Water-Soluble Mono- and Binuclear Ru(η6-p-cymene) Complexes Containing Indole Thiosemicarbazones: Synthesis, DFT Modeling, Biomolecular Interactions, and In Vitro Anticancer Activity through Apoptosis

Indole thiosemicarbazone ligands were prepared from indole-3-carboxaldehyde and N-(un)substituted thiosemicarbazide. The Ru(η6-p-cymene) complexes [Ru(η6-p-cymene)(HL1)Cl]Cl (1) and [Ru(η6-p-cymene)(L2)]2Cl2 (2*) were exclusively synthesized from thiosemicarbazone (TSC) ligands HL1 and HL2, and [RuCl2(p-cymene)]2. The compounds were characterized by analytical and various spectroscopic (electronic, FT-IR, 1D/2D NMR, and mass) tools. The exact structures of the compounds (HL1, HL2, 1, and 2*) were confirmed by single-crystal X-ray diffraction technique. In complexes 1 and 2*, the ligand coordinated in a bidentate neutral (1)/monobasic (2*) fashion to form a five-membered ring. The complexes showed a piano-stool geometry around the Ru ion. While 2* existed as a dimer, 1 existed as a monomer, and this was well explained through free energy, bond parameter, and charge values computed at the B3LYP/SDD level. The intercalative binding mode of the complexes with calf thymus DNA (CT DNA) was revealed by spectrosc...