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排序方式: 共有249条查询结果,搜索用时 31 毫秒
101.
Suguru Ohta Masayoshi Nakano Takashi Kubo Kenji Kamada Koji Ohta Ryohei Kishi Nozomi Nakagawa Benoît Champagne Edith Botek Shin-ya Umezaki Akihito Takebe Hideaki Takahashi Shin-ichi Furukawa Yasushi Morita Kazuhiro Nakasuji Kizashi Yamaguchi 《Chemical physics letters》2006,420(4-6):432-437
The static second hyperpolarizability (γ) of a singlet diradical system involving phenalenyl radicals linked with acetylene π-conjugated bridge, BPLE, is investigated as well as reference closed-shell systems, BPRY1 and BPRY2, by the hybrid density functional theory method. The γ value of BPLE with intermediate diradical character is shown to be about four times as large as that of BPRY1 with similar π-conjugation length and to be about twice as large as that of BPRY2 with longer π-conjugation length. This feature is in agreement with our prediction that the molecules with intermediate diradical characters enhance γ values compared to the closed-shell molecules. 相似文献
102.
Zhan Jie Wang Hirokazu Usuki Toshihide Kumagai Hiroyuki Kokawa 《Journal of Sol-Gel Science and Technology》2007,42(3):375-379
(La0.7Sr0.3)MnO3 thin films were deposited on SiO2/Si substrates by a metal-organic decomposition (MOD) method, and then Pb(Zr0.52Ti0.48)O3 (PZT) thin films were grown on (La0.7Sr0.3)MnO3-coated SiO2/Si substrates by a sol-gel method. The effects of annealing temperature on the crystalline phases, microstructures and electrical
properties of the PZT films were investigated. X-ray diffraction analysis results indicated that the PZT films with a perovskite
single phase could be obtained by annealing at 650°C. The dielectric constant and the remnant polarization of the PZT films
increased with increasing annealing temperature. The remnant polarization and the coercive field of the films annealed at
650°C were 18.3 μC/cm2 and 35.5 kV/cm, respectively, whereas the dielectric constant and loss value measured at 1 kHz were approximately 1100 and
0.81, respectively. 相似文献
103.
Watanabe T Tanaka Y Shoda R Sakamoto R Kamikawa K Uemura M 《The Journal of organic chemistry》2004,69(12):4152-4158
Naphthyl tetrahydroisoquinoline alkaloids, atropisomeric korupensamines A and B and ent-korupensamine B, were synthesized by syn-selective cross-coupling of a planar chiral arene chromium complex with naphthylboronic acid and subsequent axial isomerization or tricarbonylchromium migration to the inverted arene face as a key step. Palladium(0)-catalyzed cross-coupling of planar chiral arene chromium complex 12 with naphthylboronic acid 9 gave syn-biaryl coupling product 13. syn-Biaryl chromium complex 13 was heated in 1:1 mixture of di-n-butyl ether and 1,2-dichloroethane to give a face-inverted anti-biaryl chromium complex 14 without axial isomerization. Korupensamine A was synthesized from the syn-biaryl chromium complex 13 via o-formyl syn-biaryl chromium complex 10, and ent-korupensamine B was prepared from the face-inverted anti-biaryl chromium complex 14. On the other hand, difluoro-substituted syn-biaryl chromium complex 40 with a formyl group afforded anti-biaryl chromium complex 41 containing a rotated central bond by heating in xylene. The chromium-complexed fluorine atom was easily substituted with an isopropoxy group by nucleophilic substitution. Use of these reactions allowed (+)-2-bromo-3,5-difluorobenzaldehyde chromium complex (37) as a single chiral source to be converted to atropisomeric korupensamines A and B, respectively. 相似文献
104.
Reductive Cross‐Coupling of Conjugated Arylalkenes and Aryl Bromides with Hydrosilanes by Cooperative Palladium/Copper Catalysis 下载免费PDF全文
Dr. Kazuhiko Semba Kenta Ariyama Dr. Hong Zheng Ryohei Kameyama Prof. Dr. Shigeyoshi Sakaki Prof. Dr. Yoshiaki Nakao 《Angewandte Chemie (International ed. in English)》2016,55(21):6275-6279
A method for the reductive cross‐coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis was developed, thus resulting in the highly regioselective formation of various 1,1‐diarylalkanes, including a biologically active molecule. Under the applied reaction conditions, high levels of functional‐group tolerance were observed, and the reductive cross‐coupling of internal alkynes with aryl bromides afforded trisubstituted alkenes. 相似文献
105.
