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

Some processes of interaction between AuCl2- and glutathione with the formation of polymeric (-AuGSHi-)nn(i-2)+ and monomeric Au(GS)2Hii-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 (-AuGSH2-)n. The dependence of its solubility upon pH has been investigated. The substitution equilibria, Au(GS)25-+S2O32-⇌Au(GS)S2O34-+GS3-, log₁₀ β₁ = − 4.5 ± 0.3, and Au(GS)25-+2S2O32-⇌Au(S2O3)23-+2GS3-, 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 AuCl4- 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.