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Hokkaido University Collection of Scholarly and Academic Papers (136.069 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

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Mostrando recursos 41 - 60 de 171

  1. Amidation of Carboxylic Acids with Amines by Nb2O5 as a Reusable Lewis Acid Catalyst

    Ali, Md. A.; Siddiki, S. M. A. H.; Onodera, Wataru; Kon, Kenichi; Shimizu, Ken-ichi
    Among 28 types of heterogeneous and homogenous catalysts tested, Nb2O5 shows the highest yield for direct amidation of n-dodecanoic acid with a less reactive amine (aniline). The catalytic amidation by Nb2O5 is applicable to a wide range of carboxylic acids and amines with various functional groups, and the catalyst is reusable. A comparison of the results of the catalytic study and an infrared study of the acetic acid adsorbed on the catalyst suggests that activation of the carbonyl group of the carboxylic acid by Lewis acid sites on Nb2O5 is responsible for the high activity of the Nb2O5 catalyst. Kinetic...

  2. Platinum-catalyzed reduction of amides with hydrosilanes bearing dual Si-H groups: a theoretical study of the reaction mechanism

    Nakatani, Naoki; Hasegawa, Jun-ya; Sunada, Yusuke; Nagashima, Hideo
    A platinum-catalyzed amide reduction through hydrosilylation with 1,2-bis(dimethylsilyl) benzene (BDSB) was investigated on a theoretical basis. While the platinum-catalyzed hydrosilylation of alkenes is well known, that of carbonyl groups rarely occurs. The only exception involves the use of bifunctional hydrosilanes having dual, closely located Si-H groups, which accelerate the hydrosilylation of carbonyl groups, leading to successful reduction of amides to amines under mild conditions. In the present study, we determined through density functional theory calculations that the platinum-catalyzed hydrosilylation of the C=O bond proceeds via a Pt(IV)-disilyl-dihydride intermediate with an associated activation energy of 29.6 kcal mol(-1). Although it was...

  3. Ruthenium-Immobilized Periodic Mesoporous Organosilica: Synthesis, Characterization, and Catalytic Application for Selective Oxidation of Alkanes

    Ishito, Nobuhiro; Kobayashi, Hirokazu; Nakajima, Kiyotaka; Maegawa, Yoshifumi; Inagaki, Shinji; Hara, Kenji; Fukuoka, Atsushi
    Periodic mesoporous organosilica (PMO) is a unique material that has a crystal-like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl2(CO)(3)](2), is successfully immobilized onto 2,2'-bipyridine (BPy) units of PMO to form a single-site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru-immobilized PMO oxidizes the tertiary CH bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary CH bonds, thereby exhibiting remarkably high regioselectivity. Moreover, the catalyst converts cis-decalin to cis-9-decalol in a 63% yield with complete retention of the substrate stereochemistry. The Ru catalyst...

  4. Energy dissipative photoprotective mechanism of carotenoid spheroidene from the photoreaction center of purple bacteria Rhodobacter sphaeroides

    Arulmozhiraja, Sundaram; Nakatani, Naoki; Nakayama, Akira; Hasegawa, Jun-ya
    Carotenoid spheroidene (SPO) functions for photoprotection in the photosynthetic reaction centers (RCs) and effectively dissipates its triplet excitation energy. Sensitized cis-to-trans isomerization was proposed as a possible mechanism for a singlet-triplet energy crossing for the 15,15'-cis-SPO; however, it has been questioned recently. To understand the dissipative photoprotective mechanism of this important SPO and to overcome the existing controversies on this issue, we carried out a theoretical investigation using density functional theory on the possible triplet energy relaxation mechanism through the cis-to-trans isomerization. Together with the earlier experimental observations, the possible mechanism was discussed for the triplet energy relaxation of the...

