Synthesis, characterization and demonstration of superoxide dismutase-like activity of copper(II) chloride, bromide, nitrate, thiocyanate, sulphate, and perchlorate complexes with 2-methyl-amino pyridine

Abstract

A number of copper(II) complexes containing 2-methyl amino pyridine and various anions (Cl −, Br −, NO 3 −, SCN −, ClO 4 −, or SO 4 2−) have been synthesized and characterized by elemental analysis, X-ray powder diffraction, IR, and electronic spectra. Molar conductivity and magnetic moment measurements were also employed. A square-pyramidal structure is proposed for the complexes in which chloride, bromide, nitrate, thiocyanate, or sulphate is attached to the metal ion in 1:2 (metal:ligand) stoichiometry. In the case of perchlorate complex, the molar conductivity and spectral data together suggest a square planar environment around the copper(II) ion. The catalytic activity of the prepared copper(II) complexes towards the superoxide anion O 2 − dismutation were assayed by their ability to inhibit the reduction of nitrobule tetrazolium (NBT). The catalytic efficiency of O 2 − scavenging by complexes depends on the particular acidic anion radical bound to the Cu(II) ion in complex and follows the order SO 4 > SCN > NO 3 > ClO 4 > Br ≥ Cl. The kinetic investigations reveal that the rate of O 2 − dismutation has a first-order dependence with respect to O 2 − and catalyst concentration. In addition, the rate constant of the catalytic dismutation of O 2 − varied between 2.8×10 5 and 5.9×10 6 mol −1 · S −1, dependence on the nature of complex.