derivatives are liquid-crystalline and X-ray investigations show that the mesophase corresponds to a hexagonal columnar structure. To explain this unusual behaviour it is necessary to assume that a mesogenic structure is formed by intramolecular hydrogen bonding of the dinitrophenylhydrazones. Charge transfer induced antiparallel alignment of these moleculer dipoles leads to discoid structures, forming the columnar phases.