Activation of hydrocarbons on acidic zeolites: superior selectivity of methylation of ethene with methanol to propene on weakly acidic catalysts

The study of methylation of ethene with methanol to propene over MFI zeolites with different heteroatoms has found that an efficient catalyst with weak acidities prevented the side reactions related with the formation of ethene oligomers from occurring, as evidenced by in situ IR spectroscopy, leading to superior propene selectivity in the product distribution.     

Elucidation of inhibitors in the dimerization of acrylonitrile using [RuCl2(DMSO)4/CH3CH2COONa/DMSO/o-benzoylbenzoic acid] as catalyst

A study of inhibitors in the dimerization of acrylonitrile using the novel catalytic system of [RuCl₂(DMSO)₄/CH₃CH₂COONa/DMSO/o-benzoylbenzoic acid] was carried out by examining the effect of reaction products on the catalytic activity. 1,4-Dicyanobuta-1,3-diene (3), one of the linear dimer products of acrylonitrile, inhibited the Ru-catalyzed reaction. Methylthiomethyl o-benzoylbenzoate (8), a by-product which was produced from carboxylic acid and DMSO under the reaction conditions, also acted as an inhibitor.     

Electronegative oligothiophenes for n-type semiconductors: difluoromethylene-bridged bithiophene and its oligomers

The synthesis of difluoromethylene-bridged bithiophene and its oligothiophenes are reported. The spectroscopic and electrochemical measurement as well as X-ray analyses unambiguously revealed that the difluoromethylene bridge largely contributes to keeping planarity between the thiophene rings and lowering the LUMO level. The perfluorohexyl-substituted quaterthiophene derivatives showed n-type semiconducting behavior with field-effect electron mobilities up to 0.018 cm2 V-1 s-1.     

Defects with deep levels induced by plastic deformation and electron irradiation in El2-free GaAs

Abstract

Defects with deep electronic energy levels induced by electron irradiation at room temperature or plastic deformation at 450°C in GaAs in which grown-in EL2 defects are previously eliminated by heat-treatment are investigated by means of measurements of the optical absorption and the Hall effect. Thermal stabilities of the induced defects are studied by tracing the changes mainly in the absorption specturm due to isochronal annealing. The absorptions both in deformed and irradiated specimens are mostly photo-unquenchable. Therefore, the defects induced by above two procedures are identified not to be EL2. Semi-insulating or n-type specimens convert to p-type by plastic deformation or electron irradiation, showing that high densities of acceptors are generated by the above two procedures.     

Studies on multiferroic materials in high magnetic fields

In this article, studies on the magnetoelectric effects of multiferroic materials in high magnetic fields, particularly pulsed magnetic fields, are discussed and results for some representative materials are presented. In the discussions on representative materials, the relationship between the crystallographic symmetry and the linear magnetoelectric effect in Cr₂O₃ is introduced. Then drastic changes in polarization caused by magnetic transitions are discussed through a case study of manganites with a perovskite-type structure. In addition, high field studies on the magnetoelectric effects in BiFeO₃, which is an exceptional multiferroic material, are presented and discussed in the framework of the Landau-Ginzburg theory.     

Electrostatic and electrochemical nature of liquid-gated electric-double-layer transistors based on oxide semiconductors

The electric-double-layer (EDL) formed at liquid/solid interfaces provides a broad and interdisciplinary attraction in terms of electrochemistry, photochemistry, catalysts, energy storage, and electronics because of the large interfacial capacitance coupling and its ability for high-density charge accumulation. Much effort has recently been devoted to the fundamental understanding and practical applications of such highly charged EDL interfaces. However, the intrinsic nature of the EDL charging, whether it is electrostatics or electrochemistry, and how to distinguish them are far from clear. Here, by combining electrical transport measurements with electrochemical impedance spectroscopy (EIS), we studied the charging mechanisms of highly charged EDL interfaces between an ionic liquid and oxide semiconductor, ZnO. The direct measure for mobile carriers from the Hall effect agreed well with that from the capacitance-voltage integration at 1 Hz, implying that the pseudocapacitance does not contribute to carrier transport at EDL interfaces. The temperature-frequency mapping of EIS was further demonstrated as a "phase diagram" to distinguish the electrostatic or electrochemical nature of such highly charged EDL interfaces with densities of up to 8 × 10(14) cm(-2), providing a guideline for electric-field-induced electronic phenomena and a simple method for distinguishing electrostatic and electrochemical charging in EDLTs not only based on a specific oxide semiconductor, ZnO, but also commonly applicable to all types of EDL interfaces with extremely high-density carrier accumulation.     

Atropisomeric lactam chemistry: catalytic enantioselective synthesis, application to asymmetric enolate chemistry and synthesis of key intermediates for NET inhibitors

In the presence of (R)-SEGPHOS-Pd(OAc)₂ catalyst, the intramolecular N-arylation of ortho-tert-butyl-NH-anilides possessing an iodophenyl group proceeded in a highly enantioselective manner (89-98% ee) to give optically active atropisomeric lactams having an N-C chiral axis. MPLC purification of the enantio-enriched lactam products using an achiral silica gel column led to a further increase in the enantiomeric purity (>99% ee). The reaction of the lithium enolate prepared from the optically active atropisomeric lactam with various alkyl halides gave α-substituted and α,α-disubstituted lactam products with high diastereoselectivity. α-Alkylated lactam derivatives were efficiently converted to key intermediates for the synthesis of an NET inhibitor.     

The effect of water-miscible organic solvents on the substitution reaction of Keggin-type heteropolysilicates and -germanates with vanadium(V) ion

The substitution reaction of Keggin-type polyoxometalates, [XM₁₂O₄₀]ⁿ⁻ (X = Si, Ge, P, or As; M = Mo or W), with vanadium(V) ion was investigated with cyclic voltammetry, Raman spectroscopy, and ³¹P NMR. The effect of organic solvents, such as acetonitrile (ACN), tetrahydrofuran (THF), formamide (FA), N-methylformamide (NMF), and N-methylacetoamide (NMA) on their substitution reactions was examined. In aqueous and aqueous-FA, -NMF, and -NMA solutions, the molybdenum or tungsten unit in the Keggin-anions was substituted with vanadium(V) ion to form V(V)-substituted polyoxometalates, while no substitution reaction occurred in aqueous-ACN and -THF solutions. It is suggested that this results from the relationship between the total anion charge and the permittivity of organic solvents.