Phenylalanine-Tethered pH-Responsive Poly(2-Hydroxyethyl Methacrylate)

A series of pH-responsive random copolymers comprised of 2-hydroxyethyl methacrylate (HEMA) and tert-butyl carbamate (Boc)-protected phenylalanine methacryloyloxyethyl ester (Boc-Phe-EMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in N,N′-dimethylformamide (DMF) at 70 °C. The synthesized copolymers were comprehensively characterized using a combination of techniques, including ¹H NMR, FT-IR spectroscopy and size exclusion chromatography (SEC). Reactivity of each monomers towards controlled radical polymerization was evaluated by determining the reactivity ratios by virtue of extended Kelen-Tüdös method at high conversions revealed the higher reactivity of non-modified HEMA (r_HEMA=1.03) in contrast to Boc-Phe-EMA (r_Boc-Phe-EMA=0.48). Furthermore, the expulsion of the Boc-groups resulted copolymers with ionizable pendant primary ammonium and hydroxyl groups. To understand the glass transition behaviours of homo- and co-polymers, differential scanning calorimetric (DSC) measurements were carried out. The effect of HEMA content on the pH-sensitivity of the copolymers in aqueous medium was investigated through turbidity measurements. Finally, the counteranion exchange from trifluoroacetate to chloride provided copolymers with enhanced water solubility and unaltered phase transition pH.     

Actinides selective extractants coated magnetite nanoparticles for analytical applications

N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and bis(2-ethylhexy)phosphoric acid (HDEHP) were coated on Fe₃O₄ nanoparticles under different chemical conditions. The TODGA-coated magnetite nanoparticles (Fe₃O₄@TODGA) captured representative actinides Am(III) and Pu(IV) at 3–4 M HNO₃ with high efficiency. However, the HNO₃ induced pre-organization of TODGA, before coating on the magnetite nanoparticles, was found to be important for the sorption of Am(III) and Pu(IV) ions. The Fe₃O₄@HDEHP particles exhibited selectivity toward Pu(IV), and Am(III) did not sorb from 3 to 4 M HNO₃. The quantification of Pu(IV) preconcentrated on coated particles was carried out by removing the extractant coating in dioxane based scintillator, followed by liquid scintillation counting.

     

Graviton plus vector boson production to NLO in QCD at the LHC

We present the next-to-leading order QCD corrections to the associated production of the vector gauge boson (Z/W^±$Z/W^{\pm }$) and the graviton in the large extra dimension model at the LHC. We estimate the impact of the QCD corrections on the total cross sections as well as the differential distributions of the gauge bosons and find that they are significant. We also study the dependence of the cross sections on the arbitrary factorization scale and show the reduction in the scale uncertainties at NLO level. Further, we discuss the ultraviolet sensitivity of the theoretical predictions.     

Fluorescence quenching of CdS quantum dots by 4-azetidinyl-7-nitrobenz-2-oxa-1,3-diazole: a mechanistic study

Fluorescence quenching of CdS quantum dots (QDs) by 4‐azetidinyl‐7‐nitrobenz‐2‐oxa‐1,3‐diazole (NBD), where the two quenching partners satisfy the spectral overlap criterion necessary for Förster resonance energy transfer (FRET), is studied by steady‐state and time‐resolved fluorescence techniques. The fluorescence quenching of the QDs is accompanied by an enhancement of the acceptor fluorescence and a reduction of the average fluorescence lifetime of the donor. Even though these observations are suggestive of a dynamic energy transfer process, it is shown that the quenching actually proceeds through a static interaction between the quenching partners and is probably mediated by charge‐transfer interactions. The bimolecular quenching rate constant estimated from the Stern–Volmer plot of the fluorescence intensities, is found to be exceptionally high and unrealistic for the dynamic quenching process. Hence, a kinetic model is employed for the estimation of actual quencher/QD ratio dependent exciton quenching rate constants of the fluorescence quenching of CdS by NBD. The present results point to the need for a deeper analysis of the experimental quenching data to avoid erroneous conclusions.     

