Study of Silver(I) Complex Formation with Some Thiourea Derivatives in Aqueous Solution
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y of Silver(I) Complex Formation with Some Thiourea Derivatives in Aqueous Solution A. S. Samadova,*, I. V. Mironovb, I. G. Goricheva, O. V. Kovalchukovac, and A. F. Stepnovaa a Moscow
b
State Pedagogical University, Moscow, 129164 Russia A.V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090 Russia c Russian University of Friendship of Peoples, Moscow, 115419 Russia *e-mail: [email protected] Received May 7, 2020; revised June 29, 2020; accepted July 7, 2020
Abstract—The equilibrium processes of the formation of mononuclear and some binuclear silver(I) complexes with thiourea, N-acetylthiourea, thiosemicarbazide, N-phenylthiourea, and N,Nʹ-diphenylthiourea at 25°C and I = 0.11 M. (0.01 M HNO3 + 0.1 M NaNO3) in aqueous solution were studied by potentiometry method with a silver electrode. The stability constants of the complexes were determined. The stability of mononuclear complexes is almost identical for all the ligands, except for complexes with acetylthiourea, for which it is lower. Keywords: complexation, silver(I) ions, thiourea derivatives, stability constant, potentiometry
DOI: 10.1134/S1070363220110146 Complex compounds of silver(I) with thiourea derivatives exhibit biologically activity, including antibacterial [1] and antitumor [2-4]. It is assumed that these properties are largely determined by the complex formation of silver(I) ions with N,S-donor ligands that exhibit a wide range of biological activity [3, 5, 6]. In addition, thiourea and its derivatives are used in the extraction of precious metals, including silver, from various raw materials [7–11]. Despite the diverse use of coordination compounds of thiourea and its derivatives, data on the stability of metal complexes with these ligands in solution are severely limited. Information about the stability constants of complex silver(I) compounds with N- and N,N′substituted thiourea is particularly scarce. The equilibria of formation of silver(I) complexes with thiourea were studied in [12–16]. Stable mono[Eq. (1)] and binuclear [Eq. (2)] complexes are formed in the system of silver(I) complexes with thiourea. Ag+ + i L = AgLi+, β1i, 2Ag+
+iL
= Ag2Li2+,
β2i.
(1) (2)
In mononuclear complexes, the ligand is coordinated to the silver(I) atom via the sulfur atom; in binuclear complexes, one of the sulfur atoms is bridging. The Ag2L32+ binuclear complex is the most stable. With a
decrease in cAg, despite the increase in the fraction of mononuclear complexes, the binuclear forms retain a significant contribution to the material balance. For silver(I) complexes with thiourea derivatives, similar equilibria are assumed, because the substituents are not directly bound to the donor S atom, and there is no reason to expect significant changes in the coordination mode. Thiourea derivatives are widely used in biology, as corrosion inhibitors, in the extraction of precious and non-ferrous metals from various media and raw materials [11]. Having approximately the same ability to complex forma
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