Superoxide dismutase activity of Cu(II) 2(aspirinate) 4 and its adducts with nitrogen and oxygen donors

Abstract

Several adducts of Cu(II) 2(aspirinate) 4 of formula [Cu(II)(aspirinate) 2L 2], where L is pyridine, nicotinamide, 3-picoline, 4-picoline, imidazole, 1-methyl- imidazole, diethylamine and dimethyl sulfoxide, have been synthesized. They show an absorption wavelength maximum between 690 and 750 nm, which is assigned to the d-d transition. The infrared spectra of these adducts indicate the bonding of nitrogen to copper in their nitrogen base adducts and the bonding of oxygen to copper in the DMSO adduct. The frozen ESR spectra of the adducts suggest that the ligands are bonded in an axial environment around copper with two nitrogen donors occupying the equatorial plane. The lower g∥ value of the DMSO adduct as compared to g∥ values of the nitrogen base adducts implies that there is bonding of the oxygen atom of DMSO in its adduct. The superoxide dismutase activity of several of these adducts has been measured. The pyridine adduct of Cu(II) 2(aspitinate) 4 shows a much higher activity than its DMSO adduct. This is also reflected in the enhanced antitumor activity of the pyridine adduct over the DMSO adduct of Cu(II) 2(aspirinate) 4.