Ruthenium(II)–arene complexes with substituted picolinato ligands: Synthesis, structure, spectroscopic properties and antiproliferative activity

A series of seven new ruthenium(II)–arene complexes of general formula [Ru(η6-p-cymene)(L1−7)Cl], where L1−7 are fluoro, chloro, bromo or methyl derivatives of picolinic acid or isoquinoline-3-carboxylic acid has been synthesized and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy and ESI mass spectrometry. X-ray diffraction studies of two compounds showed the usual piano-stool geometry, with coordination of picolinato ligands through the pyridine nitrogen and the carboxylic group oxygen atom (N/COO− donor set). Cytotoxicity of complexes in vitro has been evaluated in three human tumor cell lines: cervix carcinoma (HeLa), melanoma (FemX), lung adenocarcinoma (A549) and one normal cell line (MRC-5). Complex with isoqinoline-3-carboxylic acid as ligand, exhibited significantly lower cytotoxic activity in normal cells (MRC-5) against high activity observed in panel of tumor cells and prominent cell type selectivity among tumor cells.