New π-arene ruthenium(II) piano-stool complexes with nitrogen ligands

The synthesis, characterization, DNA interaction and antiproliferative behavior of new π-arene ruthenium(II) piano-stool complexes with nitrogen ligands are described. Three series of organometallic compounds of formulae [RuCl2(η6-p-cym)L] were synthesized (with L = 2-, 3- or 4-methylpyridine; L = 2,3-, 2,4-, 2,5-, 3,4-, 3,5-dimethylpyridine and L = 1,2-, 1,3- 1,4-methylaminobenzene). The crystal structures of [RuCl2(p-cym)(4-methylpyridine)], [RuCl2(p-cym)(3,4-dimethylpyridine)] and [RuCl2(p-cym)(1,4-methylaminobenzene)] were resolved and the characterization was completed by spectroscopic UV–vis, FT-IR and 1H NMR studies. Electrochemical experiments were performed by cyclic voltammetry to estimate the redox potential of the Ru(II)/Ru(III) couple. The interaction with plasmid pBR322 DNA was studied through the examination of the electrophoretical mobility and atomic force microscopy, and interaction with ct-DNA by circular dichroism, viscosity measurements and fluorescence studies based on the DNA–ethidium bromide complex. The antiproliferative behavior of the series with L = methylpyridine was assayed against two tumor cell lines, i.e. LoVo and MiaPaca. The results revealed a moderate cytotoxicity with a higher activity for the LoVo cell line compared to the MiaPaca one.

New organometallic ruthenium(II) complexes with pyridine and toluene derivative ligands were prepared and characterized. Crystal structures were determined by X-ray diffraction. IC50 values for the compounds against LoVo and MiaPaca cell lines are in the range of micromolar amounts.Figure optionsDownload as PowerPoint slideHighlights
► In this work DNA interactions and anti-tumor assays of Ru(II) compounds are described.
► Crystal structures of three of them have been obtained by X-ray diffraction.
► Cyclic voltammetry studies reveal quasi-reversibility of the Ru(II)/Ru(III) pair.
► AFM, EM, CD, viscosity and fluorescence studies suggest interaction with DNA.
► Tests against MiaPaca and LoVo tumor cell lines revealed a moderate cytotoxicity.