Synthesis, spectroscopic characterization and cytotoxicity studies of new potential anticancer chemotherapeutics, cis-dioxidomolybdenum(VI) compounds with substituted polypyridyl ligands

• four cis -dioxidomolybdenum(VI) complexes were synthesized using bidentate polypyridyl ligands. • cis -dioxidomolybdenum(VI) complexes showed lower IC 50 values than their corresponding ligands. • MoO 2 Cl 2 -[(4,7-dimethyl)-1,10-phen] presented a remarkable activity for the cell line U87MG. • MoO 2 Cl 2 -[(4,7-dimethyl)-1,10-phen] is a promising compound for further anticancer research. In this study, four cis -dioxidomolybdenum(VI) complexes were synthesized employing the ligands 4,4′-dimethyl-2,2′-bipyridine (L1) and 4,7-dimethyl-1,10-phenanthroline (L2) as model systems of bidentate polypyridyl ligands. The complexes were characterized by IR, UV–Vis and NMR spectroscopic techniques, while their elemental compositions were confirmed by elemental analysis. Additionally, the redox behaviour of the complexes and their respective ligands was investigated via cyclic voltammetry revealing the reduction processes Mo(VI) to Mo(V) and Mo(V) to Mo(IV) in the metal center. The cytotoxic activity of these compounds were evaluated in three human cancer cell lines: prostate adenocarcinoma (PC3), glioblastoma astrocytoma cell line (U87MG), and lung carcinoma cell line (A549) using methyl tetrazolium (MTT) assay. Flow cytometric analysis was conducted to elucidate the mechanism of cell death induced by the tested complexes. Results demonstrated that the L2 ligand exhibited higher cytotoxic effect than L1 after 48 h of exposure across all three cell lines A549, U87MG and PC3. Moreover, all cis -dioxidomolybdenum(VI) complexes showed lower IC 50 values than their corresponding ligands, indicating enhancement in cytotoxicity activity upon metal coordination. Notably, the dichloridodioxido-[(4,7-dimethyl)-1,10-phenanthroline]molybdenum(VI) exhibited remarkable potency against U87MG cells (IC 50 = 0.3 ± 0.1 µM), identifying it as promising drug candidate for further anticancer research.