Bifunctional coordination polymers as efficient catalysts for carbon dioxide conversion

The multidentate ligand H₂ L upon complexation with Zn (II) and Cd (II) provide a one‐dimensional polymeric networks. These coordination polymers (CPs) CP‐1 and CP‐2 containing Zn (II) and Cd (II) metals respectively are well characterized. The single crystal structural analysis confirms the formation of one‐dimensional coordination polymer with zigzag fashion in CP‐1 and ladder chain CP‐2 . Both the CPs are applied as catalysts to synthesize various cyclic carbonates from epoxides and carbon dioxide. The catalysts are giving better conversion under solvent‐free and additive‐free condition using 10 bar CO₂ and 100 °C as optimized pressure and temperature. The detailed kinetic experiments suggesting the first order kinetics, the energy of activation (Ea) is calculated for this catalytic conversion.     

Enantioselective LC‐ESI‐MS/MS determination of dropropizine enantiomers in rat plasma and application to a pharmacokinetic study

We developed and validated a simple, sensitive, selective and reliable LC–ESI‐MS/MS method for direct quantitation of dropropizine enantiomers namely levodropropizine (LDP) and dextrodropropizine (DDP) in rat plasma without the need for derivatization as per regulatory guidelines. Dropropizine enantiomers and carbamazepine (internal standard) were extracted from 50 μL rat plasma using ethyl acetate. LDP and DDP resolved with good baseline separation (R_s = 4.45) on a Chiralpak IG‐3 column. The mobile phase consisted of methanol with 0.05% diethylamine pumped at a flow rate of 0.5 mL/min. Detection and quantitation were done in multiple reaction monitoring mode following the transitions m/z 237 → 160 and 237 → 194 for dropropizine enantiomers and the internal standard, respectively, in the positive ionization mode. The proposed method provided accurate and reproducible results over the linearity range of 3.23–2022 ng/mL for each enantiomer. The intra‐ and inter‐day precisions were in the ranges of 3.38–13.6 and 5.11–13.8 for LDP and 4.19–11.8 and 8.89–10.1 for DDP. Both LDP and DDP were found to be stable under different stability conditions. The method was successfully used in a stereoselective pharmacokinetic study of dropropizine enantiomers in rats following oral administration of racemate dropropizine at 100 mg/kg. The pharmacokinetic results indicate that the disposition of dropropizine enantiomers is not stereoselective and chiral inversion does not occur in rats.     

Pyrene-Hydrazone-π···Hole Coupled Turn-on Fluorescent and Naked- Eye Colorimetric Sensor for Cyanide: Role of Homogeneous π-Hole Dispersion in Anion Selectivity

A pyrene based probe associated with π···hole – hydrazone as one of the recognizing elements is synthesized and its turn in to a selective colorimetric and turn-on fluorescent sensor, (L³) for cyanide anion. This chemo sensor show high selectivity towards cyanide anion through photo electron transfer (PET) mechanism. The binding strength and sensitivity of the chemo sensor L³ towards cyanide are found to be 2.0 X 10⁴, and 4.44 x 10^-4 respectively. We have compared this high selectivity of the receptor towards cyanide, with our previously reported receptors L¹ and L². The detailed UV-Vis, Emission, ¹H-NMR, IR spectroscopic and Molecular Electrostatic Potential (MEP) studies reveals that the homogeneous π···hole dispersion in the aromatic ring governing the selectivity of the receptor towards cyanide anion. Such a positive π···hole homogeneous dispersion is missing in the case of sensor L², instead we have polarized π···hole dispersion towards 2^nd and 4^th position of di-nitrophenyl chromophoric unit in L².

Graphical Abstract

     

Thermal,mechanical, and topographical evaluation of nonstoichiometric α-cyclodextrin/poly(ε-caprolactone) pseudorotaxane nucleated poly(ε-caprolactone) composite films

Three pseudorotaxanes (PpR) comprised of poly (ε-caprolactone) (PCL) and α-cyclodextrin (α-CD) with varying stoichiometric ratios were synthesized and characterized. Wide-angle X-ray diffraction (WAXD) and thermogravimetric (TGA) analyses provided conclusive evidence for complexation between the guest PCL and host α-CD. The as-synthesized and characterized PpRs were used at 10 and 20% concentrations as nucleants to promote the bulk PCL crystallization in composite films. Both WAXD and TGA provided evidence for intact PpR structures in the composite films. Isothermal differential scanning calorimetric (I-DSC) analyses, performed at various crystallization temperatures demonstrated significant differences in the crystallization patterns among the composite films. In addition, I-DSC analyses showed higher Avrami constant values (n) in the PpR-nucleated composite PCL films (n ~ 3), indicating 3-dimensional crystal growth. In the case of neat PCL films, however, lower n values indicated crystal growth in 1-dimensions or 2-dimensions. Moreover, atomic force microscopic analyses showed large crests and pits in PpR-nucleated PCL composites, with irregular morphologies leading to higher surface roughness. To the contrary, the crests and pits were much smaller in the neat PCL films, resulting in lower surface roughness values. Finally, mechanical testing revealed higher tensile strength for PpR-nucleated PCL composites films, demonstrating larger load bearing capabilities. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1529–1537     