Hydrogen storage properties and neutron scattering studies of Mg2(dobdc)--a metal-organic framework with open Mg2+ adsorption sites

The hydrogen storage properties of Mg(2)(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate), a metal-organic framework possessing hexagonal one-dimensional channels decorated with unsaturated Mg(2+) coordination sites, have been examined through low- and high-pressure adsorption experiments, infrared spectroscopy, and neutron scattering studies.     

Synthesis, spectral characterization, thermal and photoluminescence properties of Zn(II) and Cd(II)-azido/thiocyanato complexes with thiazolylazo dye and 1,2-bis(diphenylphoshino)ethane

A series of complexes of the type [M(L)(dppe)X2]; where M=Zn(II) or Cd(II); L=4-(2'-thiazolylazo)chlorobenzene (L1), 4-(2'-thiazolylazo)bromobenzene (L2) and 4-(2'-thiazolylazo) iodobenzene (L3); dppe=1,2-bis(diphenylphosphino)ethane; X=N3- or NCS- have been prepared and characterized on the basis of their microanalysis, molar conductance, thermal, IR, UV-vis and 1H NMR spectral studies. IR spectra show that the ligand L is coordinated to the metal atom in bidentate manner via azo nitrogen and thiazole nitrogen. An octahedral structure is proposed for all the complexes. The thermal behavior of the complexes revealed that the thiocyanato complexes are thermally more stable than the azido complexes. All the complexes exhibit blue-green emission with high quantum yield as the result of the fluorescence from the intraligand emission excited state.     

Formal synthesis of (−)-stemoamide using a useful epimerization at C-8

The formal synthesis of (?)-stemoamide was achieved starting from l-pyroglutamic acid. The key steps used are the allylation using BF₃·OEt₂, ring closing metathesis, allylic oxidation and a novel epimerization at C8.     

Diversity-oriented approach to macrocyclic cyclophane derivatives by Suzuki-Miyaura cross-coupling and olefin metathesis as key steps

Palladium-catalyzed Suzuki-Miyaura (SM) cross-coupling reaction with allylboronic acid pinacol ester and titanium assisted cross-metathesis (CM)/ring-closing metathesis (RCM) cascade has been used to synthesize macrocyclic cyclophane derivatives.     

Hydride Pinning Pathway in the Hydrogenation of CO2 to Formic Acid on Dimeric Tin Dioxide

Capture of CO₂ and its conversion into organic feedstocks are increasingly needed as society moves towards a renewable energy economy. Here, a hydride-assisted selective reduction pathway is proposed for the conversion of CO₂ to formic acid (FA) over SnO₂ monomers and dimers. Our density functional theory calculations infer a strong chemisorption of CO₂ on SnO₂ clusters forming a carbonate structure, whereas heterolytic cleavage of H₂ provides a new pathway for the selective reduction of CO₂ to formic acid at low overpotential. Among the two investigated pathways for reduction of CO₂ to HCOOH, the hydride pinning pathway is found promising with a unique selectivity for HCOOH. The negatively-charged hydride forms on the cluster during the dissociation of H₂ and facilitates the formation of a formate intermediate, which determines the selectivity for FA over the alternative CO and H₂ evolution reaction. It is confirmed that SnO₂ clusters exhibit a different catalytic behaviour from their surface equivalents, thus offering promise for future work investigating the reduction of CO₂ to FA via a hydride pinning pathway at low overpotential and CO₂ capturing.     

Synthesis,anti‐proliferative activity,SAR, and kinase inhibition studies of thiazol‐2‐yl‐ substituted sulfonamide derivatives

A series of novel thiazol‐2‐yl substituted‐1‐sulfonamide derivatives were synthesized from anilines. This involved the coupling of sulfonyl chlorides with thiazol amine to obtain the final compounds 7a – 7j and 8a – 8j . All synthesized compounds were screened for anticancer activity against MCF‐7, HeLa, A‐549, and Du‐145 cancer cell lines by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. Preliminary bioassay suggests that most of the compounds show anti‐proliferation to different degrees, with doxorubicin used as positive control. The synthesized compounds show IC₅₀ values in the range 2.74–8.17 μM in the different cell lines. The compounds 7d , 7e , 8a , 8d , and 8e were active compared to doxorubicin. The compounds having butyl and pantyl chains were more active than their lower and higher carbon chains and also their ring counterparts.