Synthesis, characterization and in vitro cytotoxicity of Au(I) carbene complexes

Gold(I) N-heterocyclic carbenes (Au(I)-NHCs) are among the most widely investigated class of complexes exhibiting cytotoxic potential towards a wide range of cancers. We synthesized four new Au(I)–NHC complexes (1–4) by reacting (1,3-bis(2,6-di-isopropylphenyl)imidazol-2-ylidenegold(I)chloride) (Au(Ipr)Cl) with four different thiones, namely N-(i-propyl)imidazolidine-2-thione (i-PrImt), N-(di-propyl)imidazolidine-2-thione (i-Pr₂Imt), 1,3-Diazinane-2-thione (Diaz) and 1,3-Diazipane-2-thione (Diap). The synthesized Au(I)–NHC complexes (1–4) were fully characterized by elemental analysis (CHNS) and various spectroscopic techniques, including Fourier-transform infrared spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and ¹³C) and single crystal X-ray diffraction (XRD). Further, the newly synthesized Au(I)-NHCs (1–4) were evaluated for antitumor activity against human lung adenocarcinoma (A549), breast adenocarcinoma (MCF7) and human colorectal cancer (HCT15) cell lines using well established MTT Tetrazolium assay protocol. The complexes (1–4) showed moderate anticancer activities against selected cancer cell lines.