Photophysical properties and in vitro cytotoxicity studies of new Ru(ii) carbonyl complexes and mixed geometrical Ru(ii)–Ni(ii) complex in HS-DNA/BSA protein and human lung (A549) and liver (HepG2) cells

Abstract

Two new ruthenium(II) carbonyl complexes have been synthesized from [RuHCl(CO)(PPh₃)₃] and 2-hydroxy-1-naphthaldehydethiosemicarbazone [H₂-(Nap-tsc)]. The stoichiometric reaction afforded two different complexes (1 and 2) exhibiting different structural motifs. In complex 1, the ligand coordinated through the N(2) nitrogen and thiolate sulphur by forming a strained four member chelate ring by leaving three donor sites (phenolic oxygen, N1 nitrogen and terminal nitrogen) uncoordinated. However, in complex 2, it coordinated as an ONS tridentate with the formation of a six member and a five member ring. In order to utilize the three unutilized donor sites in complex 1, it was reacted further with [NiCl₂(PPh₃)₂], which resulted in the formation of a new hetero bimetallic complex 3 wherein all the donor atoms of the ligand were utilized. The complexes have been characterized analytically and spectroscopically and X-ray diffraction (1, 3) and have also been evaluated for their binding affinity with HS-DNA. The electrostatic binding of the complexes with DNA was evident from absorption and fluorescence titration experiments. The binding interaction between the complexes 1–3 and bovine serum albumin (BSA) was studied by absorption, fluorescence and synchronous spectra at room temperature. From the results, it is inferred that complex 2 had a better binding ability with the tryptophan residues of BSA. The mechanism of complex interaction was found as static quenching. The in vitro cytotoxicity of metal complexes (1–3) has been evaluated by colorimetric assay (MTT assay).