Vanadium dodecylamino phosphate: A novel efficient catalyst for synthesis of polyhydroquinolines

A novel vanadium dodecylamino phosphate was synthesised by an instant reaction between phosphoric acid and vanadyl acetylacetonoate using dodecylamine as the structure-directing agent at ambient temperature. The physicochemical characteristics of the material were investigated by a variety of analytical techniques. XRD studies revealed the presence of vanadium phosphate and hydrated vanadium phosphate phases in the framework of the material. The catalytic application of this material toward in the synthesis of polyhydroquinolines via Hantzsch condensation was investigated at ambient temperature. This method affords high yields within short reaction times. The influence of various reaction parameters such as different solvents, catalyst dosage, effect of aldehydes, and reusability was studied and a plausible mechanism proposed.     

Novel preparation method of nanosilver doped sol gel TiO2 photocatalysts for dye pollutant degradation

In the present study, a novel method for the silver nanoparticle incorporation into TiO₂ sol is reported which provides efficient dispersion of inserted metal in the calcined gel. Glucose mediated metal nanoparticle synthesis eliminates the additional steps for the introduction of dopant over the support. Ag nanoparticle acts as competent trapping centers preventing the recombination of electron?Chole pairs. Thus, in spite of the low UV intensity present in the sunlight, considerable enhancement in the catalytic efficiency was observed for the degradation of dye pollutants over nanosilver loaded TiO₂. Transmission electron microscopic images display the well isolated nanoparticles of silver having uniform dimensions of less than 5?nm over the best system, 2?wt% nanosilver loaded TiO₂, which is accountable for its effectiveness as a photocatalyst. Anatase is found to be the photocatalytic active phase, as evident from the X-ray diffraction studies.     

An Efficient Process for the Synthesis of Renin Inhibitor,ABT-517

An efficient process for the preparation of renin inhibitor, ABT-517 is described. The process avoids solvent extractions or chromatographic purifications and is used on multi-kilogram scale.     

Towards Photochromic Azobenzene-Based Inhibitors for Tryptophan Synthase

Light regulation of drug molecules has gained growing interest in biochemical and pharmacological research in recent years. In addition, a serious need for novel molecular targets of antibiotics has emerged presently. Herein, the development of a photocontrollable, azobenzene-based antibiotic precursor towards tryptophan synthase (TS), an essential metabolic multienzyme complex in bacteria, is presented. The compound exhibited moderately strong inhibition of TS in its E configuration and five times lower inhibition strength in its Z configuration. A combination of biochemical, crystallographic, and computational analyses was used to characterize the inhibition mode of this compound. Remarkably, binding of the inhibitor to a hitherto-unconsidered cavity results in an unproductive conformation of TS leading to noncompetitive inhibition of tryptophan production. In conclusion, we created a promising lead compound for combatting bacterial diseases, which targets an essential metabolic enzyme, and whose inhibition strength can be controlled with light.     

Diamond kinoform hard X‐ray refractive lenses: design,nanofabrication and testing

Motivated by the anticipated advantageous performance of diamond kinoform refractive lenses for synchrotron X‐ray radiation studies, this report focuses on progress in designing, nanofabricating and testing of their focusing performance. The method involves using lift‐off and plasma etching to reproduce a planar definition of numerically determined kinoform refractive optics. Tests of the focusing action of a diamond kinoform refractive lens at the APS 8‐ID‐I beamline demonstrate angular control of the focal spot.     

Influence Of Zro2 on The Physicochemical Properties of Phosphate-Based Glasses and Glass Ceramics

Abstract

Phosphate-based bioactive glasses and their glass ceramics for 47P₂O₅– (30.5)CaO–(22.5 ? x)Na₂O–xZrO₂ for different ZrO₂ contents (x = 0, 1.5, 3.0, 4.5, and 6.0 mol%) were prepared through melt quenching and controlled heat treatment procedures. The amorphous nature of glasses and the presence of crystalline phases in glass ceramics were studied by means of X-ray diffraction (XRD) studies. The density, molar volume, ultrasonic velocities, attenuation, elastic constants, and microhardness of glass and glass ceramics were used to study the structural changes. The formation of hydroxyapatite layer on the surface of glasses and glass ceramics after immersion in simulated body fluid (SBF) was explored through XRD, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) analyses. The results indicate that the added ZrO₂ increases the crosslink density of glasses, resulting in network stability, and also induces the formation of an apatite layer on the surface of glasses.

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