Influence of metal–metal interaction on magnetic and redox properties in different series of heterodinuclear copper(II), nickel(II), and zinc(II) complexes

Abstract

Different series of heterodinuclear complexes, viz.,|CuNiL](ClO4)2•nH2O,[CuZnL](ClO4)2•nH2O,[NiCuL](ClO4)2•nH2O, and [NiZnL](ClO4)2•nH2O complexes where L is a dinucleating Schiff base ligand derived from the condensation of 1 mole of 2-hydroxy-5-methylbenzene-1,3-dicarbaldehyde, 1 mole of 1,3-diaminopropane, and 2 moles of ortho- or para-substituted aniline, have been synthesized and investigated. The μeff values of the CuNiL and NiCuL series of complexes suggest presence of weak antiferromagnetic coupling in them. In MeCN and DMF the CuNiL and NiCuL series of complexes exhibit two reversible one-electron redox couples at two different potentials. The large separation between the two redox couples is attributed to the antiferromagnetic interaction between the metal centres in the complexes. In the NiCuL series of complexes, the observed shift of 100–150 mV in E1 to more negative values in complexes with potential donor groups such as OMe, OEt, SMe, etc. in the ortho position of the phenyl group of L is explained on the basis of weak bonding interactions of these groups with the copper centre. The CuNiL series of complexes do not exhibit such shift in E1 values since there is no significant change in the square planar geometry of the copper centre. The CuZnL and NiZnL series of complexes exhibit only single one-electron redox couple as could be anticipated.