Carbonyl–heterobimetallic Ru(II)/Fe(II)–complexes containing polypyridyl ligands: Synthesis, characterization, cellular viability assays and interactions with biomolecules

Abstract

This paper describes on the interaction studies of carbonyl heterobimetallic compounds of Ru(II)/Fe(II) containing polypyridyl ligands, with general formula ct–[RuCl(CO)(N–N)(dppf)]PF6, N–N = 1,10–phenanthroline (phen) 5; dipyrido[3,2–f:2′,3′–h]quinoxaline (dpq) 6; dipyrido[3,2–a:2′,3′–c]phenazine (dppz) 7; dipyrido[3,2–f:2′,3′–h]quinoxalino[2,3–b]quinoxaline (dpqQX) 8 and dppf = 1,1‘–bis(diphenylphosphino) ferrocene], with calf thymus DNA (ct–DNA) and bovine serum albumin (BSA). Also, it describes the cellular viability assays of these complexes in tumorigenic and non-tumorigenic cell lines. The carbonyl complexes 5–8 and their respective precursors with formula cis–[RuCl2(N–N)(dppf)], N–N = phen (1), dpq (2), dppz (3) and dpqQX (4), were characterized by elemental analysis and spectroscopic techniques (FTIR, UV–vis, 1H and 31P{1H} NMR). Also, a cyclic voltammetry study was performed for all complexes. The crystal structure of the complex 3 is presented and discussed. Spectrofluorimetric titrations shows spontaneous and strong interaction of 5–8 with BSA, through a static quenching mechanism, resulting in binding constants in the order of 104–106 L mol−1, at 310 K. Viscosity measurements and circular dichroism spectra prompts interactions of 5–8 with ct–DNA via non–classical intercalations or by an electrostatic pathway. MTT assays in breast tumor cells MDA–MB–231 and in non-tumorigenic cells MCF-10A and V79–4 cell lines revealed IC50 values ranging from 0.19 to 1.11 μmol L−1, 1.07–3.18 μmol L−1 and 1.29–3.85 μmol L−1 respectively, for complexes 5–8.