Structure and antioxidant superoxide dismutase activity of copper(II) hydrazone complexes

Three new mixed ligand hydrazone complexes viz., [Cu(L)(neocuprin)]NO3 center dot H2O 1, [Cu(L)(HL)]ClO4 2 and [Cu-2(2-(2-pyridyl)benzimidazole)(2)(L)(2)]ClO4 3 (L = N'-[(E)-phenyl(pyridin-2-yOrnethylidene]furan-2-carbohydrazide) have been synthesized by the biomimetic synthesis strategy and their structures were determined by single crystals X-ray analysis. The effect of differing contagious, as well as the rotational conformational versatility of HL, was demonstrated by the difference in structures of complexes 1-3. These complexes exhibited the antioxidant superoxide dismutase enzymatic activity. The geometry of copper(II) atom in complex 1 is distorted square pyramidal while in complexes 2 and 3 the geometries around copper(II) atoms are distorted octahedral. Magnetic measurements and epr spectroscopy of binuclear complex 3 have shown antiferromagnetic exchange interaction with a coupling constant (J) = -10.87 cm(-1). Electronic and spectral properties of these newly synthesized hydrazone complexes (13) are interpreted by DFT and TDDFT calculations. The results reveal that molecular structures have significant effect on antioxidant superoxide activity. Such biological experimental values (antioxidant SOD activity data) are indicative of the promising application of these complexes into the bioinorganic chemistry of superoxide dismutase. (C) 2016 Elsevier Ltd. All rights reserved.