Synthesis, spectroscopic and redox behaviour of copper(II), nickel(II) and cobalt(II) complexes of some macrocyclic multidentates

Copper(II) complexes of neutral tetradentate diamines and a series of copper(II), nickel(II) and cobalt(II) complexes of a new class of dibasic hexadentate Schiff bases, derived from the above diamines and salicylaldehyde or 2-hydroxy-1-naphthaldehyde, have been prepared and characterized by elemental analysis, magnetic susceptibility and IR and electronic spectral studies. The electrochemical behaviour of copper(II) and cobalt(II) complexes and ESR spectral parameters of all copper(II) complexes have also been examined. Ligand field strength increases with increase in chelate loop size from six to seven. The ESR spectral data reveal that the copper(II) complexes assume monomeric distorted octahedral or pseudo tetrahedral structures. The cyclic voltammetric redox potentials of copper(II) and cobalt(II) complexes suggest the existence of reversible Cu-II/Cu-I and Co-II/Co-I pairs in acetonitrile.