Carboxylate-bridged copper(II) complexes: synthesis,crystal structures,and superoxide dismutase activity

Two copper(II) complexes, Cu₂(μ-benzoato)(L¹)₂]NO₃·2H₂O (1) and Cu₂(μ-succinato)(L²)₂(H₂O)]ClO₄ (2), have been synthesized, where L¹ = N′-(E)-phenyl(pyridin-2-yl)methylidene]benzoylhydrazone and L² = N′-(E)-pyridin-2-ylmethylidene]benzoylhydrazone. These complexes were characterized including by single-crystal X-ray diffraction studies. The copper is five-coordinate in 1 while in 2 one copper is five-coordinate and the other is six-coordinate. Electrochemical behavior of these complexes was measured by cyclic voltammetry. The conproportionation equilibrium constants (K_con) for both complexes have been estimated. The superoxide dismutase (SOD) activities of 1 and 2 were measured by nitro blue tetrazolium assay. Complex 1 has better SOD activity than 2.