Radical reductions of Cu(II)-penicillamine complexes: Evidence for a Cu(II)-disulphide anion intermediate

Abstract

Can. J. Chem. 69, 533 (1991).In basic solution Cu(I1) ions form plana!: complexes of stoichiometry Cu(II).L2 with penicillamine molecules, where both the nitrogen and sulphur atoms of the thiol [(NH2)CH(COz-)C(CH3)zS-] are involved in the coordination. The rates of reduction of this complex by the formate radical and the thiyl radical of penicillamine have been measured by pulse radiolysis.The rate constant for reaction [14] has been found to be 1.For the thiyl radical, which is not inherently reducing, reduction must involve the PenS:.SPen-anion complexUnder the conditions of this study, ([Pens-] -lo-' M , pH = 10.0), this anion exists in free solution equilibrium with Pens.A systematic study of the dependence of the overall reduction rate on [Pens-] showed that the reaction proceeded rapidly even when the PenS:.SPen-concentration was negligibly small. This finding can be explained by the formation of an internal PenS:.SPen-anion from the reaction of free Pens. with one of the Pens-ligands of the Cu(I1) complex:and the subsequent rapid transfer of an electron to Cu(l1):Analysis of the results gave k2 = 2.9 * 0.3 X 10' M-' s-' and k3 = 3.4 0.4 X 10' M-' s -' .

Catalytic Reduction of Fe(III)-cytochrome-cInvolving Stable Radiolysis Products Derived from Disulphides, Proteins and Thiols

“…We tentatively suggest that Cu e+ facilitates, by interacting with -SS' --anions, the carbon-sulphur bond scission via reaction (10) . Formation of Cu(ii)-disulphide anion intermediates seems to be established, but the subsequent decay in the case of penicillamine (Mezyk and Armstrong 1991) was proposed to occur just by electron transfer to Cu(n) . Further studies of the fate of protein -SS' --intermediates, particularly in the presence of electron acceptors, are necessary .…”

The kinetics and mechanism of the ligand substitution reaction of aquapentacyanoruthenate(II) with d-penicillamine in aqueous medium

“…21 On account of its excellent properties, D-PA has been used for the treatment of Wilson's disease by decreasing excess copper levels through reduction of Cu(II) to Cu(I), in heavy metal poisoning, in cystinuria, in rheumatoid arthritis, and also has several significant applications in biological systems. [22][23][24][25][26][27][28][29] In the past, ruthenium compounds have been widely employed as potential cytostatic agents as well as a possible alternative to drugs containing platinum metal. [30][31][32] Amino and cyano complexes of ruthenium metal, that is, [(NH 3 ) 5 RuL] 2 + and [(CN) 5 RuL] 3 + with pyrazine or pyridine aromatic heterocycles, 33 have been explored previously along with other pentacyano(ligand) complexes of Ru(II) [34][35][36][37] and Fe(II).…”