Catalytic activities of the antitumour complex bis(acetato)bis(imidazole)copper(II) and bis(valproato)bis(imidazole)copper(II) for the oxidation of organic substrates

Abstract

Abstract The catalytic activities of the antitumour complex bis(acetate)bis(imidazole) copper(II) (1) and bis(valproato)bis(imidazole)copper(II) (2) toward the aerobic oxi-dation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD ) to T M P D + and 3,5-di-t-butylcatechol (DTBC) to 3,5-dit-butylobenzoquinone were determined. The rates were found to be first order with respect to both substrate and catalyst concentration. Com - plexes 1 and 2 were found to be effective catalysts for the oxidation cyclization of o-phenylenediamine (OPD) to 2,3-diaminophenazine, as well as oxidation of hydroquinone to 1,4-benzoquinone. The formation of a copper ion semiquinone species in solution, which may be the catalytic intermediate that reacts directly with oxygen, was demonstrated spectrophotometrically. The results suggested that the oxidation of OP D and D T B C takes place in two one-electron transfer steps. The copper(II) complex/OPD/PPh3 catalyst system was found to catalyse the oxidation of triphenylphosphine (PPh3) to P h 3 P ~ by molecular oxygen. The relevance o f these copper(II) complexes to the biological functions of copper-containing proteins are discussed.