Titas Mukherjee

Synthesis, characterization, crystal structure, and DNA-binding of ruthenium(II) complexes of heterocyclic nitrogen ligands resulting from a benzimidazole-based quinazoline derivative

The reaction of cis-[RuCl2(dmso)4] with [6-(2-pyridinyl)-5,6-dihydrobenzimidazo[1,2-c]quinazoline] (L) afforded in pure form a blue ruthenium(II) complex, [Ru(L1)2] (1), where the original L changed to [2-(1H-benzoimidazol-2-yl)-phenyl]-pyridin-2-ylmethylene-amine (HL1 ). Treatment of RuCl3 · 3H2O with L in dry tetrahydrofuran in inert atmosphere led to a green ruthenium(II) complex, trans-[RuCl2(L2)2] (2), where L was oxidized in situ to the neutral species 6-pyridin-yl-benzo[4,5]imidazo[1,2-c]quinazoline (L2 ). Complex 2 was also obtained from the reaction of RuCl3 · 3H2O with L2 in dry ethanol. Complexes 1 and 2 have been characterized by physico-chemical and spectroscopic tools, and 1 has been structurally characterized by single-crystal X-ray crystallography. The electrochemical behavior of the complexes shows the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The interaction of these complexes with calf thymus DNA by using absorption and emission spectral studies allowed determination of the binding constant K b and the linear Stern–Volmer quenching constant K SV.

Ruthenium(II) complexes of pyrrol-azo ligands: cytotoxicity, interaction with calf thymus DNA and bovine serum albumin

Two ruthenium(II) complexes of newly designed pyrrol-azo ligands(L) and bipyridine(bpy) formulated as [Ru(L)(bpy)2]ClO4, where HL1 = (4-chloro-phenyl)-(1H-pyrrol-2-yl)-diazene (1) complex 1 and HL2 = (4-nitro-phenyl)-(1H-pyrrol-2-yl)-diazene for 2, were isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods. The electrochemical behavior of the complexes showed the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The study of cytotoxicity effects of 1 and 2 on human breast cancer cells (MCF 7, MDA-MB 231) and cervical cancer cell (HeLa) taking Cisplatin as a positive reference showed that 1 exhibited higher cytotoxicity against cancer cell lines than 2, but less activity than Cisplatin. The interaction of 1 with calf thymus DNA (CT-DNA) using absorption, emission spectral studies, viscosity-measurement, and electrochemical techniques has been used to determine the binding constant K b and the linear Stern–Volmer quenching constant K SV. The results indicate that 1 strongly interacts with CT-DNA in groove binding mode. The interaction of bovine serum albumin (BSA) with 1 was also investigated with the help of spectroscopic tools. Absorption spectroscopy proved the formation of a BSA-[Ru(L1)(bpy)2]ClO4 complex.

Synthesis, characterization, interactions with DNA and bovine serum albumin (BSA), and antibacterial activity of cyclometalated iridium(III) complexes containing dithiocarbamate derivatives

Three mononuclear cyclometalated iridium(III) complexes having dithiocarbamate ligands, [IrIII(2-C6H4py)2(L)] (where 2-C6H4py = 2-phenylpyridine; and L1H = 4-MePipzcdtH, L2H = MorphcdtH, and L3H = 4-BzPipercdtH for 1, 2, and 3, respectively), were synthesized from [Ir(2-C6H4py)2Cl]2·1/4CH2Cl2 by displacing the two bridging chlorides with one dithiocarbamate ligand. The complexes were characterized using physicochemical and spectroscopic tools along with structural analysis of [Ir(2-C6H4py)2(L2)] (2) by single crystal X-ray diffraction. Structural analysis of 2 showed a distorted octahedron in which the nitrogen donor of one 2-phenylpyridine and the carbon donor of another 2-phenylpyridine are in axial positions, trans to one another. Electrochemical analysis by cyclic voltammetry showed the irreversible two-electron equivalent reduction voltammograms of 1, 2, and 3 attributable to Ir(III) to Ir(I). Electronic characterizations of these complexes are consistent with significant delocalization of the sulfur electron density onto the empty metal d-orbital. The intercalative interaction of the complexes with calf thymus DNA was evaluated using absorption, fluorescence quenching, and viscosity measurements. The binding affinities of these complexes with bovine serum albumin were estimated in terms of quenching constants using the Stern–Volmer equation. Study of antibacterial activities of the complexes by agar disk diffusion against some species of pathogenic bacteria was also performed. Graphical Abstract