Synthesis, in vitro anticancer activity and reactions with biomolecule of gold(I)-NHC carbene complexes

•Gold(I) N-heterocyclic carbene complexes containing 1,3-imidazolidine-2-thione and its four N-mono- and N,N’-dialkyl derivatives were synthesized and characterized.•The In vitro cytotoxicity of complexes was evaluated against three human cancer cell lines, HCT-15, A549 and MCF7.•The possible mechanism of interaction between complexes and biomolecule (L-Tyrosine) was investigated through electrochemical reactions monitored by Cyclic and Square Wave Voltammetry. Gold(I) N-heterocyclic carbene (NHC) complexes are widely investigated for promising anticancer activities. Herein, we present the synthesis, structural elucidation and in vitro cytotoxic profiles of five new gold(I)-NHC complexes containing thione ligands represented as [Au(IPr)(thione)]PF6 (where IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene and thione refers to 1,3-imidazolidine-2-thione (Ims) and its four N-mono- and N,N’-dialkyl (alkyl = -CH3, -C2H5) derivatives. Structural confirmation of all synthesized compounds has been carried out by elemental analysis, FTIR, 1H NMR and 13C NMR spectroscopy. Three out of five complexes (1, 3, 4) have also been subjected to single-crystal X-ray diffraction studies, which revealed the presence of [Au(IPr)(thione)]+ and PF6− as counter ions and close to linear coordination geometry of gold(I) atoms. In vitro antitumor studies of synthesized complexes were examined against human cancer cell lines of colon, lung and breast cancers, namely HCT-15, A549 and MCF7 using MTT assay. The electrochemical reactions were also performed to know the possible mechanism of interaction between complexes and biomolecule. Description: Structures of Gold(I)-NHC complexes with thione ligands. Graphs show interaction of one of the complexes with the L-tyrosine which was observed by the decrease of the oxidation peak current, change in oxidation peak potential and by decreasing the diffusion coefficient of the L-tyrosine. [Display omitted]