Synthesis, characterization and biological properties of Ruthenium(II) polypyridyl complexes containing 2(1H)-quinolinone-3(1H-imidazo[4,5f][1,10]phenanthrolin-2-yl

Abstract

The ruthenium(II) complexes have been structurally characterised and their interaction with DNA, cytotoxicity and cellular uptake has been investigated. • Two water-soluble ruthenium(II) polypyridyl complexes were synthesized and characterized. • The complexes show solvent-dependent photophysical properties and are highly emissive in aqueous solutions. • The ruthenium(II) complexes exhibited moderate DNA binding ability. • Ruthenium(II) complexes are non-toxic towards HeLa cell line. • The ruthenium(II) complexes undergo rapid cellular internalization and localized throughout the cells. Two water-soluble ruthenium(II) polypyridyl complexes [Ru(bpy) 2 (qip)]Cl 2 ( 1 ) and [Ru(phen) 2 (qip)]Cl 2 ( 2 ) (where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, qip = 2(1H)-quinolinone-3(1H-imidazo[4,5f][1,10]phenanthrolin-2-yl) have been synthesized and structurally characterized. The experimental electronic spectral results obtained match well with the theoretical results obtained by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) studies. For both the complexes HOMO is mainly localized on the ancillary qip ligand, while HOMO-1 is mainly centered on the ruthenium atom with some contribution from all polypyridyl ligand. The LUMO is located on all polypyridyl ligands. Interaction of complexes with CT-DNA is explored by absorption and emission spectroscopic techniques. The complexes show solvent-dependent photophysical properties and are highly emissive in aqueous solutions compared to organic solvents. Both the complexes are non-toxic towards HeLa (human cervical cancer) and HEK293 (human embryonic kidney cell line) cell lines. Further, the cellular imaging properties of complexes 1 and 2 were investigated by fluorescence microscopy.