Synthesis, characterisation and cytotoxic activity of organoruthenium(II)-halido complexes with 1H-benzimidazole-2-carboxylic acid.

Three new ruthenium(II)–arene halido complexes of general formula [(η 6 - p -cymene)RuX(L)] ( C1 C3 ) were synthesised by reaction of [(η 6 - p -cymene)RuX 2 ] 2 (X − = Cl − , Br − , I − ) with 1 H -benzimidazole-2-carboxylic acid (HL) in ethanol. The complexes were characterised by elemental analysis, mass spectrometry, IR, 1 H and 13 C NMR spectroscopy. The 1 H -benzimidazole-2-carboxylate was found to act as a bidentate N,O–chelating ligand. Single-crystal X-ray diffraction analysis confirmed the “piano-stool” geometry of C3 . The cytotoxic activity of the ligand precursor and ruthenium complexes was tested in human cancer cell lines: cervical carcinoma (HeLa), breast carcinoma (MDA-MB-231), myelogenous leukemia (K562) as well as in one normal human fetal lung fibroblast cell line (MRC-5), by MTT assay. The results show that ruthenium(II)-arene complexes possess enhanced cytotoxicity when compared to that of HL. The latter was devoid of activity in the range of concentrations up to 300 μM. Complex C3 , carrying an iodido leaving ligand, exhibited moderate, but selective cytotoxicity toward HeLa, MDA-MB-231 and K562 cell lines, with IC 50 values: 73.7, 60.9 and 53.9 μM, respectively, being less toxic against MRC-5 cells (IC 50 = 175.9 μM). Complexes C1 and C2 showed moderate to low cytotoxicity in HeLa and K562 cells. [ABSTRACT FROM AUTHOR]