Binuclear Ruthenium (II) Complexes Featuring Arylthiourea Ligands: Synthesis, Crystal Structure and Anticancer Assessment

A new set of arene binuclear Ru (II)complexes of the type [RuCl₂(η⁶-p-cymene)(η²-N^S-aroylthiourea)] has been synthesised to examine the effect on the cytotoxicity against human cancer cell lines. The formation of all the complexes (TC1–TC3) has been established with the aid of analytical and spectroscopic (infrared, UV–visible, NMR and mass) methods. The molecular structure of one of the complexes (TC1) was authenticated by single-crystal X-ray diffraction technique and concluded that the thiourea coordinated to each ruthenium (II) ion via hydrazine nitrogen and thiol sulphur to form a pseudo octahedral geometry around the ruthenium ions. Further, the antiproliferative activity of the complexes was evaluated with the help of MTT assay against human cancer cell lines such as HeLa (cervical cancer), MDA-MB-231 (breast cancer) and noncancerous L929 (mouse fibroblast) cell lines with the standard drug cisplatin. All the complexes exhibit significant cytotoxicity against cancel cell lines selected, and the highest was observed in the HeLa cell line, which articulates the specificity of these complexes towards the HeLa cancer cell line. Among them, complex TC2 shows high inhibitory effect with low IC₅₀ values against all the cancer cell line tested. This may be due to the presence of an electron-releasing methyl substituent of the ligand, which subsequently increased hydrophobicity. In addition, the apoptotic cell death mechanism of the all the complexes in HeLa cells was evaluated by biochemical assays such as AO-EB, DAPI and flow cytometry assays.