Design, Synthesis, DNA/HSA Binding, and Cytotoxic Activity of Half-Sandwich Ru(II)-Arene Complexes Containing Triarylamine–Thiosemicarbazone Hybrids

Organoruthenium complexes are potent alternatives for platinum-based complexes because of their superior anticancer activity. In this investigation, a series of new Ru­(II)-arene complexes with triarylamine–thiosemicarbazone hybrid ligands with higher anticancer activity than cisplatin are reported. The molecular structure of the ligands and complexes was confirmed spectroscopically and supported by single-crystal X-ray crystallography. These complexes adopted a three-leg piano stool geometry. All the Ru­(II)-arene complexes were systematically investigated for their in vitro cytotoxicity against human cervical (HeLa S3), lung (A549) cancer, and human normal lung (IMR-90) cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Interestingly, a pyrrolidine-attached Ru­(II)-benzene complex exhibited superior activity against cancer cells with low IC₅₀ values, and colony formation study showed complete inhibition at 5 and 10 μM concentration. Furthermore, morphological changes assessed by acridine orange and propidium iodide staining revealed that the cell death occurred by apoptosis. In addition, the interaction between synthesized Ru­(II)-arene complexes and DNA/protein was explored by absorption and emission spectroscopy methods. These synthesized new organoruthenium complexes can be used for developing new metal-based anticancer drugs.