On Redox Processes of Gold(III) Complexes with Biologically Important Thiols: Cysteine, Glutathione, Thiomalate

Abstract

AbstractThe interaction of a number of gold(III) complexes: Au(phen)X2+, Au(bipy)X2+ (X=Cl, OH, phen=1,10‐phenanthroline, bipy=2,2’‐bipyridile), Au(en)23+ and Au(dien)Cl2+ with anions of thiol‐containing acids (thiomalate, cysteine and glutathione) in an aqueous solution at pH 2.0 and 7.4, CNaCl=0.2 M was studied. In all cases, the products of gold(III) reduction were highly stable gold(I) thiolate complexes: polymeric Aum(RS)n or monomeric Au(RS)2, depending on the conditions. For bipy and phen complexes, the processes were fast and usually completed in less than 1 minute. For the complex with dien, the stage of inner‐sphere reduction was the slowest among the complexes under consideration. For this complex, at pH 7.4 and with a large excess of glutathione, the formation of a relatively long‐lived gold(III) complex was observed, which, according to MS data, has the composition Au(GSH)45–. At ordinary temperature, it decomposes by about 90 % in 20 hours. For other thiols, similar complexes are also formed, but the rate of their decomposition is about 10 times higher.