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831.
832.
An ab initio molecular dynamics approach is combined with the semiclassical tunneling method of Makri and Miller, which is applied to estimations of tunneling splitting in the umbrella inversion of ammonia and the intramolecular hydrogen transfer in malonaldehyde. In the application to malonaldehyde, effects of multidimensionality are examined by assigning quantum zero-point energies only to significant vibrational modes and changing the amount of energy given to other degrees of freedom. The calculated tunneling splitting values are in good agreement with the corresponding experimental values for both molecules. 相似文献
833.
Kawatsuki N Miki H Kondo M Nakamura M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(9):4534-4542
Reversible addition-fragmentation chain transfer (RAFT) polymerization is used to synthesize diblock and random copolymers of poly[(2-trifluoroethyl methacrylate)-co-(methacrylic acid)]. Copolymer films doped with fluorene derivatives comprised of pyridine groups exhibit reversible photoluminescent (PL) color tuning by adjusting the location of fluorene derivatives in H-bonds or non-H-bonds environments. The composite films exhibit green and blue photoluminescence with and without effective H-bonding between the pyridine ring in the fluorene derivative and the carboxylic acid side group, respectively. At elevated temperatures, the H-bonded structure dissociates and the fluorene derivative migrates to the hydrophobic block in the diblock polymer, and they do not form H-bonds upon cooling. However, re-formation of H-bonds also occurs upon cooling random copolymers. Moreover, adjusting the annealing temperature and the solvent annealing reversibly tunes the PL color in the diblock copolymer composite films. 相似文献
834.
Osaki Toshihiko Yamada Kiho Watari Koji Tajiri Koji Shima Saori Miki Takeshi Tai Yutaka 《Journal of Sol-Gel Science and Technology》2012,61(1):268-274
Alumina cryogels were synthesized from a colloidal boehmite sol through a sol–gel processing and subsequent freeze drying,
and thermal stability was examined by comparison to that of the corresponding xerogel, precipitate and commercial alumina.
N2 adsorption, X-ray powder diffraction and transmittance electron micrography observations revealed that the stability was
higher for the cryogel than for others in particular at temperatures above 1,000 °C. The higher stability was ascribed to
the fine and uniform primary particles with fibrous shapes formed by the sol–gel technique and furthermore to the suppression
of aggregation of the primary particles owing to the subsequent freeze drying. It was also found that aluminum sec-butoxide
employed as a precursor for the preparation of boehmite sol was preferable compared to aluminum iso-propoxide. 相似文献
835.
Miki Horie Yosuke Hayashi Dr. Shigeru Yamaguchi Prof. Dr. Hiroshi Shinokubo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):5919-5923
Synthesis of nickel(II) complexes of meso‐aryl‐substituted azacorroles was performed by Buchwald–Hartwig amination of a dipyrrin NiII complex with benzylamine through C? N and C? C coupling. The highly planar structure of NiII azacorroles was elucidated by X‐ray diffraction analysis. 1H NMR analysis and nucleus independent chemical shift (NICS) calculation on NiII azacorrole revealed its distinct aromaticity with [17]triaza‐annulene 18π conjugation. In addition, acylation of azacorrole selectively afforded N‐ and C‐acylated azacorroles depending on the reaction conditions, showing the dual reactivity of azacorroles. 相似文献
836.
Prof. Dr. Shunichi Fukuzumi Takuya Mizuno Tetsuya Ojiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15794-15804
Manganese(V)–oxo–porphyrins are produced by the electron‐transfer oxidation of manganese–porphyrins with tris(2,2′‐bipyridine)ruthenium(III) ([Ru(bpy)3]3+; 2 equiv) in acetonitrile (CH3CN) containing water. The rate constants of the electron‐transfer oxidation of manganese–porphyrins have been determined and evaluated in light of the Marcus theory of electron transfer. Addition of [Ru(bpy)3]3+ to a solution of olefins (styrene and cyclohexene) in CH3CN containing water in the presence of a catalytic amount of manganese–porphyrins afforded epoxides, diols, and aldehydes efficiently. Epoxides were converted to the corresponding diols by hydrolysis, and were further oxidized to the corresponding aldehydes. The turnover numbers vary significantly depending on the type of manganese–porphyrin used owing to the difference in their oxidation potentials and the steric bulkiness of the ligand. Ethylbenzene was also oxidized to 1‐phenylethanol using manganese–porphyrins as electron‐transfer catalysts. The oxygen source in the substrate oxygenation was confirmed to be water by using 18O‐labeled water. The rate constant of the reaction of the manganese(V)–oxo species with cyclohexene was determined directly under single‐turnover conditions by monitoring the increase in absorbance attributable to the manganese(III) species produced in the reaction with cyclohexene. It has been shown that the rate‐determining step in the catalytic electron‐transfer oxygenation of cyclohexene is electron transfer from [Ru(bpy)3]3+ to the manganese–porphyrins. 相似文献
837.
Prof. Masamichi Yamanaka Kazushige Yanai Yusuke Zama Junko Tsuchiyagaito Dr. Masaru Yoshida Dr. Ayumi Ishii Prof. Miki Hasegawa 《化学:亚洲杂志》2015,10(6):1299-1303
Hierarchical self‐assembly of an amphiphilic tris‐urea in aqueous media is shown. A mixture of the amphiphilic tris‐urea and an alkaline solution gave a viscous solution composed of fibrous aggregates. This viscous solution transformed into supramolecular hydrogels, which are capable of hierarchically organizing into higher‐order aggregates in response to several cationic triggers. The resulting supramolecular hydrogels were relatively stiff and their storage moduli attained over 103 Pa. The stimuli‐responsive and optical properties of the resulting hydrogels were influenced by the cationic trigger. Proton and calcium ion triggers gave pH‐ and chemical stimuli‐responsive hydrogels, respectively. A terbium ion trigger also provided a highly luminescent hydrogel through energy transfer from the tris‐urea to terbium. 相似文献
838.
Tetsuya Sengoku 《Tetrahedron letters》2009,50(34):4937-4417
Synthesis and structural confirmation of highly oxygenated pyrrolizidine alkaloids, hyacinthacines C2 [(1S,2R,3R,5R,7S,7aR)-3,5-hydroxymethyl-1,2,7-trihydroxypyrrolizidine], C3[(1S,2R,3R,5S,7R,7aR)-3,5-hydroxymethyl-1,2,7-trihydroxypyrrolizidine], and their C5-epimers were achieved on the basis of the highly divergent method employing (S)-(−)-2-pyrrolidone-5-carboxylic acid as the starting material. 相似文献
839.
Kengo Shimanoe Aya Nishiyama Masayoshi Yuasa Tetsuya Kida Noboru Yamazoe 《Procedia Chemistry》2009,1(1):212-215
To fabricate more excellent NO2 sensor with high sensor response and good linearity between the sensor response and NO2 concentration, the microstructure of WO3 lamellae was controlled by adding nano-particles of SnO2. It was found that the sintering of WO3 lamellae was inhibited by adding nano-particles of SnO2. The device using WO3 lamellae added a small amount of SnO2 nano-particles had the highest sensor response, exhibiting a high sensor response (S = 60-540) even to dilute NO2 (100–1000 ppb) in air at 200°C. 相似文献
840.