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971.
Hatakeyama T Hashimoto S Seki S Nakamura M 《Journal of the American Chemical Society》2011,133(46):18614-18617
A tandem intramolecular electrophilic arene borylation reaction has been developed for the synthesis of BN-fused polycyclic aromatic compounds such as 4b-aza-12b-boradibenzo[g,p]chrysene (A) and 8b,11b-diaza-19b,22b-diborahexabenzo[a,c,fg,j,l,op]tetracene. These compounds adopt a twisted conformation, which results in a tight and offset face-to-face stacking array in the solid state. Time-resolved microwave conductivity measurements prove that the intrinsic hole mobility of A is comparable to that of rubrene, one of the most commonly used organic semiconductors, indicating that BN-substituted PAHs are potential candidates for organic electronic materials. 相似文献
972.
Chiral aluminum Lewis acid catalyst composed of Me(3)Al and 3,3'-bis(trimethylsilyl)-BINOL in a 2:1 ratio was found to promote novel catalytic asymmetric ring expansion of cyclohexanone with α-substituted α-diazoacetates to give seven-membered rings with an all-carbon quaternary center. Application of this strategy to 4-substituted cyclohexanones opened up a novel way for the catalytic desymmetrizing asymmetric construction of cycloheptanones bearing remote α,δ-chiral centers. 相似文献
973.
Zenta Kato Jagadeesh BhattaraiNaokazu Kumagai Koichi IzumiyaKoji Hashimoto 《Applied Surface Science》2011,257(19):8230-8236
For the anode composed of electrocatalyst oxide, intermediate layer and titanium substrate, the substitution of a certain amount of iridium with tin in the IrO2 intermediate layer was remarkably effective in elongating the life of the anode in preventing oxidation of the substrate titanium during oxygen evolution. The longest life was realized by preparation of intermediate layer with uniform thickness by brush-coating of H2IrCl6-SnCl4 butanol solution and subsequent calcination. The anode with the intermediate layer prepared from 0.04 M H2IrCl6-0.06 M SnCl4 butanol solution showed the best performance, that is, the oxygen evolution efficiency higher than 99.8% for more than 4300 h in the electrolysis of 0.5 M NaCl solution of pH 1 at the current density of 1000 Am−2. An increase in SnCl4 concentration decreased the viscosity of the coating solution with a consequent enhancement of uniformity of the intermediate layer but decreased the thickness of the intermediate layer acting as a barrier to prevent oxidation of titanium. Thus, the best performance was attained at an intermediate SnCl4 concentration. The growth of an oxide layer on titanium during electrolysis occurred and was found by the potential increase. 相似文献
974.
Evaluation of stability of Pr2−xNdxNiO4+δ by thermogravimetry under various oxygen partial pressures
Sakai Mamoru Wang Chengkun Okiba Takashi Soga Haruki Hashimoto Takuya 《Journal of Thermal Analysis and Calorimetry》2020,142(1):139-147
Journal of Thermal Analysis and Calorimetry - The thermodynamic and kinetic stability of Pr2?xNdxNiO4+δ was evaluated by thermogravimetry (TG) under a varying oxygen partial pressure... 相似文献
975.
Yusuke Ishigaki Takumi Hashimoto Kazuma Sugawara Shuichi Suzuki Takanori Suzuki 《Angewandte Chemie (International ed. in English)》2020,59(16):6581-6584
Thermally switchable redox properties have been reported to be due to a change in the spin state of newly designed overcrowded ethylenes, which can adopt closed‐shell folded and open‐shell twisted forms. In this study, tetrathienylanthraquinodimethane derivatives were designed to be in thermal equilibrium between a more stable folded form and less stable but more donating twisted diradical in solution, so that the oxidation potential can be controlled by heating/cooling. This is the first example of a switching of redox properties based on a thermally equilibrated twisted diradical, which can be more readily oxidized to the twisted dication. 相似文献
976.
Seangaroon Yoiprommarat Surisa Kongthong Wilunda Choowong Nattawut Boonyuen Masahiko Isaka 《Natural product research》2020,34(9):1233-1237
AbstractFour xanthones (1?4) and a known compound, mansonone D (5), were isolated from the lignicolous freshwater fungus BCC 28210 (family, Chaetosphaeriaceae). The structures of these compounds were elucidated by extensive spectroscopic analysis. Among the isolated metabolites, compound 2 and the known mansonone D (5) displayed antimalarial activity against Plasmodium falciparum K1 with IC50 values of 7.75 and 0.55?μg/mL, respectively. Compound 4 displayed antibacterial activity against Bacillus cereus with an MIC value of 6.25?μg/mL. 相似文献
977.