  5. Morphology-dependent photocatalytic activity of octahedral anatase particles prepared by ultrasonication-hydrothermal reaction of titanates

    Wei, Zhishun; Kowalska, Ewa; Verrett, Jonathan; Colbeau-Justin, Christophe; Remita, Hynd; Ohtani, Bunsho
    Octahedral anatase particles (OAPs) were prepared by an ultrasonication (US) hydrothermal (HT) reaction of partially proton-exchanged potassium titanate nanowires (TNWs). The structural/physical properties of OAP-containing samples, including specific surface area, crystallinity, crystallite size, particle aspect ratio, composition and total OAP content, were analyzed. Photocatalytic activities of samples were measured under irradiation (>290 nm) for oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H-2 system) under aerobic and deaerated conditions, respectively. Total density of electron traps (ETs) was measured by double-beam photoacoustic spectroscopy (DB-PAS). Mobility and lifetime of charge carriers (electrons) were investigated by the time-resolved microwave conductivity...

  6. Improvement of a Real Gas-Sensor for the Origin of Methane Selectivity Degradation by mu-XAFS Investigation

    Wada, Takahiro; Murata, Naoyoshi; Suzuki, Takuya; Uehara, Hiromitsu; Nitani, Hiroaki; Niwa, Yasuhiro; Uo, Motohiro; Asakura, Kiyotaka
    We have directly investigated the chemical state of the Pd species in a real mu-gas sensor device by examining the mu-fluorescence X-ray absorption fine structure. The mu-gas sensor device was heavily damaged by a heating process in which the temperature was ill-controlled, resulting in decrease of methane selectivity. We found that the PdO in the fresh mu-gas sensor was reduced to Pd metal particles as the methane selectivity decreased. Based on the investigation results, we modified the device structure so as to heat up homogeneously. The lifetime of the sensor was then successfully increased by more than 5 years.

  7. Dehydration of sorbitol to isosorbide over H-beta zeolites with high Si/Al ratios

    Kobayashi, Hirokazu; Yokoyama, Haruka; Feng, Bo; Fukuoka, Atsushi
    Conversion of sorbitol to isosorbide by heterogeneous catalysts is a challenge in biorefinery. Herein, H-beta zeolites with specific Si/Al ratios uniquely give isosorbide in up to 76% yield under mild conditions. Mechanistic study has suggested that acid sites on hydrophobic internal surface are active for this reaction.

  8. A high-temperature in situ cell with a large solid angle for fluorescence X-ray absorption fine structure measurement

    Murata, Naoyoshi; Kobayashi, Makoto; Okada, Yukari; Suzuki, Takuya; Nitani, Hiroaki; Niwa, Yasuhiro; Abe, Hitoshi; Wada, Takahiro; Mukai, Shingo; Uehara, Hiromitsu; Ariga, Hiroko; Takakusagi, Satoru; Asakura, Kiyotaka
    We present the design and performance of a high-temperature in situ cell with a large solid angle for fluorescence X-ray absorption fine structure (XAFS) spectra. The cell has a large fluorescence XAFS window (116 mm(phi)) near the sample in the cell, realizing a large half-cone angle of 56 degrees. We use a small heater (25 x 35 mm(2)) to heat the sample locally to 873 K. We measured a Pt-SnO2 thin layer on a Si substrate at reaction conditions having a high activity. In situ measurement enables the analysis of the difference XAFS spectra between before and during the reaction...

  9. Matrix site effects on vibrational frequencies of HXeCCH, HXeBr, and HXeI: a hybrid quantum-classical simulation

    Niimi, Keisuke; Taketsugu, Tetsuya; Nakayama, Akira
    The matrix shifts of the H-Xe stretching frequency of noble-gas hydrides, HXeCCH, HXeBr, and HXeI in various noble-gas matrices (in Ne, Ar, Kr, and Xe matrices) are investigated via the hybrid quantum-classical simulations. The order of the H-Xe stretching frequencies is found to be v(gas) < v(Ne) < v(Xe) < v(Kr) < v(Ar) for HXeCCH and HXeBr, while it is v(gas) < v(Ne) < v(Xe) < v(Ar) < v(Kr) for HXeI. This order is anomalous with respect to the matrix dielectric constants, and the calculated results reproduce the experimentally observed shifts quite successfully. We also find that the matrix shifts...

