Mesogenic Properties of Binucleating Schiff-Base Ligands with Long Side Chains and Their Binuclear Cu(II) and Ni(II) Complexes

Abstract

ABSTRACT Liquid-crystalline binucleating ligands, 1,4-[bis(2-hydroxy-4-(n-alkoxy)benzaldimino]benzene, and their binuclear nickel and copper complexes have been synthesized, with the aim to study the effect of the long alkoxy chain substituents on the mesogenic properties of the ligand and on the extent of electronic interaction between the two paramagnetic metal centers for binuclear Cu(II) complexes. The ligand and the complexes have been characterized by elemental analyses, IR, 1H NMR, and FAB mass and electronic spectral studies. Magnetic moment studies of the Cu (II) complexes show that there is antiferromagnetic spin-exchange interaction between the two Cu (II) centers through the phenyl bridge. The variable temperature magnetic studies show that the extent of spin-exchange interaction decreases with the increase in the length of the alkoxy side chain. The ligands 1,4-bis-(2-hydroxy-4-(n-alkoxy)benzaldimino)benzene exhibit liquid-crystalline properties with the smectic C phase. The mesogenic property of the ligand disappears on complex formation.