Preparation, characterization, and photophysical study of thiazine dyes within the nanotubes and nanocavities of silicate host: influence of titanium dioxide nanoparticle on the protonation and aggregation of dyes

The photophysical properties of thionine and methylene blue have been investigated in the absence and presence of titanium dioxide nanoparticles encapsulated into the different nanoporous silicate materials: zeolite-Y, ZSM-5, and MCM-41. The titanium dioxide loaded zeolite samples were prepared by the ion-exchange method and the formation of TiO2 nanoparticles into the zeolite host materials was ascertained by UV-visible diffuse reflectance spectroscopy and ICP-OES measurement. The crystallinity of the silicate host was found to be intact as characterized by powder X-ray diffraction, nitrogen adsorption and desorption isotherm studies and TEM. The encapsulation of TiO2 into the zeolite host leads to the protonation of the dyes, indicating that the acidity of channels increased significantly in the presence of titanium dioxide in the zeolite host. In the case of zeolite-Y, with increasing loading of titanium dioxide nanoparticles, the aggregation of dyes is found to decrease. The absorption and emission spectra of the dyes, thionine and methylene blue, encapsulated into the nanochannel of ZSM-5 show a shift as compared to the spectra of the dyes in aqueous solution indicating that the planarity of the dye was perturbed due to the confinement effect of the nanochannels. ZSM-5 host with encapsulated titanium dioxide nanoparticles shows an increase in the fluorescence intensity of thionine present in the channels that is attributed to the presence of the dye in hydrophobic channels of the ZSM-5 host. The influence of the hydrophobic environment of the host on dye in the excited state was investigated by the pico- and femtosecond time-resolved spectral studies. The N-methyl-substituted analogue of thionine, methylene blue shows a different behavior due to the bulky nature of the dye. The aggregation of methylene blue in the cavities of zeolite-Y is less prevalent and the isomeric forms of the dye are not observed in this case in the excited state of the dye in the host channel

Effect of N(4)-Phenyl Substitution in 2-Oxo-1,2-dihydroquinoline-3-carbaldehyde Semicarbazones on the Structure, DNA/Protein Interaction, and Antioxidative and Cytotoxic Activity of Cu(II) Complexes

A new ligand, 2-oxo-1,2-dihydroquinoline-3-carbaldehyde semicarbazone (OQsc-H) (<b>1</b>);, its N(4)-phenyl derivative (OQsc-Ph) (<b>2</b>); and their corresponding copper­(II) complexes [CuCl₂(OQsc-H)]·H₂O·CH₃OH (<b>3</b>), [CuCl₂(OQsc-Ph)­(H₂O)]·CH₃OH (<b>4</b>), and [CuNO₃(OQsc-Ph)­(H₂O)]­NO₃·H₂O·C₂H₅OH (<b>5</b>) have been synthesized and characterized by structural, analytical, and spectral methods, in order to investigate the influence of N(4)-phenyl substitution on structure and pharmacological properties. In all of the complexes, the ligands coordinated to the Cu­(II) ion in a neutral fashion via ONO donor atoms. The single-crystal X-ray structures of neutral complex (<b>3</b>) and cationic complex (<b>5</b>) exhibit a slightly distorted square-pyramidal structure, while neutral complex (<b>4</b>) revealed an octahedral structure. The interaction of the compounds with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that compounds <b>1</b>–<b>5</b> could interact with CT-DNA through intercalation. A gel electrophoresis pictogram demonstrated the ability of the complexes (<b>3</b>–<b>5</b>) to cleave the pBR322 plasmid DNA through a hydrolytic process. The interactions of the compounds with bovine serum albumin (BSA) were also investigated using UV–visible, fluorescence, and synchronous fluorescence spectroscopic methods. The results indicated that all of the compounds could quench the intrinsic fluorescence of BSA in a static quenching process. Investigations of antioxidative properties showed that all of the compounds have strong radical scavenging potencies against hydroxyl radicals, 2,2-diphenyl-1-picrylhydrazyl radicals, nitric oxide, and superoxide anion radicals. Further, the cytotoxic effect of the compounds examined on cancerous cell lines such as human cervical cancer cells (HeLa), human laryngeal epithelial carcinoma cells (HEp-2), human liver carcinoma cells (Hep G2), human skin cancer cells (A431), and noncancerous NIH 3T3 mouse embryonic fibroblasts cell lines showed that all three complexes exhibited substantial cytotoxic activity. Further, all of the pharmacological investigations support the fact that there exists a strong influence of N(4)-phenyl substitution in semicarbazone

Evaluation of DNA binding, antioxidant and cytotoxic activity of mononuclear Co(III) complexes of 2-oxo-1,2-dihydrobenzoh]quinoline-3-carbaldehyde thiosemicarbazones

Four new 2-oxo-1,2-dihydrobenzoh]quinoline-3-carbaldehyde N-substituted thiosemicarbazone ligands (H-2-LR, where R = H, Me, Et or Ph) and their corresponding new cobalt(III) complexes have been synthesized and characterized. The structures of the complexes 2 and 3 were determined by single crystal X-ray diffraction analysis. The interactions of the new complexes with DNA were investigated by absorption, emission and viscosity studies which indicated that the complexes bind to DNA via intercalation. Antioxidant studies of the new complexes showed that the significant antioxidant activity against DPPH radical. In addition, the in vitro cytotoxicity of complexes 1-4 against A549 cell line was assayed which showed higher cytotoxic activity with lower IC50 values indicating their efficiency in killing the cancer cells even at very low concentrations. (C) 2012 Elsevier Masson SAS. All rights reserved