Synthesis and Liquid Crystalline Properties of some Esters of 4-Ferrocenyl-4’-hydroxyazobenzene

Abstract

The paper describes synthesis and mesogenic behavior of a new class of ferrocenomesogens obtained by esterification of 4-ferrocenyl-4’-hydroxyazobenzene with some 4-n-alkyloxybenzoic acids / 4-n-alkanoyloxy or 4-n-alkenoyloxybenzoic acids in the presence of N,N’-dicyclohexylcarbodiimide and 4-dimethylaminopyridine. Based on differential scanning calorimetry and polarized optical microscopy investigations, it was established that 12 from the 15 synthesized compounds presented liquid crystalline properties, mainly monotropic nematic. All the investigated compounds were thermally stable in the existence range of the mesophases. Molecular modeling studies have been performed in order to establish correlations between structure and liquid crystalline properties. Parameters as lengths, diameters, dipole moments and molecular asymmetry coefficients and geometries of minimum energy have been obtained. A model of a cell of minimum energy for systems containing eight molecules of type 4-((4-ferrocenyl-phenylazo)phenyl) 4-alkyloxybenzoate has been proposed.