Synthesis, structures, and DFT analysis of gold complexes containing a thiosemicarbazone ligand

Abstract

In this study, we report the synthesis of a series of new gold compounds in different solvation media. First, gold(I) thiosemicarbazone (TSC) [Au–(TSC)₂]Cl was synthesized by reacting [Au(SMe₂)]Cl with a thiosemicarbazone ligand in acetonitrile. Then, we successfully managed to replace one of the monodentate thiosemicarbazone ligands with Cl to prepare the TSC–AuCl complex by the reaction of KAuCl₄ with thiosemicarbazone in acetonitrile. In a different strategy, the reaction of KAuCl₄ with thiosemicarbazone in methanol formed a [TSC–AuCl]AuCl₂ complex of tridentate (NNS) thiosemicarbazone. All complexes were fully characterized by X-ray diffraction, ¹H and ¹³C NMR spectroscopy, and mass spectrometry. The ¹H and ¹³C NMR spectra of the [Au–(TSC)₂]Cl in DMSO-d₆ solution showed two sets of signals, suggesting the presence of two complexes formed from (E)- and (Z)-TSC, respectively. X-ray studies showed only one complex from (Z)-TSC, and the (Z)-TSC ligands provide an exactly linear coordination arrangement around the Au(I) centres. X-ray crystallography showed [TSC–AuCl]⁺ cations in the AuCl₂ salts to have a square pyramidal geometry. Complexes of TSC–AuCl and [TSC–AuCl]AuCl₂ had limited stability, decomposing rapidly in solution, while the [Au–(TSC)₂]Cl complex was stable in solution.