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

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.