Anticancer Properties of Ru and Os Half-Sandwich Complexes of N,S Bidentate Schiff Base Ligands Derived from Phenylthiocarbamide

The versatile coordinating nature of N,S bidentate ligands is of great importance in medicinal chemistry imparting stability and enhancing biological properties of the metal complexes. Phenylthiocarbamide-based N,S donor Schiff bases converted into RuII/OsII(cymene) complexes and characterized by spectroscopic techniques and elemental analysis. The hydrolytic stability of metal complexes to undergo metal-halide ligand exchange reaction was confirmed both by the DFT and NMR experimentation. The ONIOM (QM/MM) study confirmed the histone protein targeting nature of aqua/hydroxido complex 2 aH with an excellent binding energy of -103.19 kcal/mol. The antiproliferative activity against a panel of cancer cells A549, MCF-7, PC-3, and HepG2 revealed that ruthenium complexes 1 a-3 a were more cytotoxic than osmium complexes and their respective ligands 1-3 as well. Among these ruthenium cymene complex bearing sulfonamide moiety 2 a proved a strong cytotoxic agent and showed excellent correlation of cellular accumulation, lipophilicity, and drug-likeness to the anticancer activity. Moreover, the favorable physiochemical properties such as bioavailability and gastrointestinal absorption of ligand 2 also supported the development of Ru complex 2 a as an orally active anticancer metallodrug.