Synthesis, characterisation, cytotoxicity and antibacterial activity of ruthenium(II) and rhodium(III) complexes with sulfur-containing terpyridines

Abstract

The synthesis and characterisation of novel thioacetyl-functionalised terpyridine ligands and their ruthenium and rhodium complexes [Ru(tpy)2](PF6)2, [Rh(tpy)2](PF6)3, [Ru(phen)(tpy)Cl](PF6), [Rh(phen)(tpy)Cl](PF6)2 (phen=phenanthroline; tpy=S-[ω-(2,2:6′,2″-terpyridin-4′-yl)phenoxy]alkyl ethanethioate) have been described. Ligands and complexes were characterised by 1H NMR spectroscopy, mass spectrometry, elemental analysis and cyclic voltammetry data. The crystal structure of the complex [Rh(phen)(tpy)Cl](PF6)2 (phen=phenanthroline; tpy=4′-phenyl-2,2′:6′,2″-terpyridine) (21), have been determined by X-ray crystallography. Complex 21 show a distorted octahedral geometry around the ruthenium centre. Antimicrobial activity toward Escherichia coli at concentrations as low as 5μM was found for some of the studied complexes. For complexes [Rh(tpyC6H4O(CH2)8SCOCH3)2](PF6)3 (19), [Rh(phen)(tpyC6H4O(CH2)8SCOCH3)Cl](PF6)2 (31) and [Rh(phen)(tpyC6H4O(CH2)11SCOCH3)Cl](PF6)2 (32), a strong inhibition of in vitro protein synthesis was observed using firefly luciferase. An investigation of cytotoxicity of the complexes against human embryonic kidney cells (HEK293 line) by the MTT assay demonstrates that the toxicity of all tested compounds is of similar magnitude, with IC50 values of 3–30μM.