  10. Excited-State Relaxation of Hydrated Thymine and Thymidine Measured by Liquid-Jet Photoelectron Spectroscopy: Experiment and Simulation

    Buchner, Franziska; Nakayama, Akira; Yamazaki, Shohei; Ritze, Hans-Hermann; Luebcke, Andrea
    Time-resolved photoelectron spectroscopy is performed on thymine and thymidine in aqueous solution to study the excited-state relaxation dynamics of these molecules. We find two contributions with sub-ps lifetimes in line with recent excited-state QM/MM molecular dynamics simulations (J. Chem. Phys. 2013, 139, 214304). The temporal evolution of ionization energies for the excited pi pi* state along the QM/MM molecular dynamics trajectories were calculated and are compatible with experimental results, where the two contributions correspond to the relaxation paths in the pi pi* state involving different conical intersections with the ground state. Theoretical calculations also show that ionization from the n...

  11. An Investigation of Ni2P Single Crystal Surfaces : Structure, Electronic State and Reactivity

    Yuan, Qiuyi; Ariga, Hiroko; Asakura, Kiyotaka
    Ni2P has demonstrated high catalytic activity for hydrodesulfurization and has recently been employed as a catalyst in a variety of other reactions. We have thoroughly reviewed the literature concerning Ni2P single crystal surfaces, with the aim of determining the relationship between surface structure and catalytic properties. Published results to date indicate that Ni2P single crystal surfaces exhibit reconstructed structures, and so the bulk terminated structure may not be stable. We have also reviewed the surface structures and electronic states of (1 x 1) and reconstructed Ni2P(0001) and (1010). Based on these reviews, this paper presents general rules regarding stabilization of...

  12. Ring-opening polymerization of a 2,3-disubstituted oxirane leading to a polyether having a carbonyl-aromatic pi-stacked structure

    Merlani, Maia; Koyama, Yasuhito; Sato, Hiroyasu; Geng, Li; Barbakadze, Vakhtang; Chankvetadze, Bezhan; Nakano, Tamaki
    2-Methoxycarbonyl-3-(3,4-dimethoxyphenyl) oxirane was synthesized and polymerized using a cationic initiator to afford a polymer having a rather stiff, stretched conformation. The side-chain methoxycarbonyl group and 3,4-dimethoxyphenyl group of neighboring monomeric units may form a hetero pi-stacked structure between side-chain carbonyl and aromatic groups which leads to intramolecular charge transfer (ICT) interactions. 2-Ethoxy-carbonyl- 3-phenyloxirane failed in polymerization, leading only to small molecules including cyclic compounds.

  13. A high triplet-energy polymer : synthesis and photo-physical properties of a pi-stacked vinyl polymer having a xanthone moiety in the side chain

    Sugino, Hiroyoshi; Koyama, Yasuhito; Nakano, Tamaki
    Poly(xanthon-3-ylmethacrylate) (poly(XOMA))and poly(xanthon-3-yl methacrylate-co-methyl methacrylate) (poly(XOMA-co-MMA)) having a pi-stacked conformation were synthesized as host material candidates for phosphorescence-based light emitting diodes. Poly(XOMA) harvested photo excitation energy for blue phosphorescent emission of iridium bis[(4,6-difluorophenyl) pyridinato-N, C-2] picolinate (FIrpic) in a CHCl3 solution and in film.

  14. HXeI and HXeH in Ar, Kr, and Xe matrices: Experiment and simulation

    Zhu, Cheng; Niimi, Keisuke; Taketsugu, Tetsuya; Tsuge, Masashi; Nakayama, Akira; Khriachtchev, Leonid
    Experimental and theoretical studies of HXeI and HXeH molecules in Ar, Kr, and Xe matrices are presented. HXeI exhibits the H-Xe stretching bands at 1238.0 and 1239.0 cm(-1) in Ar and Kr matrices, respectively, that are blue-shifted from the HXeI band observed in a Xe matrix (1193 cm(-1)) by 45 and 46 cm(-1). These shifts are larger than those observed previously for HXeCl (27 and 16 cm(-1)) and HXeBr (37 and 23 cm(-1)); thus, the matrix effect is stronger for less stable molecules. The results for HXeI are qualitatively different from all previous results on noble-gas hydrides with respect to...

