Autoxidation of thiol-containing amino acid to its disulfide derivative that links two copper(II) centers: the important role of auxiliary ligand.

Treatment of Cu(AcO)(2) with D-penicillamine or L-cysteine in the presence of 2,2'-bipyridine afforded dicopper(II) complexes with a bis(bidentate-N,O) disulfide ligand, the formation mechanism of which was discussed on the basis of Cu(II)-thiolate interaction affected by an auxiliary ligand.