Dr. Haiwang Lai Changming Jin Dr. Junsu Park Dr. Ryohei Ikura Prof. Yoshinori Takashima Prof. Makoto Ouchi 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218597
In this study, we designed a methacrylate molecule with an alkyl-substituted trichloro salicylic acid pendant as a transformable bulky monomer to enable the synthesis of an alternating copolymer of methyl methacrylate (MMA) and n-butyl acrylate (nBA). The adamantyl-substituted methacrylate monomer ( 1-Ad ) showed very low homopolymerization propensity in radical polymerizations, but afforded the alternating copolymer with nBA via copolymerization. The 1-Ad units in the resultant copolymer were quantitatively and selectively transformed into MMA via transesterification with methanol to yield the alternating copolymer of MMA and nBA. Its alternating sequence was clearly demonstrated by a structural analysis via 13C NMR spectroscopy as well as the low reactivity ratios for the 1-Ad and nBA pair. Finally, we verified the superior self-healing ability of the alternating copolymer compared to that of the corresponding 1 : 1 statistical copolymer. 相似文献
106.
The efficient selective synthesis of secondary and tertiary amines has been achieved by means of Cp*Ir-catalyzed multialkylation of ammonium salts with alcohols without solvent: the reactions of ammonium acetate with alcohols gave tertiary amines exclusively, while those of ammonium tetrafluoroborate afforded secondary amines selectively. Using this method, secondary 5- and 6-membered cyclic amines were synthesized from ammonium tetrafluoroborate and diols in one pot. 相似文献
107.
108.
Dr. Akihito Konishi Koki Horii Haruna Iwasa Yui Okada Dr. Ryohei Kishi Prof. Dr. Masayoshi Nakano Prof. Dr. Makoto Yasuda 《化学:亚洲杂志》2021,16(12):1553-1561
The singlet open-shell character and antiaromaticity are intriguing features in π-conjugated carbocycles. These two exhibit similar chemical and physical properties. However, they rarely coexist in the same molecule. Understanding the interrelation between the open-shell and antiaromatic characteristics in the same molecule is crucial to control the electronic properties. Herein we describe the synthesis and characterization of a new member of diareno[a,f]pentalene, benzo[a]naphtho[2,3-f]pentalene 6 . Unlike its isomer 5 with a closed-shell ground state, 6 exhibits an appreciable open-shell character and a moderate antiaromatic feature. The behaviors of the open-shell index (y0) against the difference of the proton chemical signal (Δδ(H1)) between pentalenide dianions/neutral pentalenes for our reported pentalenes 1 , 4 , 5 , and 6 give a thought-provoking conclusion about the interrelation between open-shell and antiaromatic characteristics in this series. The mode of the incorporated quinoidal moiety and the formal molecular symmetry are critical to balance these two characteristics. 相似文献
109.
Artificial odorant sensors generally perform poorer than olfactory systems in living organisms. The excellent performances of living odorant systems are achieved by the molecular recognition abilities of odorant receptors and the neuronal information processing that follows. To take advantages of this, here we propose a novel hybrid odorant biosensor by means of expressing ionotropic odorant receptors of insects into dissociated neuronal cultures of rodents. This combination of materials brings significant advantages such as easy functional expression, prolonged lifetime, and an ability to amplify the weak ionic currents of odorant receptors. In the present work, pheromone receptors and co-receptors of silkmoth, i.e., BmOR1 and BmorOrco, were expressed in neuronal cultures via liposome transfection. Consequently, BmOR1 and BmorOrco were co-expressed in 8% of neuronal cells, and both receptors were co-localized on a cell membrane. In Ca++ imaging experiments, synchronous increase of calcium signals at the presentation of BOL was found in both transfected cells and non-transfected cells in a dose-dependent manner. These results provide the proof-of-concept of the proposed hybrid odorant biosensor. 相似文献
110.
T Yamaki R Ohdate E Nakadai Y Yoshihashi E Yonemochi K Terada H Moriyama K Izutsu C Yomota H Okuda T Kawanishi 《Chemical & pharmaceutical bulletin》2012,60(9):1176-1181
Component crystallization and physical collapse during freeze-drying of aqueous solutions containing protein-stabilizing L-arginine and citric acid mixtures were studied. Freeze-drying microscopy (FDM) and thermal analysis of the solute-mixture frozen solutions showed collapse onset at temperatures (T(c)) approximately 10°C higher than their T(g)'s (glass transition temperatures of the maximally freeze-concentrated solute phase). Experimental freeze-drying of these solutions at a low chamber pressure showed the occurrence of physical collapse at shelf temperatures close to or slightly higher than the T(c). Slower ice sublimation at higher chamber pressures induced the physical collapse from lower shelf temperatures. The large effect of chamber pressures on the collapse-inducing shelf temperatures confirmed significance of the sublimation-related heat loss on the sublimation interface temperature during the primary drying. Drying of the single-solute L-arginine solution resulted in cake-structure solids composed of its anhydrous crystal. Thermal and powder X-ray diffraction (PXRD) analysis suggested slow crystal nucleation of L-arginine dihydrate in the frozen solutions. Characterization of the frozen solutions and freeze-dried solids should enable rational formulation design and process control of amino acid-containing lyophilized pharmaceuticals. 相似文献