Gold(I) cysteinate complexes in aqueous solutions


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Abstract

Equilibria between gold(I) cysteinate complexes in aqueous solutions are studied by pH-metry, solubility measurements, and potentiometric measurements using a gold electrode at 25°C and I = 0.2 M (NaCl). The stepwise protonation constants logKiH of cysteinate Hi – 1Cysi – 3 + H+ = HiCysi – 2 are as follows: 10.10 (i = 1), 8.12 (i = 2), and 1.90 (i = 3). Protonation of cysteinate complexes is studied: Au(Cys)23− + H+ = Au(HCys)(Cys)2–, logK1H Au = 9.62 and Au(HCys)(Cys)2– + H+ = Au(HCys)2, logK2HAu = 9.01. The constant KS of the heterogeneous equilibrium Au(HCys)s + HCys = Au(HCys)2 is 3.3. The standard potential of the Au(Cys)23− complex is E1/00 = –0.172 ± 0.011 V. The stability of the Au(HCys)2 complex is close to that of Au(HS)2. The constant of substitution Au(HCys)2 + SO32− = Au(HCys)SO32− + HCys is determined to be logK11H = –1.3.

About the authors

I. V. Mironov

Nikolaev Institute of Inorganic Chemistry, Siberian Branch; Novosibirsk National Research State University

Author for correspondence.
Email: imir@niic.nsc.ru
Russian Federation, Novosibirsk, 630090; Novosibirsk, 630090

V. Yu. Kharlamova

Nikolaev Institute of Inorganic Chemistry, Siberian Branch; Novosibirsk National Research State University

Email: imir@niic.nsc.ru
Russian Federation, Novosibirsk, 630090; Novosibirsk, 630090

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