Effect of the amide groups on superoxide dismutation catalyzed by copper(II) complexes of adamantane

Four copper(II) complexes (1, [Cu(L-1)(CH3COO-)](ClO4); 2, [Cu(L-2)(2)](ClO4)(2); 3, [Cu(L-2)(2)Br] Br and 4, [Cu-2(L-2)(2)(CH3COO-)(4)]; L-1 = N,N'-bis(2-pyridylmethyl)amantadine, L-2 = (pyridyl-2-amino)carbonyl adamantane) have been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. Copper ions in 1 and 2 have the distorted planar coordination configuration. The coordination geometry of 3 and 4 can be described as the distorted tetragonal pyramid. The adjacent two copper ions in 4 are bridged by four acetate anions. By using NBT assay at pH 7.8, the superoxide dismutase (SOD)like activity (IC50) of 1-4 were measured to be 0.21, 0.15, 0.22 and 0.90 mu M, respectively. The enhancement in SOD-like activity of 2 suggests that the hydrogen bonds provided by the amide groups and the coordination configuration play an important role on the dismutation of O-2(center dot-). Moreover, electrochemistry of complexes was determined by the cyclic voltammetry. (C) 2014 Elsevier B.V. All rights reserved.