Non-covalent DNA binding and cytotoxicity of certain mixed-ligand ruthenium(II) complexes of 2,2'-dipyridylamine and diimines

A series of mixed ligand ruthenium(II) complexes [Ru(Hdpa)2(diimine)](ClO4)2, 1-5 where Hdpa is 2,2'-dipyridylamine and diimine is 1,10-phenanthroline (phen) and a modified/extended 1,10-phenanthroline such as, 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), 5-methyldipyrido[3,2-d:2',3'-f]quinoxaline (mdpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz) have been isolated and characterized by analytical and spectral methods. The complex [Ru(Hdpa)2(phen)](PF6)2 1 has been structurally characterized and the coordination geometry around Ru(II) in it is described as distorted octahedral. 1H NMR spectral data reveal that 1-5 should have a C2 symmetry lying on the diimine plane due to the rapid flapping of the coordinated Hdpa ligands. The interaction of the complexes with calf thymus (CT) DNA has been explored by using absorption and emission spectral and viscometry and electrochemical techniques and the mode of DNA binding of the complexes has been proposed. The DNA binding affinity of the complexes decreases with decrease in number of planar aromatic rings in the co-ligand supporting the intercalation of the diimine co-ligands in between the DNA base pairs. Circular dichroic spectral studies reveal that the complexes 3-5 exhibit induced circular dichroism upon binding to CT DNA. Interestingly, upon interaction with CT DNA all the complexes show an increase in anodic current in the cyclic voltammograms suggesting that they are involved in electrocatalytic guanine oxidation. Interestingly, of all the complexes, only 5 alters the DNA superhelicity upon binding with supercoiled pBR322 DNA, which is consistent with its higher DNA binding affinity. Further, the cytotoxicities of the complexes against human cervical epidermoid carcinoma cell line (ME180) have been examined. Interestingly, 5 exhibits a cytotoxicity against ME180 higher than other complexes with potency approximately 8 times more than cisplatin for 24 h incubation but 4 times lower than cisplatin for 48 h incubation.     

Development of Methane Decomposition Catalysts for CO<Subscript>x</Subscript> Free Hydrogen

Now-a-days, catalytic decomposition of methane (CDM) into hydrogen and carbon is a promising technique for production of fuel cell grade hydrogen. The Ni based catalysts seems promising particularly for the production of CO_x free H₂ by methane decomposition process. The CDM activity and longevity of the Ni based catalysts are mainly influenced by the amount of Ni and type of support material. In this paper the CDM activity results are correlated with NiO crystallite size, Ni metal surface area and acidity of the catalysts. In case of bimetallic catalysts addition of Cu to Ni catalysts lead to enhance the CDM activity at higher temperature thus resulting in the increased concentration of hydrogen in the outlet stream. Finally, some of the carbon-based catalysts are studied for methane decomposition activity at higher temperature. The surface changes over carbon catalysts with methane decomposition are studied using various characterization techniques.     

Caught in Action: Visualizing Dynamic Nanostructures Within Supramolecular Systems Chemistry

Supramolecular systems chemistry has been an area of active research to develop nanomaterials with life-like functions. Progress in systems chemistry relies on our ability to probe the nanostructure formation in solution. Often visualizing the dynamics of nanostructures which transform over time is a formidable challenge. This necessitates a paradigm shift from dry sample imaging towards solution-based techniques. We review the application of state-of-the-art techniques for real-time, in situ visualization of dynamic self-assembly processes. We present how solution-based techniques namely optical super-resolution microscopy, solution-state atomic force microscopy, liquid-phase transmission electron microscopy, molecular dynamics simulations and other emerging techniques are revolutionizing our understanding of active and adaptive nanomaterials with life-like functions. This Review provides the visualization toolbox and futuristic vision to tap the potential of dynamic nanomaterials.     

The effects of thermal treatment of ZnO–ZnCr<Subscript>2</Subscript>O<Subscript>4</Subscript> catalyst on the particle size and product selectivity in dehydrocyclization of crude glycerol and ethylenediamine

The ZnO–ZnCr₂O₄ (Zn–Cr–O) sample obtained by decomposition of Zn-Cr hydrotalcite precursor was subjected to the thermal treatment at different temperatures and the physico-chemical properties of the Zn–Cr–O system were compared with its catalytic behavior in dehydrocyclization of crude glycerol and ethylenediamine (EDA). Upon high temperature treatment of Zn–Cr–O the Cr⁶⁺ ions underwent autoreduction to form stable Cr³⁺ species and the particle size of both ZnO and ZnCr₂O₄ increased dramatically. Thermal effect did not influence the intermolecular cyclisation of EDA to form pyrazine. By contrast, an inversely proportional dependence was found between the rate of formation of 2-methylpyrazine and the particle size of Zn–Cr–O whereas the rate of 2-pyrazinylmethanol was directly proportional to the particle size.     

