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排序方式: 共有93条查询结果,搜索用时 46 毫秒
1.
Dr. Masashi Hasegawa Chika Hasegawa Yuki Nagaya Prof. Dr. Kazunori Tsubaki Prof. Dr. Yasuhiro Mazaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202218
Chiral macrocyclic dimers, trimers, and tetramers composed of paraphenylene and tethered binaphthyl were synthesized, and their molecular structures and chiroptical properties were investigated. X-ray analysis and theoretical calculations revealed that multiple twisted molecular structures – dimers, trimers, and tetramers – adopt figure-of-eight, Möbius triangle, and concave rectangle structures, respectively. These homologues have large ϵ values in their UV-vis absorption spectra because of the π-conjugation of the naphthalene-phenylene-naphthalene frameworks. Owing to the shape-persistent ring structure and tethering with −OCH2CH2O−, high fluorescence quantum yields and a relatively high dissymmetry factor gCPL in circularly polarized luminescence (CPL) spectra were achieved. This results in CPL brightness (BCPL) of over 100, which is greater than that of the conventional organic CPL dye. 相似文献
2.
Dr. Yohei Hattori Shunsuke Tsubaki Dr. Ryota Matsuoka Dr. Tetsuro Kusamoto Prof. Hiroshi Nishihara Prof. Kingo Uchida 《化学:亚洲杂志》2021,16(17):2538-2544
Polychlorinated pyridyldiphenylmethyl radicals having substituents meta to the position bearing the carbon-centered radical (α-carbon) are synthesized. All of them are stable in ambient conditions in solutions and fluorescent in cyclohexane. The fluorescence of the radicals with bromo, phenyl, 4-chlorophenyl, or 2-pyridyl substituents are enhanced in chloroform, while the emission of the radicals with 2-thienyl or 2-furyl substituents are quenched in chloroform. DFT and TD-DFT calculations indicate that the first doublet excited states of the former are locally excited, while the first doublet excited states of the latter are charge transfer states from the π-electron-donating substituent to the accepting radical. The latter also show much higher photostability under 370-nm light irradiation compared with the first reported photostable fluorescent radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM), with pronounced bathochromic shifts of the fluorescence. 相似文献
3.
Qingde Zhang Yisheng Tan Caihong Yang Yizhuo Han Jun Shamoto Noritatsu Tsubaki 《天然气化学杂志》2007,16(3):322-325
The attractive utilization route for one-step catalytic oxidation of dimethyl ether to dimethoxymethane was successfully carried out over the H3PW12O40(40%)/SiO2 catalyst, modified by Cs, K, Ni, and V. The Cs modification of H3PW12O40(40%)/SiO2 gave the most promising result of 20% dimethyl ether conversion and 34.8% dimethoxymethane selectivity. Dimethoxymethane could be synthe- sized via methoxy groups decomposed from dimethyl ether through the synergistic effect between the acid sites and the redox sites of Cs modified H3PW12O40(40%)/SiO2. 相似文献
4.
Pieraccini S Ferrarini A Fuji K Gottarelli G Lena S Tsubaki K Spada GP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(4):1121-1126
The helical structure of the chiral nematic phases (cholesterics) obtained by doping nematic solvents with chiral non-racemic compounds is a macroscopic proof of the solute chirality. Oligonaphthalene (tetra-, hexa-, octa-) derivatives linked at the 1,4-positions have been used as chiral dopants: When the chirality axes are configurationally homogeneous (that is, all-S), the molecular structures correspond to right-handed helices. Yet, we have found series of derivatives with the surprising property that the handedness of the induced cholesteric phase alternates from positive to negative and to positive again, on passing from tetra- to hexa- and to octanaphthalene. A comparison with oligonapthalene derivatives, which do not exhibit this twisting ability, points to the importance of the substitution pattern. Both the possibility of inducing oppositely-handed cholesteric phases by homochiral helices of different length, and the role played of substituents, are confirmed by calculations performed with the surface chirality model. 相似文献
5.
