Liquid crystalline properties of o-hydroxy substituted Schiff's bases and their copper(II) and palladium(II) complexes

Abstract

The synthesis and liquid crystalline properties of thirty nine compounds are reported. These include a homologous series of N-(2-hydroxy-4-n-alkoxybenzylidene)-4''-n-dodecylphenylanilines and their corresponding copper(II) and palladium(II) complexes. Differential scanning calorimetry and optical microscopy were used to characterise the mesophases. The Schiff's bases exhibit polymesomorphism while their metal chelates basically show smectic A (SA) and smectic C (Sc) phases except for a few derivatives. The transition temperatures of the metal chelates are considerably higher than the ligands from which they are derived. A comparison of the mesomorphic properties of the copper chelates with those of bis[4-(4-alkoxybcnzoyloxy)-N-(4-ethoxyphenyl)salicylaldiminato]copper(II) complexes have also been made. Though the melting points of copper(II) and their corresponding palladium(II) chelates of many homologues are comparable, the clearing points of the latter are consistently higher.