Synthesis, spectroscopic characterization, DFT studies and biological assays of a novel gold(I) complex with 2-mercaptothiazoline

A new gold(I) complex with 2-mercaptothiazoline (MTZ) with the coordination formula [AuCN(C3H5NS2)] was synthesized and characterized by chemical and spectroscopic measurements, DFT studies and biological assays. Infrared (IR) and 1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopic measurements indicate coordination of the ligand to gold(I) through the nitrogen atom. Studies based on DFT confirmed nitrogen coordination to gold(I) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Thermal decomposition starts at temperatures near 160 °C, leading to the formation of Au0 as the final residue at 1000 °C. The gold(I) complex with 2-mercaptothiazoline (Au–MTZ) is soluble in dimethyl sulfoxide (DMSO), and is insoluble in water, methanol, ethanol, acetonitrile and hexane. The antibacterial activities of the Au–MTZ complex were evaluated by an antibiogram assay using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of the cytotoxic effect of the Au–MTZ complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a potent cytotoxic activity, inducing 85% of cell death at a concentration of 2.0 μmol L−1.

Graphical abstractGeometric parameters for the gold(I) complex with mercaptothiazoline: Au (yellow); N (blue); S (light yellow); C (gray) and H (white).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel gold(I) complex with 2-mercaptothiazoline. ► IR, 1H, 13C and 15N NMR studies permitted to confirm nitrogen coordination. ► The compound shows biological activities against Gram-negative and positive bacteria. ► The complex also exhibits cytotoxic activities against HeLa tumorigenic cells.