Synthesis, superoxide dismutase, nuclease, and anticancer activities of copper(II) complexes incorporating bis(2-picolyl)amine with different counter anions

Interaction of the tridentate ligand bis(2-picolyl)amine L with copper(II) salts gave a series of copper(II) complexes with the formula types: [LCu(X)(2)] (X = Cl- 1, = Br- 2), [(LCu(H2O)(mu-SO4)(LCu(H2O)]SO4 3, [LCu(OAc)](OAc)H2O 4, [LCu(H2O)(2)](Y)(2) (Y = NO3-, = ClO4- 6). Their structures and properties were characterized by elemental analysis, thermal analysis (TGA), IR, UV-vis and ESR spectroscopy, electrochemical measurements including cyclic voltammetry and electrical molar conductivity, and magnetic moment measurements. A square pyramidal geometry is proposed for the halogeno complexes 1 and 2 in monomeric structures. For sulfate complex, the sulfate group bridged two copper(II) ions of the two [N3O] donor units to give the dimeric complex molecule 3 in square pyramidal environment around the copper(II) ions. In the case of complexes 4-6, square planar stereochemistries in monomeric structures are suggested. The SOD biomimetic catalytic activity of the obtained complexes was assessed for their ability to inhibit the reduction of nitroblue tetrazolium (NBT). The catalytic efficiency of O-2(-) scavenging by complexes depends on the nature of the particular acidic anion radical incorporated in the complex molecule and follows the order: NO3- > ClO4- > Br- >= Cl- > SO4- > AcO-. A probable mechanistic implications for the catalytic dismutation of O-2(-) by copper(II) complexes are proposed. Furthermore, complex 1 exhibits significant hydrolytic cleavage of the genomic DNA in the absence of any external additives. In addition, the in vitro study of cytotoxicity of complex 1 on colon cancer cell line (Caco-2) indicates that the complex has the potential to act as an effective anticancer drug with IC50 value of 156 +/- 0.35 mu M. (C) 2011 Elsevier B.V. All rights reserved.