Synthesis, Structure, and SOD-like Activity of a Copper(II) Complex Containing a Bistriazole Group

The dinuclear complex [Cu-2(HL)(2)(H2O)(2)](ClO4)(2) (1) [H2L = 5'-(pyridin-2-yl)-1-H,2'-H-3, 3'-bis(1, 2,4-triazole)] was obtained and fully characterized. It exhibits a centrosymmetry configuration, in which each copper(II) ion is pentacoordinate with four nitrogen atoms of two triazole ligands and one oxygen atom from a water molecule. The net atomic charges distribution and atomic orbital contribution to frontier molecular orbitals were obtained using the Gaussian 98 program with Hartree-Fock method at LANL2DZ level, indicating that the copper(II) ion has the potential to accept the electron of O-2(center dot-). The complex showed quasi-reversible one-electron Cu-II/Cu-I redox waves with redox potentials of -0.034 V. The SOD-like activity (IC50) of 1 was measured to be 0.18 +/- 0.01 mu M by xanthine/xanthine oxidase-NBT assay at pH 7.8. The relatively high SOD activity suggests that the positive charge of protonated triazole can effectively steer O-2(center dot-) to and from the active copper ion.