Synthesis, Characterization and Magnetochemical Studies of Some Copper(II) Complexes Derived from Tetrakis(N-Salicylidene)ethanetetracarboxylic Acid Tetrahydrazide

Abstract

Copper(II) complexes of a new salicylaldehyde tetrahydrazone, H8L derived from ethanetetracarboxylic acid tetrahydrazide, have been synthesized. Three types of copper(II) complexes Cu4(L).6H2O, Cu4(H4L)(NO3)4.7H2O and Cu4(H4L)Cl4.3H2O have been isolated and characterized by elemental analyses, infrared spectra, ultraviolet-visible spectra, as well as variable temperature magnetic susceptibility measurements. Magnetic susceptibility measurements of Cu4(L).6H2O and Cu4(H4L)(NO3)4.7H2O indicate significant antiferromagnetic coupling between copper(II) centers. The –2J values obtained from the Bleaney–Bowers equation equal 213 and 203 cm−1 suggest association of the coordinated copper(II) units Cu(ONO) via phenolic oxygen bridges. This gives rise to a polynuclear structure in which dimerization of coordinated acylhydrazone residues occurs. The chloro copper(II) complex Cu4(H4L)Cl4.3H2O also shows strong antifer-romagnetic exchange coupling (–2J = 472 cm−1), suggesting a polynuclear structure in which the copper(II) is in a distorted square-pyramidal environment, bound in the equatorial plane with a monomeric ONO tridentate acylhydrazone unit, and the bridged phenoxy oxygen and the axial site occupied by a chloride ion.