Abstract

Electron paramagnetic resonance studies were performed with nitrogen and sulfur containing chelators of Cu(II) ranging from a vic-dicarbonyl bis-thiosemicarbazone, through butyraldehyde thiosemicarbazone, to penicillamine and cysteine. In the former two cases, stable complexes were formed with a great deal of charge delocalization throughout the chelate ring structures as a result of pseudoaromaticity. In the latter two cases, in which ring electron delocalization is not possible, the unstable Cu(II) complexes are formed, ultimately yielding Cu(I) and oxidized chelator. This reaction, which we term "reductive chelation," is described as a probable mechanism for the mobilization of copper with penicillamine in patients with Wilson’s disease.