Synthesis, Characterization and Electrochemical Behaviour of Some Manganese and Copper Complexes with Tetradentate Schiff Base Ligands

Abstract

A series of symmetrical tetradentate Schiff bases derived from substituted salicylaldehyde and ethylenediamine were prepared and characterized by elemental analysis, IR, UV-Visible and ¹H NMR spectroscopy. The interaction of these bases with MnCl₂ 4H₂O and CuCI₂ 2H₂O have been studied, leading to the preparation of manganese(II) and copper(II) complexes. Microanalysis, molar conductance, IR, UV-Visible spectroscopy, magnetic measurements and ESR spectra have been used to elucidate the stucture of the resultant complexes The experimental data show that all the Schiff base Iigands N, N′-bis(2-hydroxybenzyl)ethylenediimine (H₂L.¹), N, N′-bis(2-hydroxyacetophenyl)ethylenediimine (H₂L²) and N, N′-bis(2-hydroxypropiophenyi)ethylenediimine (H₂L³) yield 1:1 compounds except for the ligand H₂L² which gave a 2:1 compound with manganese(II) The spectral studies support the binding of the Iigands with two N. and two O donor sites to the metal(II) ion, giving an arrangement of N₂O₂ donor groups Magnetic and ESR data indicate that the manganese(II) adopts a high spin configuration in the complexes studied and the covalent character of the metal-ligand bonding in the copper(II) complexes increases with the increasing electron donating effect of the ligand substituents R. The electrochemical behaviour of the manganese(II) and the copper(II) complexes was determined by cyclic voltammetry which shows that the chelate structure and electron donating effects of the ligand substituents are among the factors influencing the redox potentials of the complexes