Copper(II) complex intercalated graphene oxide nanocomposites as versatile,reusable catalysts for click reaction

In this work, we report the efficient, high stable copper(II) complexes intercalated graphene oxide (GO) used as green catalysts for copper(II) complex mediated click reaction. Copper(II) Bis(2,2′-bipyridine) [Cu^II (bpy)₂] (C1) and Copper(II) Bis(1,10-phenanthroline) [Cu^II (phen)₂] (C2) have synthesized for the intercalation of corresponding nanocomposites with GO, [GO@Cu^II (bpy)₂] (GO-C1) and [GO@Cu^II (phen)₂] (GO-C2). The noncovalent interaction of complexes supported on the surface of the GO nanosheets proves as an evident active site to facilitate the enhanced catalytic activity of copper-catalyzed alkyne azide cycloaddition (Cu^IIAAC) reaction for the isolation of 1,4-disubstituted-1,2,3-triazoles as click products in shorter reaction time with 80%–91% yield (five examples). The X-ray diffraction (XRD) pattern of these composites shows the enhanced interlayers d-spacing range of 1.01–1.12 nm due to the intercalation of copper(II) complexes in between the GO basal planes and characterized by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), Raman, UV, scanning electron microscope (SEM), and thermogravimetric analysis (TGA). The as-prepared nanocomposites were employed for the typical click reactions using the substrates of azide and acetylene. These classes of composite materials can be referred to recyclable, heterogeneous, green catalysts with high atom economy and could also be used for the isolation of click products in biomolecules.     

Chemical Detoxification of Organomercurials

Organomercurials including methylmercury are ubiquitous environmental pollutants and highly toxic to humans. Now it could be shown that N‐methylimidazole based thiones/selones having an N‐CH₂CH₂OH substituent are remarkably effective in detoxifying various organomercurials to produce less toxic HgE (E=S, Se) nanoparticles. Compounds lacking the N‐CH₂CH₂OH substituent failed to produce HgE nanoparticles upon treatment with organomercurials, suggesting that this moiety plays a crucial role in the detoxification by facilitating the desulfurization and deselenization processes. This novel way of detoxifying organomercurials may lead to the discovery of new compounds to treat patients suffering from methylmercury poisoning.     

The Resting Oxidized State of Small Laccase Analyzed with Paramagnetic NMR Spectroscopy

The enzyme laccase catalyzes the reduction of dioxygen to water at the trinuclear copper center (TNC). The TNC comprises a type-3 (T3) and a type-2 (T2) copper site. The paramagnetic NMR spectrum of the small laccase from Streptomyces coelicolor (SLAC) without the substrate shows a mixture of two catalytic states, the resting oxidized (RO) state and the native intermediate (NI) state. An analysis of the resonances of the RO state is reported. In this state, hydrogen resonances only of the T3 copper ligands can be found, in the region of 12–22 ppm. Signals from all six histidine ligands are found and can be attributed to Hδ1, Hβ or backbone amide H^N nuclei. Two sequence-specific assignments are proposed on the basis of a second-coordination shell variant that also lacks the copper ion at the T1 site, SLAC−T1D/Q291E. This double mutant is found to be exclusively in the RO state, revealing a subtle balance between the RO and the NI states.     

Performance of 2-Hydroxy-1-Naphthaldehyde-2-Amino Thiazole as a Highly Selective Turn-on Fluorescent Chemosensor for Al(III) Ions Detection and Biological Applications

Journal of Fluorescence - The thiazole based Schiff base 2-hydroxy-1-naphthaldehyde-2-amino thiazole (receptor1) was synthesized through a single step process and characterized by spectroscopic and...     

An integrated strategy for in vivo metabolite profiling using high-resolution mass spectrometry based data processing techniques

An ongoing challenge of drug metabolite profiling is to detect and identify unknown or low-level metabolites in complex biological matrices. Here we present a generic strategy for metabolite detection using multiple accurate-mass-based data processing tools via the analysis of rat samples of two model drug candidates, AZD6280 and AZ12488024. First, the function of isotopic pattern recognition was proved to be highly effective in the detection of metabolites derived from [¹⁴C]-AZD6280 that possesses a distinct isotopic pattern. The metabolites revealed using this approach were in excellent qualitative correlation to those observed in radiochromatograms. Second, the effectiveness of accurate mass based untargeted data mining tools such as background subtraction, mass defect filtering, or a data mining package (MZmine) used for metabolomic analysis in detection of metabolites of [¹⁴C]-AZ12488024 in rat urine, feces, bile and plasma samples was examined and a total of 33 metabolites of AZ12488024 were detected. Among them, at least 16 metabolites were only detected by the aid of the data mining packages and not via radiochromatograms. New metabolic pathways such as S-oxidation and thiomethylation reactions occurring on the thiazole ring were proposed based on the processed data. The results of these experiments also demonstrated that accurate mass-based mass defect filtering (MDF) and data mining techniques used in metabolomics are complementary and can be valuable tools for delineating low-level metabolites in complex matrices. Furthermore, the application of distinct multiple data-mining algorithms in parallel, or in tandem, can be effective for rapidly profiling in vivo drug metabolites.     

Electron spin density distribution in the special pair triplet of Rhodobacter sphaeroides R26 revealed by magnetic field dependence of the solid-state photo-CIDNP effect

Photo-CIDNP (photochemically induced dynamic nuclear polarization) can be observed in frozen and quinone-blocked photosynthetic reaction centers (RCs) as modification of magic-angle spinning (MAS) NMR signal intensity under illumination. Studying the carotenoidless mutant strain R26 of Rhodobacter sphaeroides, we demonstrate by experiment and theory that contributions to the nuclear spin polarization from the three-spin mixing and differential decay mechanism can be separated from polarization generated by the radical pair mechanism, which is partially maintained due to differential relaxation (DR) in the singlet and triplet branch. At a magnetic field of 1.4 T, the latter contribution leads to dramatic signal enhancement of about 80,000 and dominates over the two other mechanisms. The DR mechanism encodes information on the spin density distribution in the donor triplet state. Relative peak intensities in the photo-CIDNP spectra provide a critical test for triplet spin densities computed for different model chemistries and conformations. The unpaired electrons are distributed almost evenly over the two moieties of the special pair of bacteriochlorophylls, with only slight excess in the L branch.     

Investigation of various synthetic protocols for self-assembled nanomaterials and their role in catalysis: progress and perspectives

Self-assembly is one of the most used strategies in the controlled synthesis and design of well-organized nanomaterials for various applications in diverse realms namely catalysis, sensors, microelectronics, energy storage, and energy conversion. It is quite common to see reports on the synthesis and design of several self-assembled nanomaterials for the application in the catalysis of various chemical, photochemical, and electrochemical reactions and processes. Nevertheless, a combined overview on the synthetic strategies for self-assembled nanomaterials has not been reported in any form in literature. Owing to the current interest shown and the future significance on the self-assembled nanomaterials, it is highly essential to have such an elaborated review on the progress and perspectives of synthesis of self-assembled nanomaterials and their subsequent application to catalysis of various chemical, photochemical, and electrochemical reactions and processes. In this review, we have highlighted various synthetic methodologies used so far for fabricating the self-assembled nanomaterials that includes Langmuir–Blodgett method, layer-by-layer assembly, amphiphilic (artificial and bio) self-assembly, and template-free approach. Nanomaterials derived from the above mentioned methods in various catalysis reactions are also highlighted in detail with an emphasis on confronts and prospects in the field of materials self-assembling and its concomitant application to catalysis.