Synthesis, structure and anticancer activity of (η6-benzene) ruthenium(II) complexes containing aroylhydrazone ligands

Abstract

New benzene ruthenium(II) aroylhydrazone complexes of general molecular formula [Ru(η6–C6H6)Cl(L)] (where L = aroylhydrazone ligand) have been synthesized from the reaction of the precursor [Ru(η6–C6H6)(μ-Cl)Cl]2 and aroylhydrazone ligands. The composition of the complexes has been accomplished by elemental analysis and spectral methods (FT-IR, UV-Vis, 1H NMR). The molecular structure of complex 4 has been established by single-crystal X-ray structure analysis shows that the aroylhydrazone ligands are coordinated to ruthenium as a bidentate N, O donor and a typical piano stool geometry was observed around ruthenium(II) metal center. All the complexes exhibit two consecutive irreversible oxidations in the potential range +0.74 to +1.17 V (RuII/RuIII;RuIII/RuIV) Vs calomel electrode. Further, in vitro anticancer activity of complexes 1–4 on human breast cancer cell line (MCF-7), human cervical cancer cell line (HeLa) and non-cancerous NIH-3T3 cell line exhibit moderate to excellent cytotoxic activity. It is also evident from IC50 values that the complexes are more potent against MCF-7 cells than cisplatin. The superior activity of the complex 4 assumes that presence of electron donating methoxy substituent which makes the ring more reactive. Further, the morphological changes during cell death were investigated by Acridine Orange-Ethidium Bromide (AO–EB) and DAPI staining techniques, which confirm the complex 4 induces cell death only through apoptosis.