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排序方式: 共有1178条查询结果,搜索用时 31 毫秒
61.
Kei Ohkubo Kentaro Mizushima Shunichi Fukuzumi 《Research on Chemical Intermediates》2013,39(1):205-220
Efficient photocatalytic oxygenation of toluene occurs under visible light irradiation of 9-mesityl-10-methylacridinium (Acr+–Mes) in oxygen-saturated acetonitrile containing toluene and aqueous hydrochloric acid with a xenon lamp for 15 h. The oxygenated products, benzoic acid (70 %) and benzaldehyde (30 %), were formed after the photoirradiation. The photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of the Acr+ moiety of Acr+–Mes, which affords the electron-transfer state, Acr?–Mes?+. The Mes?+ moiety can oxidize chloride ion (Cl?) by electron transfer to produce chlorine radical (Cl?), whereas the Acr? moiety can reduce O2 to O 2 ?? . The Cl? radical produced abstracts a hydrogen from toluene to afford benzyl radical in competition with the bimolecular radical coupling of Cl?. The benzyl radical reacts with O2 rapidly to afford the peroxyl radical, leading to the oxygenated product, benzaldehyde. Benzaldehyde is readily further photooxygenated to yield benzoic acid with Acr?–Mes?+. In the case of an aromatic compound with electron-donating substituents, 1,3,5-trimethoxybenzene, photocatalytic chlorination occurred efficiently under the same photoirradiation conditions to yield a monochloro-substituted compound, 2,4,6-trimethoxychlorobenzene. 相似文献
62.
Masahide Tominaga Hiroyuki Ukai Kosuke Katagiri Kazuaki Ohara Kentaro Yamaguchi Isao Azumaya 《Tetrahedron》2014
Five macrocyclic molecules (1–5) were efficiently synthesized from the dimerization and trimerization of di-substituted adamantane derivatives, which were composed of three different aromatic units and two different linker groups. Three single-crystals were obtained from these macrocyclic molecules, including a set of pseudopolymorphs (3a and 3b) of macrocycle 3 and another macrocycle 5 (5a). Single crystal X-ray analysis revealed that the three monocyclic compounds were rectangular or square in shape with solvent molecules in the cavity. Macrocycle 3 in 3a formed stacks to produce tubular structures with channels that assembled into three-dimensional networks through CH/π interactions. 相似文献
63.
Motivated by recent graphene transport experiments, we undertake a numerical study of the conductivity of disordered two-dimensional massless Dirac fermions. Our results reveal distinct differences between the cases of short-range and Coulomb randomly distributed scatterers. We speculate that this behavior is related to the Boltzmann transport theory prediction of dirty-limit behavior for Coulomb scatterers. 相似文献
64.
A Doping Technique that Suppresses Undesirable H2 Evolution Derived from Overall Water Splitting in the Highly Selective Photocatalytic Conversion of CO2 in and by Water 下载免费PDF全文
Prof. Dr. Kentaro Teramura Zheng Wang Dr. Saburo Hosokawa Prof. Dr. Yoshihisa Sakata Prof. Dr. Tsunehiro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):9906-9909
Photocatalytic conversion of CO2 to reduction products, such as CO, HCOOH, HCHO, CH3OH, and CH4, is one of the most attractive propositions for producing green energy by artificial photosynthesis. Herein, we found that Ga2O3 photocatalysts exhibit high conversion of CO2. Doping of Zn species into Ga2O3 suppresses the H2 evolution derived from overall water splitting and, consequently, Zn‐doped, Ag‐modified Ga2O3 exhibits higher selectivity toward CO evolution than bare, Ag‐modified Ga2O3. We observed stoichiometric amounts of evolved O2 together with CO. Mass spectrometry clarified that the carbon source of the evolved CO is not the residual carbon species on the photocatalyst surface, but the CO2 introduced in the gas phase. Doping of the photocatalyst with Zn is expected to ease the adsorption of CO2 on the catalyst surface. 相似文献
65.
The CyanoP protein is a cyanobacterial homolog of the PsbP protein, which is an extrinsic subunit of photosystem II (PSII) in green plant species. The molecular function of CyanoP has been investigated in mutant strains of Synechocystis but inconsistent results have been reported by different laboratories. In this study, we generated and characterized a Synechocystis mutant in which entire region of the CyanoP gene was eliminated. After repeated subculture in CaCl2-depleted medium, growth retardation was clearly observed for a CyanoP knockout mutant of Synechocystis sp. PCC 6803 (?P). The PSII-mediated oxygen-evolving activity of the ?P cells was more susceptible to depletion of CaCl2 than that of wild-type cells. The 77 K fluorescence emission spectra indicated that energy coupling between phycobilisome and PSII was perturbed in both wild-type and ?P cells under CaCl2-depleted conditions, and was more evident for the ?P mutant. To examine the association of CyanoP with PSII complexes, we tested several detergents for solubilization of thylakoid membranes and showed that CyanoP was partly included in fractions containing large protein complexes in gel-filtration analysis. These results indicate that CyanoP constitutively stabilizes PSII functionality in vivo. 相似文献
66.
Tomohiro Seki Chi Feng Kentaro Kashiyama Shunichi Sakamoto Yuichi Takasaki Toshiyuki Sasaki Satoshi Takamizawa Hajime Ito 《Angewandte Chemie (International ed. in English)》2020,59(23):8839-8843
Ferroelasticity has been reported for several types of molecular crystals, which show mechanical‐stress‐induced shape change under twinning and/or spontaneous formation of strain. Aiming to create materials that exhibit both ferroelasticity and light‐emission characteristics, we discovered the first examples of ferroelastic luminescent organometallic crystals. Crystals of arylgold(I)(N‐heterocyclic carbene)(NHC) complexes bend upon exposure to anisotropic mechanical stress. X‐ray diffraction analyses and stress‐strain measurements on these ferroelastic crystals confirmed typical ferroelastic behavior, mechanical twinning, and the spontaneous build‐up of strain. A comparison with single‐crystal structures of related gold‐NHC complexes that do not show ferroelasticity shed light on the structural origins of the ferroelastic behavior. 相似文献
67.
Optical Review - We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain... 相似文献
68.
Kentaro Yonesato Hiroyasu Ito Daisuke Yokogawa Kazuya Yamaguchi Kosuke Suzuki 《Angewandte Chemie (International ed. in English)》2020,59(38):16361-16365
Small Agn nanoclusters (n<10) have been emerging as promising materials as sensing, biolabeling, and catalysis because of their unique electronic states and optical properties. However, studying synthesis, structure determination, and exploration of their properties remain major challenges as a result of the low stability of small Ag nanoclusters. Herein, we synthesized an atomically precise face‐centered‐cubic‐type small {Ag7}5+ nanocluster supported by a novel triangular hollow polyoxometalate (POM) framework [Si3W27O96]18?. The cluster showed unique {Ag7}5+‐to‐POM charge transfer bands in both visible and UV light regions. Furthermore, this small {Ag7}5+ nanocluster exhibited an unprecedented ultrastability in solution, despite having exposed Ag sites that can be accessed by small molecules, such as O2, water, and solvents. 相似文献
69.
Total synthesis of pyrroloquinoline alkaloids, such as makaluvamine A/D, damirone B, batzelline C, makaluvone, and isobatzelline C, was achieved featuring a one-pot benzyne-mediated cyclization-functionalization reaction. The synthetic utility was demonstrated by the construction of the common pyrrolo[4,3,2-de]quinoline skeleton. 相似文献
70.