On Polymeric Gold(I) Complexes with Glutathione in Aqueous Solutions

The study addresses reactions involving gold(I) glutathione complexes in aqueous solutions at T = 25°C and I = 0.2 M (NaCl) in the pH range of 7.20–6.06 (CAu = (5–10) × 10–4 M). Using mass spectrometry, it was shown that at CGS > CAu, polymeric species $${\text{A}}{{{\text{u}}}_{{\text{4}}}}({\text{GS}})_{4}^{*}$$ and $${\text{A}}{{{\text{u}}}_{n}}({\text{GS}})_{{n + 1}}^{*}$$ , where n ≤ 4, can exist, together with monomeric $${\text{Au}}({\text{GS}})_{2}^{*}$$ (the symbol * means the sum of species with different degrees of protonation). According to UV spectroscopy data, in the range of 0.5 < CGS/CAu < 3, all spectra can be described, within the experimental error, as linear combinations of the spectra of four species, including $${\text{Au}}({\text{GS}})_{2}^{*}$$ . The proportion of $${\text{Au}}({\text{GS}})_{2}^{*}$$ decreases with decreasing pH. The equilibrium constant for 0.25 $${\text{A}}{{{\text{u}}}_{{\text{4}}}}({\text{GSH}})_{4}^{{4 - }}$$ + $${\text{GSH}}_{2}^{ - }$$ = $${\text{Au}}({\text{GSH}})_{2}^{{3 - }}$$ + H+ amounts to log K = –4.4 ± 0.1 (I = 0.2 M, NaCl).