High surface area V-Mo-N materials synthesized from amine intercalated foams

Nanocrystalline ternary V-Mo nitrides were prepared via nitridation of amine intercalated oxide foams or bulk ternary oxides. Specific surface areas were in the range between 40 and 198 m² g⁻¹ and strongly depended on the preparation method (foam or bulk oxide). Foamed precursors were favorable for vanadium rich materials, while for molybdenum rich samples bulk ternary oxides resulted in higher specific surface areas. The materials were characterized via nitrogen physisorption at 77 K, X-ray diffraction patterns, electron microscopy, and elemental analysis.     

High-pressure accelerated asymmetric organocatalytic Friedel-Crafts alkylation of indoles with enones: application to quaternary stereogenic centers construction

An organocatalytic Friedel-Crafts alkylation of indoles with α,β-unsaturated ketones was found to be efficiently accelerated under high-pressure conditions with a low loading of chiral primary amine salts with good yield and enantioselectivity up to 90%. This approach also allows, for the first time, selected indole derivatives containing quaternary stereogenic centers to be obtained from prochiral β,β-disubstituted enones with an enantioselectivity up to 80%.     

On unbounded composition operators in L^2-spaces

Fundamental properties of unbounded composition operators in \(L^2\) -spaces are studied. Characterizations of normal and quasinormal composition operators are provided. Formally normal composition operators are shown to be normal. Composition operators generating Stieltjes moment sequences are completely characterized. The unbounded counterparts of the celebrated Lambert’s characterizations of subnormality of bounded composition operators are shown to be false. Various illustrative examples are supplied.     

Photodissociation of singly protonated peptides at 193 nm investigated with tandem time-of-flight mass spectrometry

Photodissociation at 193 nm of some singly protonated peptides generated by matrix-assisted laser desorption/ionization was investigated using tandem time-of-flight mass spectrometry. For peptides with arginine at the C-terminus, x, upsilon, and w fragment ions were generated preferentially while a and d fragment ions dominated for peptides with arginine at the N-terminus. These are the same characteristics as photodissociation at 157 nm reported previously. Overall, the photodissociation spectra obtained at 157 and 193 nm were strikingly similar.     

Theoretical Raman and infrared spectra, and vibrational assignment for para-halogenoanilines: DFT study

The theoretical IR and Raman spectra of para-halogenoanilines, 4-XC(6)H(4)NH(2) (X=F, Cl and Br) were calculated by using the density functional B3LYP method with the 6-311++G(df,pd) basis set. The theoretical spectra show very good agreement with experiment. The rigorous normal coordinate analyses have been performed, and the detailed vibrational assignment has been made on the basis of the calculated potential energy distributions (PEDs). Several ambiguities and contradictions in the previously reported vibrational assignments have been clarified. The "marker bands" and the effects of the halogen substituent on the characteristic aniline bands in the IR and Raman spectra are discussed.     

A new strategy for asymmetric synthesis of aminophosphonic acid derivatives: the first enantioselective catalytic reduction of C-phosphorylated imines

The first highly enantioselective catalytic reduction of 1-imino-2,2,2-trifluoroethylphosphonates and the synthesis of enantiomerically enriched biorelevant phosphonotrifluoroalanine is reported.     

Simple determination of azasetron in rat plasma by column-switching high-performance liquid chromatography

For the quantification of azasetron in rat plasma samples, a column-switching HPLC method was developed and validated. Following dilution of plasma samples with mobile phase A (17?mM potassium phosphate buffer (pH 3.0)) and simple protein precipitation by addition of perchloric acid (60%), the mixture was directly injected onto the pre-column. After endogenous plasma substances were eluted to waste, the analyte was transferred to the trap column by switching the system. Then, the analyte was back-flushed to the analytical column for separation with mobile phase B (a 22:78 v/v mixture of acetonitrile and 17?mM potassium phosphate buffer (pH 3.0)) and detected at 250?nm using a photodiode array detector. A linear standard curve was obtained in the concentration range of 10-800?ng/mL with the correlation coefficient (r) of 0.9998. The intra- and inter-day precision and accuracy values for azasetron were in the ranges of 0.3-12.9% and 89.7-101.4%, respectively. The method was valid in terms of specificity, precision, and accuracy. In addition, this efficient analytical method was successfully applied to determine plasma concentrations of azasetron following oral administration of azasetron at a dose of 4.0?mg/kg to rats.     

A selective chromogenic chemosensor for carboxylate salt recognition

A new heteroditopic chromogenic chemosensor bearing a crown ether substituted at the intraannular position with a nitrophenylthiourea moiety has been synthesized. The binding behavior of this sensor was investigated by (1)H NMR spectroscopy and UV-vis spectroscopy. The receptor binds in a cooperative fashion to both a potassium cation and a carboxylate anion whereas a sodium cation sequesters an anion from the anion-receptor complex. The binding events are confirmed by selective color changes of the chemosensor solution.     

Penultimate unit effects in the free‐radical copolymerization of styrene with acrylonitrile according to theoretical thermochemistry

Penultimate unit effects in the free‐radical copolymerization of styrene with acrylonitrile were investigated by the consideration of the theoretical thermochemistry of three subsequent propagation steps in the copolymerization process at 298 K and the electronic properties of the relevant reactants. The total energies, zero‐point energies incorporating a 0.96 scale factor, and thermal enthalpy corrections for all optimized structures were computed with the B3LYP density functional theory and the 6‐311G(d,p) basis set. The penultimate unit effect on the enthalpy of reaction for elementary propagation reactions ranged from ?1.2 to 2.7 kcal/mol. The enthalpies of elementary copolymerization propagation reactions showed that penultimate unit effects depended not only on the γ substituent itself but also on the terminal unit of the growing radical and the monomer being attached. The exothermicity of the addition of radicals, varying in the penultimate unit for a given monomer, was lower for more polar radicals and smaller Mulliken charges at the radical atom, except for radicals with a CN substituent placed in the γ position when they reacted with acrylonitrile. For the latter system, the repulsive interactions between the CN substituent and nitrile group of the monomer being added contributed to the reaction enthalpy. Almost no penultimate unit effect was detected upon spin distribution at the radical atom, and this probably indicated the absence of the independent implicit penultimate model. The results obtained strengthen the concept of the inseparability of implicit and explicit penultimate unit effects in radical copolymerization. However, it appears that for the styrene–acrylonitrile copolymerization system, the explicit penultimate model prevails over the implicit penultimate model. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3592–3603, 2002