On the Complexation of Gold(I) with Glutathione in Aqueous Solutions

Abstract

Some processes of interaction between $${\text{AuCl}}_{2}^{ - }$$ and glutathione with the formation of polymeric $$\left( {-{\text{AuGSH}}_{i}-} \right)_{n}^{n(i - 2) + }$$ and monomeric $${\text{Au}} ({\text{GS}})_2{\text{H}}_{i}^{i - 5}$$ gold(I) complexes in aqueous solutions at ionic strength of I = 0.2 mol·L−1 (NaCl) have been studied at 25 °C. The precipitate formed in the acidic region corresponds to the ordinary polymer $$\left( {-{\text{AuGSH}}_{2}-} \right)_{n}$$. The dependence of its solubility upon pH has been investigated. The substitution equilibria, $${\text{Au}}({\text{GS}})_{2}^{5 - } + {\text{S}}_{2} {\text{O}}_{3}^{2 - } \rightleftharpoons {\text{Au}}({\text{GS}}){\text{S}}_{2} {\text{O}}_{3}^{4 - } + {\text{GS}}^{3 - }$$, log10 β1 = − 4.5 ± 0.3, and $${\text{Au}}({\text{GS}})_{2}^{5 - } + 2{\text{S}}_{2} {\text{O}}_{3}^{2 - } \rightleftharpoons {\text{Au}}({\text{S}}_{2} {\text{O}}_{3} )_{2}^{3 - } + 2{\text{GS}}^{3 - }$$, log10 β2 = − 8.5 ± 0.2, have been studied and the effective protonation constants of the complexes have been determined. It is shown that under the action of $${\text{AuCl}}_{4}^{ - }$$ GSH is oxidized to sulfinic and sulfonic acids. The potential of using highly stable gold(I) complexes with glutathione as ligands, for metal ions having an affinity with respect to the amine nitrogen atom, has been established.