A Three‐Photon Active Organic Fluorophore for Deep Tissue Ratiometric Imaging of Intracellular Divalent Zinc

Deep tissue bioimaging with three‐photon (3P) excitation using near‐infrared (NIR) light in the second IR window (1.0–1.4 μm) could provide high resolution images with an improved signal‐to‐noise ratio. Herein, we report a photostable and nontoxic 3P excitable donor‐π‐acceptor system (GMP) having 3P cross‐section (σ₃) of 1.78×10^?80 cm⁶ s² photon^?2 and action cross‐section (σ₃η₃) of 2.31×10^?81 cm⁶ s² photon^?2, which provides ratiometric fluorescence response with divalent zinc ions in aqueous conditions. The probe signals the Zn²⁺ binding at 530 and 600 nm, respectively, upon 1150 nm excitation with enhanced σ₃ of 1.85×10^?80 cm⁶ s² photon^?2 and σ₃η₃ of 3.33×10^?81 cm⁶ s² photon^?2. The application of this probe is demonstrated for ratiometric 3P imaging of Zn²⁺ in vitro using HuH‐7 cell lines. Furthermore, the Zn²⁺ concentration in rat hippocampal slices was imaged at 1150 nm excitation after incubation with GMP, illustrating its potential as a 3P ratiometric probe for deep tissue Zn²⁺ ion imaging.     

The synthesis and reactivity of some indenyl and bis-indenyl ruthenium carbonyl complexes

The reaction of [Ru₃(CO)₁₂] (1), with indene in refluxing xylene affords [{(η⁵-C₉H₇)Ru(CO)₂}₂] (2), in high yield. An analogous reaction of 1 with 2-phenylindene affords the expected dinuclear complex [{(η⁵-C₉H₆Ph)Ru(CO)₂}₂] (5), and a heptaruthenium cluster [(C₉H₄Ph)Ru₇(μ-H)(μ-CO)₂(CO)₁₆] (6). The indenyl ligand in compound 6 exhibits a novel bonding mode in which the benzenoid ring is μ₄,η¹:η¹:η²:η² bound to the cluster. Refluxing 1 with bis-indenyl methane affords the dinuclear complex [Ru₂(CO)₄{μ-(η⁵-C₉H₆)₂CH₂}] (7), which reacts with iodine via Ru-Ru bond cleavage to give [Ru₂I₂(CO)₄{(η⁵-C₉H₆)₂CH₂}] (8).     

Ethoxylation of p-chloronitrobenzene using phase-transfer catalysts by ultrasound irradiation: a kinetic study

Ethoxy-4-nitrobenzene was synthesized by the reaction of 4-chloronitrobenzene with potassium ethoxide in a homogeneous system using benzyltriethylammonium chloride (QCl) as a phase-transfer catalyst at 50 degrees C under ultrasound irradiation conditions. The use of phase-transfer catalysts and ultrasound has been compared and demonstrated in this nucleophilic substitution reactions. The kinetics of the reaction depends on the effect of amount of catalyst, quaternary ammonium salts, agitation speed, amount of potassium hydroxide, amount of ethanol, temperature and the frequency of the ultrasound waves on the conversion of the reaction.     

Molecular Rare‐Earth‐Metal Hydrides in Non‐Cyclopentadienyl Environments

Molecular hydrides of the rare‐earth metals play an important role as homogeneous catalysts and as counterparts of solid‐state interstitial hydrides. Structurally well‐characterized non‐metallocene‐type hydride complexes allow the study of elementary reactions that occur at rare‐earth‐metal centers and of catalytic reactions involving bonds between rare‐earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available.     

Isolation,structural assignment and synthesis of (SE)-2-methyloctyl 3-(4-methoxyphenyl) propenoate from the marine soft coral Sarcophyton ehrenbergi

A new metabolite 1 has been isolated from the marine soft coral Sarcophyton ehrenbergi along with two known diterpenoids 2 and 3 and cholesterol 4. The structure of 1 was determined by means of detailed spectroscopic analysis and unambiguously confirmed to have the S configuration by the synthesis of both enantiomers using 4-benzyl-2-oxazolidinone auxiliaries. (S)- and (R)-1, 3 and some of the synthetic intermediates were evaluated for cytotoxic activity against human lung cancer (A549), prostate cancer (DU145), cervical cancer (HeLa) and breast cancer (MCF-7) cell lines in an in vitro bioassay.