Synthesis, characterization, and oxidase activities of copper(II) complexes of the anticonvulsant drug valproate

Abstract

The interaction of binuclear copper(II) complex of the anticonvulsant drug valproate, Cu2(valp)4 (1), with metronidazole (mtnd) or 2-methyl-5-nitrobenzimidazole (2m5nbnz), have led to the isolation of two binuclear adducts of the type Cu2(valp)4(mtnd)2 (2), and Cu2(valp)4(2m5nbnz)2 (3), and one mononuclear adduct of the type Cu(valp)2(2m5nbnz)2 (4). Spectral and magnetic data and preliminary X-ray measurements for complexes 2 and 3 are consistent with a binuclear structure as found for copper(II) tetracarboxylate adducts. The above data for complex 4 are consistent with a mononuclear square planar complex that contains two valproate ligands and two N-containing 2m5nbnz ligands to give essentially a trans-CuN2O2 chromophore. The catalytic activities of the complexes toward the aerobic oxidation of 3,5-di-t-butycatechol to the corresponding o-benzoquinone and N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) to TMPD+ were determined. The activities were found to be in the order 1 > 2 > 3 > 4. The formation of a copper ion-semiquinone species in solution, which may be the catalytic intermediate that reacts directly with oxygen, was demonstrated spectrophotometrically.