  15. Quantum mechanical molecular interactions for calculating the excitation energy in molecular environments : a first-order interacting space approach

    Hasegawa, Jun-ya; Yanai, Kazuma; Ishimura, Kazuya
    Intermolecular interactions regulate the molecular properties in proteins and solutions such as solvatochromic systems. Some of the interactions have to be described at an electronic-structure level. In this study, a commutator for calculating the excitation energy is used for deriving a first-order interacting space (FOIS) to describe the environmental response to solute excitation. The FOIS wave function for a solute-in-solvent cluster is solved by second-order perturbation theory. The contributions to the excitation energy are decomposed into each interaction and for each solvent.

  16. Exploring the catalytic properties of supported palladium catalysts in the transfer hydrogenolysis of glycerol

    Mauriello, F.; Ariga, H.; Musolino, M.G.; Pietropaolo, R.; Takakusagi, S.; Asakura, K.
    The transfer hydrogenolysis of glycerol promoted by supported palladium catalysts is reported. The reactions were carried out under mild conditions (453K and 5 bar of N-2) in absence of added hydrogen by using the reaction solvent, 2-propanol, as hydrogen source. The catalytic results are interpreted in terms of metal (Pd)-metal (Co or Fe) interaction that modifies the electronic properties of palladium and affords bimetallic PdM sites (M= Co or Fe), thus enhancing the catalytic properties of the systems in the conversion of glycerol as well as in the selectivity to 1,2-propanediol and 1-propanol. The transfer hydrogenolysis mechanism is here elucidated...

  17. Influence of post-treatment operations on structural properties and photocatalytic activity of octahedral anatase titania particles prepared by an ultrasonication-hydrothermal reaction

    Wei, Zhishun; Kowalska, Ewa; Ohtani, Bunsho
    The influence of changes in structural and physical properties on the photocatalytic activity of octahedral anatase particles (OAPs), exposing eight equivalent {101} facets, caused by calcination (2 h) in air or grinding (1 h) in an agate mortar was studied with samples prepared by ultrasonication (US; 1 h)-hydrothermal reaction (HT; 24 h, 433 K). Calcination in air at temperatures up to 1173 K induced particle shape changes, evaluated by aspect ratio (AR; d(001)/d(101) = depth vertical to anatase {001} and {101} facets estimated by the Scherrer equation with data obtained from X-ray diffraction (XRD) patterns) and content of OAP and...

  18. Electrodeposition study on a single-crystal titanium dioxide electrode : platinum on a niobium-doped titanium dioxide(110) electrode

    Takakusagi, Satoru; Ogawa, Takafumi; Uehara, Hiromitsu; Ariga, Hiroko; Shimizu, Ken-ichi; Asakura, Kiyotaka
    Pt was successfully electrodeposited on a Nb-doped TiO2(110) electrode from a solution of 1 mM K-2[PtCl4] and 50 mM H2SO4 using single-pulse chronoamperometry. The morphology of the deposited Pt nanoparticles was sensitive to the deposition potential and holding time. A novel method for the preparation of metal particles on a single-crystal TiO2 surface in a controlled manner has been proposed.

  19. Preparation of highly dispersed Pt nanoparticles supported on zeolite-templated carbon and catalytic application in hydrogenation reaction

    Jiang, Chuanxia; Hara, Kenji; Namba, Kotaro; Kobayashi, Hirokazu; Ittisanronnachai, Somlak; Nishihara, Hirotomo; Kyotani, Takashi; Fukuoka, Atsushi
    Zeolite-templated carbon (ZTC) was utilized to prepare Pt nanoparticles as a support by using a simple impregnation method. The choice of a cationic Pt precursor led to the formation of highly and uniformly dispersed Pt nanoparticles on ZTC, which afforded high conversion in the catalytic hydrogenation of phenylacetylene.

  20. A new spectroelectrochemical cell for in situ measurement of Pt and Au K-edge X-ray absorption fine structure

    Kaito, Takahiro; Mitsumoto, Hisashi; Sugawara, Seiho; Shinohara, Kazuhiko; Uehara, Hiromitsu; Ariga, Hiroko; Takakusagi, Satoru; Asakura, Kiyotaka
    A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge...

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