EPR studies of the hydroperoxy radical in x-irradiated single crystals of BaCl2·2H2O

Electron paramagnetic resonance studies of X-irradiated single crystals of BaCl₂-2H₂O have been made at room temperature. Four resonance lines are observed which can be grouped into two hyperfine doublets. Angular variation studies were made in the crystallographic ab, bc and ac planes. There are two magnetically equivalent but physically inequivalent magnetic complexes in the crystal lattice which are mutually perpendicular to each other. The paramagnetic species is identified as the hydroperoxy radical and a detailed discussion is made at the end.     

Isolable C@Fe3O4 nanospheres supported cubical Pd nanoparticles as reusable catalysts for Stille and Mizoroki-Heck coupling reactions

Cubical Pd nanoparticles incorporated magnetic nanospheres (Pd cNPs/C@Fe₃O₄) are found to be efficient catalysts for Stille and Mizoroki-Heck coupling reactions. A variety of aryl halides, including chlorides, are converted to biaryls and diphenylethenes with excellent yield and high TON. This immobilization of Pd cNPs on the surface C@Fe₃O₄ results in structurally stable catalytic sites. The observed enhanced catalytic activity is attributed to the high density of low-coordinated Pd {1 0 0} atoms present at the surface of the Pd cNPs/C@Fe₃O₄ catalyst. The advantages of the proposed catalytic system are its heterogeneity, high stability, absence of any toxic ligands, gram scale applicability, magnetic separability and consequent reusability.     

Specific ion adsorption and short-range interactions at the air aqueous solution interface

We have investigated the surface composition of alkali-halide aqueous solutions using grazing incidence x-ray fluorescence. Using mixtures of salts as a means to enhance the short-range effects, small differences in concentration over a few angstrom could be resolved, with, for example I- or Br- > Cl-. In order to explain our data, we need to include an effective potential accounting for the short-range (A) solvent mediated couplings, responsible for specific effects together with dispersion forces. This attractive potential (few k{B}T for halides) leads to concentration profiles which are in good agreement with recent numerical simulations.     

Soot emission reduction in oxygenated co-flow jet flames

A computational study was performed for ethylene/air non-premixed laminar co-flow jet flames using an axisymmetric CFD code to explore the effect of oxygenation on PAH and soot emissions. Oxygenated flames were established using N₂ diluted fuel stream along with O₂ enriched air stream such that the stoichiometric mixture fraction (Ζ_st) is varied but the adiabatic flame temperature is not materially changed. Simulations were carried out using a spatially and temporally accurate algorithm with detailed chemistry and transport. A detailed kinetic model involving 111 species and 784 reactions and a fairly detailed soot model were incorporated into the code. Two different approaches, one with constant flame height and other with constant inlet velocity are comprehensively examined to bring out the effects of changes in flame structure and residence time on soot emissions with respect to Z_st. With increase in Ζ_st, a drastic reduction in the formation of soot precursors (acetylene and benzene) and thus in soot emissions are observed. In the present study, oxygenated flames with Ζ_st ≥ 0.424 are considered as blue flames or completely soot free. For various oxygenated flames a C/O ratio between 0.45 and 0.6 is found to be most favorable for soot formation.     

Synthesis,spectral characterization and antitumor activity of phenothiazine derivatives

Different types of phenothiazine derivatives were synthesized by reactions of 10-alkyl-10H-phenothiazine-3-carbaldehydes. Structures of the prepared compounds were confirmed through spectroscopic techniques such as IR, ¹H NMR, ¹³C NMR and mass spectroscopy. All the compounds were studied for their antitumor activities.     

Iodine-catalyzed ultrasound-assisted construction of pyridines and their glutamine synthetase molecular docking

Iodine-promoted facile protocol is designed for the production of pyridines at room temperature under ultrasound irradiation. Eleven pyridine derivatives in excellent yields (91–97%) are synthesized with 2 hr reaction time. Additional advantage of the proposed ultrasound-assisted eco-friendly, cost-effective protocol is easy separation of product, and our in silico studies show good binding affinity toward binding and made strong hydrogen interactions.     

Vanadium(V)-substituted Keggin-type heteropolyoxotungstophosphates as electron transfer and antimicrobial agents: oxidation of glutathione and sensitization of MRSA towards β-lactam antibiotics

Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates, [ \textPV^\textV \textW _{1 1} \textO _{4 0} ] ^{4 -} [ {\text{PV}}^{\text{V}} {\text{W}}_{ 1 1} {\text{O}}_{ 4 0} ]^{{ 4 { - }}} (HPA1) and [ \textPV^\textV \textV^\textV \textW _{1 0} \textO _{4 0} ] ^{5 -} [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} ]^{{ 5 { - }}} (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 °C in aqueous medium. One mole of HPA1 consumes one mole of GSH and the product is the one-electron reduced heteropoly blue, [ \textPV^\textIV \textW _{1 1} \textO ₄₀ ] ^5- [ {\text{PV}}^{\text{IV}} {\text{W}}_{ 1 1} {\text{O}}_{ 40} ]^{ 5- } . But in the GSH-HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two-electron reduced heteropoly blue [ \textPV^\textIV \textV^\textIV \textW ₁₀ \textO ₄₀ ] ^7- [ {\text{PV}}^{\text{IV}} {\text{V}}^{\text{IV}} {\text{W}}_{ 10} {\text{O}}_{ 40} ]^{ 7- } . Both reactions show overall third-order kinetics. At constant pH, the order with respect to both [HPA] species is one and order with respect to [GSH] is two. At constant [GSH], the rate shows inverse dependence on [H⁺], suggesting participation of the deprotonated thiol group of GSH in the reaction. A suitable mechanism has been proposed and a rate law for the title reaction is derived. The antimicrobial activities of HPA1, HPA2 and [ \textPV^\textV \textV^\textV \textV^\textV \textW ₉ \textO _{4 0} ] ^{6 -} [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 9} {\text{O}}_{ 4 0} ]^{{ 6 { - }}} (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards penicillin G.