Synthesis, characterization, photophysical, lipophilicity, and in vitro fluorescence studies of mono-, di-, and trinuclear Ru(II) polypyridyl complexes of pyridinyl benzimidazole derivatives.

The synthesis, characterization, and photophysical properties of mononuclear ruthenium(II) complexes [Ru(bpy)2(py-BIm-Bz)](ClO4)2 (1) and [Ru(phen)2(py-BIm-Bz)](ClO4)2 (2), dinuclear complexes [(bpy)2Ru-µ2-(py-BIm-Xy)-Ru(bpy)2](ClO4)4 (3) and [(phen)2Ru-µ2-(py-BIm-Xy)-Ru(phen)2](ClO4)4 (4), and trinuclear complexes [((bpy)2Ru)3-µ3-(py-BIm-Ms)](ClO4)6 (5) and [((phen)2Ru)3-µ3-(py-BIm-Ms)](ClO4)6 (6) of pyridinyl benzimidazole ligands with 2,2'-bipyridine or 1,10-phenanthroline ancillary ligands as fluorescent imaging probes are reported. The ligand py-BIm-Bz crystallizes with inherent disorder due to the competing π-π interactions between two (2-pyridinyl)benzimidazole moieties aligned in parallel and in the opposite direction. The complex 2 forms non-merohedrally twinned crystal with the twin law matrix [0.259 -0.776 0.741, 0.000 -1.000 0.000, 1.259 -0.776 -0.259] and a batch scale factor (BASF) of 0.05. The electronic absorption spectra of the complexes 1-6 differ typically in the π-π* transitions of the ancillary ligands. The complexes exhibit orange-red fluorescence at 624-634 nm at room temperature with quantum yield (0.096 - 0.117) higher than that of [Ru(bpy)3]2+ and a hypsochromic shift of the emission maxima in frozen acetonitrile (λem = 613-628 nm) due to the rigidochromic effect. The excited state lifetime of these complexes are in the range 72-194 ns with the mononuclear complexes exhibiting the highest values. The complexes 1-6 are nontoxic (IC50 > 275 µM) toward both HeLa and Vero cell lines. They are hydrophilic and the logPo/w values are in the -0.53 to -1.46 range. The confocal microscopic study of cellular localization of the complexes on the HeLa cells co-stained with the nuclear staining DAPI dye shows their localization in the cytoplasm and the nuclear membrane penetration increases with nuclearity.

Dinuclear platinum(II) complexes of imidazophenanthroline-based bridging ligands as potential anticancer agents: synthesis, characterization, and in vitro cytotoxicity studies.

The synthesis and characterization of the dinucleating ligands 1,2-bis(2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenoxy)ethane (L1) and 1,2-bis(2-(1H-imidazo[4,5-f][1, 10]phenanthrolin-2-yl)phenoxy)hexane (L2) and their dinuclear complexes [Pt2(L1)Cl4] (1) and [Pt2(L2)Cl4] (2) and the in vitro cytotoxicity of the complexes against HeLa, HepG2, and MCF-7 cell lines are reported. Ligand L1 crystallizes in the orthorhombic system with the space group Pbca. The complexes 1 and 2 undergo aquation following first-order kinetics. The MTT and trypan blue assays indicate higher cytotoxicity of the complexes towards the HepG2 and MCF-7 cell lines compared to cisplatin. The AO/EB assay and flow cytometry by Annexin V alexa fluor®488/PI double staining assay demonstrate distinct morphological changes of apoptosis in a dose dependent manner. The cell cycle analysis shows a marked decrease in the DNA content in the G0/G1 phase with an increase in the G2/M phase on increasing the concentration of the complexes. The potential of the complexes as anticancer agents is demonstrated by their antiproliferative activity on the cell lines. The complexes interact with the major groove of DNA through H-bonding between the imidazole N-H protons and the nucleotide residues DC`21/N4 (cytosine) for complex 1 and DT`7/O2 (thymine) and DT`19/O2 (thymine) for complex 2, with the binding energy of - 1.98 and - 4.45 kcal/mol, respectively. Dinuclear Pt(II) complexes of imidazophenanthroline-based dinucleating ligands exhibit antiproliferative activity against HeLa, HepG2, and MCF-7 cell lines.