Persistence of oxidation state III of gold in thione coordination

Abstract

Ligands N,N´-tetramethylthiourea and 2-mercapto-1-methyl-imidazole form stable Au(III) complexes [AuCl 3 (N,N´-tetramethylthiourea)] (1) and [AuCl 3 (2-mercapto-1-methyl-imidazole)] (2) instead of reducing the Au(III) metal center into Au(I), which would be typical for the attachment of sulfur donors. Compounds 1 and 2 were characterized by spectroscopic methods and by X-ray crystallography. The spectroscopic details were explained by simulation of the UV-Vis spectra via the TD-DFT method. Additionally, computational DFT studies were performed in order to find the reason for the unusual oxidation state in the crystalline materials. The preference for Au(III) can be explained via various weak intra-and intermolecular interactions present in the solid state structures. The nature of the interactions was further investigated by topological charge density analysis via the QTAIM method. • Thione derivatives of gold were synthesized and characterized • Oxidation state III was atypically maintained • Computational TD-DFT studies were used to explain spectroscopic data • DFT and QTAIM methods were employed to clarify the oxidation state of the metal and the weak interactions in solid state

An Imidazole Thione-Modified Polyhedral Oligomeric Silsesquioxane for Selective Detection and Adsorptive Recovery of Au(III) from Aqueous Solutions

“…11 In addition, Au(III) has stronger oxidation ability than other metal ions (e.g., Cu(II), Fe(III), Ni(II), and Cd(II)), 49 and the redox process exists between the imidazole thione, thioether units, and Au(III) (see the details in the following part of Adsorption Mechanism). 37,52 Higher oxidation potential of Au(III) to imidazole thione and thioether units is a vital factor leading to a desirable selective adsorption (the redox process is shown in Scheme 2). Moreover, the pH effect in the range of 1−7 on the adsorption efficiency was investigated at the initial Au(III) concentrations of 100, 1000, and 2000 ppm.…”

“…This reduction process is probably induced by the soft nucleophile-sulfur compounds and Au(III), which has been proven in thioethers and monodentate heterocyclic thiones. 37 Apart from the reduction mechanism, the coordination interaction between Au(III) and sulfur atoms from thione or thioether groups in POSS-2 is another important adsorption mechanism, as evidenced by the variation of the binding energy of S2p in the XPS spectra of POSS-2 before and after Au(III) adsorption. Table S3 lists the binding energies of these atoms.…”

“…The fitted peaks at BEs of 161.54 and 162. 37,39 As shown in Scheme 2a, due to the intrinsic zwitterionic resonant structure of imidazole thione, the sulfur atoms become anionic and imidazole rings become cationic by charge delocalization. 36 Subsequently, a Au(III) attacks two anionic sulfur atoms of the imidazole thione group, leading to the reduction of the metal center to form the S−Au(I)−S moiety.…”