Synthesis and anticancer evaluation of trinuclear N^N quinolyl-benzimidazole-based PGM complexes

Abstract

• Trinuclear N^N quinolyl-benzimidazole-based PGM complexes were prepared. • Comprehensively characterised using various spectroscopic and analytical techniques. • Antiproliferative properties against two human breast cancer cell lines, MCF-7 and MDA-MB-32, were evaluated. • A ruthenium(II) p -cymene complex was found to be the most active complex. The synthesis, characterization and cytotoxicity of a novel tris-benzimidazole-quinoline hybrid ligand and its corresponding cationic trimetallic complexes are described. The synthesis of the ligand was achieved via an acid-catalyzed cyclization-condensation reaction of a tris-benzenediamine precursor with 2-quinolinecarboxaldehyde. The complexation reactions of the bidentate tris-ligand with the appropriate precursor dimers [Ru(η 6 -p-Pr i C 6 H 4 Me)Cl 2 ] 2 , [IrCp*( μ -Cl)Cl] 2 , [RuCl 2 (η 6 -C 6 H 5 OCH 2 CH 2 OH)] 2 and [Os(η 6 -p-Pr i C 6 H 4 Me)Cl 2 ] 2 afforded four new cationic trimetallic complexes. The complexes are moisture and air-stable and were characterized using various spectroscopic techniques ( 1 H, 13 C NMR spectroscopy and FT-IR spectroscopy). UV/Visible spectroscopic studies of the trinuclear metal complexes showed that the complexes are stable in DMSO for 48 h at room temperature and physiological temperature, and are thus compatible for in vitro experiments. The synthesized ligand and complexes were examined for antiproliferative properties against two human breast cancer cell lines: MCF-7 and MDA-MB-231. Preliminary evaluations of the test compounds were conducted at a single dose concentration of the test compounds. The osmium(II) and ruthenium(II) p -cymene complexes showed the greatest anticancer activity of all the synthesized compounds and were selected for multidose screening. The ruthenium(II) p -cymene complex was found to be the most active complex, with IC 50 values of 25.23 μ M and 32.68 μ M in the MCF-7 and MDA-MB-231 cell lines, respectively.