Mechanism of complex formation between [AuCl4] and l-methionine |
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| Authors: | A.V. Vujačić,J.Z. Savić,S.P. Sovilj,K. Mé szá ros Szé csé nyi,N. Todorović,M.Ž. Petković,V.M. Vasić |
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| Affiliation: | 1. Department of Physical Chemistry, Vin?a Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia;2. University of Belgrade, Faculty of Chemistry, P.O. Box 158, 11000 Belgrade, Serbia;3. University of Novi Sad, Faculty of Sciences and Mathematics, Department of Chemistry, 21000 Novi Sad, Trg D. Obradovi?a 3, Serbia;4. Institute for Chemistry, Technology and Metallurgy, Studentski trg 12-16, 11000 Belgrade, Serbia |
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| Abstract: | The kinetics of the reaction between the tetrachloroaurate(III) ion and l-methionine (l-Met) (0.1 M HClO4, pH 1.0–2.5) have been studied spectrophotometrically using a stopped-flow technique at different temperatures. Initially, the fast substitution reaction was ascribed to the formation of the short-lived square-planar Au(III)–(l-Met) that was followed by the replacement of a Cl− ligand and a subsequent, slower reduction to Au(I)–(l-Met). This is an intermolecular process, involving attack on the [AuCl4]− complex by an outer-sphere l-methionine. The activation parameters (ΔH≠ and ΔS≠) for substitution and reduction were determined. IR spectroscopy indicates that l-methionine acts as a bidentate ligand, most likely coordinating via the S and N atoms, while 1H and 13C NMR data indicate methionine sulfoxide as the final product. Finally, the components of the reaction were treated thermally in order to investigate the solid phase synthesis of the resulting complex. |
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| Keywords: | Gold(III) l-Methionine Complex formation Kinetics |
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