H Harada K Iizuka T Kamijo K Akahane R Yamamoto Y Nakano A Tsubaki T Kubota I Shimaoka H Umeyama 《Chemical & pharmaceutical bulletin》1990,38(11):3042-3047
The experimental details for the synthesis of human renin inhibitors are described. In order to avoid metabolic degradation of the Phe-His (P3-P2) amide bond in transition-state analogs, structurally modified acyl residues (P4-P3) were incorporated into the inhibitors. Compound 1a, which contained 2-(1-naphthylmethyl)-3-(N-phenethylcarbamoyl)propionyl residue (P4-P3) with a retro-inverso amide bond, L-histidine, and norstatine isoamylamide residue (P1-P1) as a transition-state mimic, had potent human renin inhibitory activity, and it lowered blood pressure when administered orally to common marmosets. 相似文献
6.
浆态床合成二甲醚复合催化剂失活原因探索 总被引:3,自引:0,他引:3
在反应温度260 ℃、压力5.0 MPa的条件下,对浆态床反应器中二甲醚合成复合催化剂的失活规律进行了研究.结果表明,Cu基催化剂失活较快是导致浆态床二甲醚合成催化剂不稳定的主要原因.通过分析Cu基催化剂在浆态床反应器和固定床反应器中的活性变化规律,发现在浆态床反应器中不能及时导出反应体系的H2O对催化剂的毒副作用导致了浆态床Cu基催化剂快速失活.对失活催化剂进行的TPR、XRD和SEM-EDS表征结果可以看出,Cu粒子的长大和积炭是Cu基催化剂失活的重要原因,与已有文献报道不同的是并未发现明显的Cu元素流失. 相似文献
7.
Shoma Mizutani Kenta Komori Tohru Taniguchi Kenji Monde Kouji Kuramochi Kazunori Tsubaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(33):9705-9708
A biomimetic synthesis of naturally occurring lactams rubrobramide, flavipucine, and isoflavipucine is described. The key step is a regioselective Darzens reaction between isobutyl glyoxal and an α‐bromo‐β‐ketoamide. The construction of the core tricyclic ring system of rubrobramide was achieved by a cascade reaction in a single step from an α,β‐epoxy‐γ‐lactam. Furthermore, the absolute configuration of naturally occurring (+)‐rubrobramide was determined by vibrational circular dichroism. (±)‐Flavipucine and (±)‐isoflavipucine were synthesized from an epoxyimide, which was prepared by reaction of isobutyl glyoxal with a protected α‐bromo‐β‐ketoamide. Deprotection of the epoxyimide and formation of the pyridone ring gave (±)‐flavipucine, which was converted into (±)‐isoflavipucine by thermal isomerization. 相似文献
8.
Host 1 based on the phenolphthalein skeleton and two crown ether moieties demonstrated opposite behaviors toward sodium and potassium cations caused by bidirectional complexation. [reaction: see text] 相似文献
9.
Morimoto T Henmi M Naito R Tsubaki K Aoki N Bird JP Ochiai Y 《Physical review letters》2006,97(9):096801
We report on a remarkable resonance in the differential conductance of long quantum point contacts (QPCs) that is observed as a precursor to regular quantized transport. This effect is increasingly pronounced in longer QPCs, in which the differential conductance may resonantly exceed 2e2/h. From a study of the experimental characteristics of this feature, we suggest that it may be associated with the formation of a well-resolved energy gap that opens dynamically as a result of enhanced many-body interactions in long QPCs. 相似文献
10.
The design secret of Kyokusui-no-En’s meandering channel 总被引:1,自引:0,他引:1
The purpose of this study is to investigate the characteristics of the flow through the Jonangu channel which is used for
ceremonial game called as ‘Kyokusui-no-En’ in Japanese. The geometry of the channel is measured, a visualization technique
is used to measure the actual flow characteristics, and then a numerical flow model is used to represent the flow including
unsteady flow characteristics. Numerical model of drifting cup is introduced to investigate an interaction between flow and
motion of the cup. Finally, the intention of the channel design is interpreted from the viewpoint of fluid mechanics using
observed and calculated results. 相似文献