Synthesis, crystal structure, and SOD-like activity of two copper(II) complexes with hydroxymethyl pendants

Dinuclear and mononuclear copper(II) complexes (1, [Cu-2(HL)(2)(L)(2)](ClO4)(2); 2, [Cu(HL)(2)(phen)] (ClO4)(2), where HL = (N-methyl-2-methylol)imidazole, phen = 1,10-phenanthroline) have been synthesized and characterized by single crystal X-ray diffraction. The SOD-like activity (IC50) of 1 and 2 were measured to be 0.10 +/- 0.01 and 0.19 +/- 0.01 mu M by NBT assay at pH 7.8. The higher SOD activity of 1 could be contributed to the coordination configuration and the labile hydroxymethyl pendants. Electrochemistry and the frontier molecular orbital energies of the complexes were also studied. To mimic the active site of Cu, Zn-SOD, new copper(II) complexes (1, [Cu-2(HL)(2)(L)(2)](ClO4)(2); 2, [Cu(HL)(2)(phen)](ClO4)(2); where HL = (N-methyl-2-methylol) imidazole, phen = 1,10-phenanthroline) have been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. Copper(II) in 1 is four-coordinate by a N2O2 plane with two copper(II) ions bridged with two oxygens from the deprotonated hydroxylmethyl pendants. Each Cu2+ in 2 is coordinated by four nitrogens from two HL and one co-ligand of 1,10-phenanthroline. Electrochemistry of the complexes was studied by cyclic voltammetry. The atomic net charges distribution and frontier molecular orbital energies were obtained by Gaussian 98 program with DFT method at B3LYP/lanl2dz level. The SOD-like activity (IC50) of 1 and 2 were measured as 0.10 +/- 0.01 and 0.19 +/- 0.01 mu M by NBT assay at pH 7.8. The higher SOD activity of 1 could be attributed to the coordination configuration and the labile hydroxymethyl pendants.