Thermotropic Mesomorphism in Salen-like Zinc Complexes

Abstract

The reaction between a series of non mesogenic tetradentate salen-like Schiff bases and Zn(II) acetate gives rise to the formation of liquid cristalline complexes showing nematic and smectic phases stable over a quite large temperature range. A dimeric structural arrangement could favour the appearance of such type of mesophase in the case of 1,3-diaminopropane and 1,3-diamino-2,2-dimethylpropane bridges containing ligands while for the salen derivatives a monomeric solvent-induced pentacoordinated arrengement observed in solution and in the crystalline molecular structure, probably prevent the liquid crystalline behaviour.

Synthesis and Liquid-Crystalline Properties of N,N′-di-(5-(4-Alkoxyphenyl)azo)-Salicylidene-1,2-Phenylene Diiminato Nickel(II) Complexes

“…This complex exhibits low transition temperatures in comparison with the title complexes of this work and undergo decomposition near the transition to the isotropic liquid. Finally, Aiello et al [30] reported a new type of zinc(II) complexes derived from tetradentate salen-like Schiff-base ligands containing …”

“…These complexes show nematic and smectic C(S m C) mesophases [30]. However, the complexes described in this work are more thermally stable than those based on ethylene and trimethylene bridges.…”