Dr. Akitaka Ito Akihiro Shimizu Noriaki Kishida Yusuke Kawanaka Dr. Daisuke Kosumi Prof. Dr. Hideki Hashimoto Prof. Dr. Yoshio Teki 《Angewandte Chemie (International ed. in English)》2014,53(26):6715-6719
The excited‐state dynamics of pentacene derivatives with stable radical substituents were evaluated in detail through transient absorption measurements. The derivatives showed ultrafast formation of triplet excited state(s) in the pentacene moiety from a photoexcited singlet state through the contributions of enhanced intersystem crossing and singlet fission. Detailed kinetic analyses for the transient absorption data were conducted to quantify the excited‐state characteristics of the derivatives. 相似文献
978.
Multicolour Fluorescent Memory Based on the Interaction of Hydroxy Terphenyls with Fluoride Anions
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Masaaki Akamatsu Dr. Taizo Mori Dr. Ken Okamoto Prof. Dr. Hideki Sakai Prof. Dr. Masahiko Abe Dr. Jonathan P. Hill Prof. Dr. Katsuhiko Ariga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16293-16300
Memory operations based on variation of a molecule’s properties are important because they may lead to device miniaturization to the molecular scale or increasingly complex information processing protocols beyond the binary level. Molecular memory also introduces possibilities related to information‐storage security where chemical information (or reagents) might be used as an encryption key, in this case, acidic/basic reagents. Chemical memory that possesses both volatile and non‐volatile functionality requires reversible conversion between at least two chemically different stable or quasi‐stable states. Here we have developed the phenol–phenoxide equilibrium of phenol fluorophores as a data storage element, which can be used to write or modulate data using chemical reagents. The properties of this system allow data to be stored and erased either in non‐volatile or volatile modes. We also demonstrate non‐binary switching of states made possible by preparation of a composite containing the molecular memory elements. 相似文献
979.
Universal Reaction Mechanism of Boronic Acids with Diols in Aqueous Solution: Kinetics and the Basic Concept of a Conditional Formation Constant
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Yuki Furikado Tomomi Nagahata Takuya Okamoto Dr. Tomoaki Sugaya Prof. Dr. Satoshi Iwatsuki Prof. Dr. Masahiko Inamo Prof. Dr. Hideo D. Takagi Prof. Dr. Akira Odani Prof. Dr. Koji Ishihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13194-13202
To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (${K{{{\rm BL}\hfill \atop {\rm a}\hfill}}}$ ) of boronic acid diol esters (HBLs) were determined based on the well‐established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4‐difluorophenylboronic acid and chromotropic acid, 3‐nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b) the determined pKa values of HBLs. The use of the conditional formation constant, K′, based on the main reaction: RB(OH)2+H2L ${{\mathop \leftrightarrow \limits ^{K{_{1}}}_{}}}$ RB(L)(OH)?+H3O+ instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B′) with uncomplexed diol species (L′) to form boronic acid diol complex species (esters, BL′) in aqueous solution at pH 5–11: B′+L′ ${{\mathop \leftrightarrow \limits ^{K{^\prime}}_{}}}$ BL′. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution. 相似文献
980.
Direct α‐Siladifluoromethylation of Lithium Enolates with Ruppert‐Prakash Reagent via CF Bond Activation
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Ryota Hashimoto Toshiaki Iida Dr. Kohsuke Aikawa Prof. Dr. Shigekazu Ito Prof. Dr. Koichi Mikami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2750-2754
The direct α‐siladifluoromethylation of lithium enolates with the Ruppert–Prakash reagent (CF3TMS) is shown to construct the tertiary and quaternary carbon centers. The Ruppert–Prakash reagent, which is versatile for various trifluoromethylation as a trifluoromethyl anion (CF3?) equivalent, can be employed as a siladifluoromethyl cation (TMSCF2+) equivalent by C?F bond activation due to the strong interaction between lithium and fluorine atoms. 相似文献