Binding of Gold(III) from Solutions Using Bismuth Hexamethylenedithiocarbamate: Double Complexes of Composition [Au(S2CNHm)2][Bi(S2CNHm)2Cl2] and [Au(S2CNHm)2]2[Bi2(S2CNHm)2Cl6] (Preparation, Crystal Structure, Thermal Behavior, and Anti-Mycobacterial Activity)

Abstract

It has been found that the reaction of bismuth hexamethylenedithiocarbamate (HmDtc) with an H[AuCl₄]/2 M HCl solution leads to formation of double complexes of composition [Au(S₂CNHm)₂][Bi(S₂CNHm)₂Cl₂] (I) and [Au(S₂CNHm)₂]₂[Bi₂(S₂CNHm)₂Cl₆] (II) as individual forms of gold(III) binding in the solid phase. The structures of the prepared compounds contain centrosymmetric/noncentrosymmetric (in I/II) Au(III) complex cations and heteroleptic bismuth anions: mononuclear and binuclear with ratio Bi : Dtc : Cl = 1 : 2 : 2/2 : 2 : 6 (I/II). Secondary S\( \cdots \)S and S\( \cdots \)Cl interactions between these ionic structural units result in formation of 3D supramolecular architectures. In the IR spectra of the compounds, the absorption bands of N–C(S)S bonds have been assigned to HmDtc ligands in the inner sphere of Au(III) complex cations and Bi(III) anions. Thermal behavior of compounds I and II has been studied by simultaneous thermal analysis. Residual substance obtained after thermolysis of samples consists of metallic particles of bismuth solid solution in gold coated with Bi₂O₃ layer. Complex I exhibits a high level of antimycobacterial activity in vitro toward non-pathogenic strain of Mycolicibacterium smegmatis.