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排序方式: 共有168条查询结果,搜索用时 15 毫秒
161.
Asami Yoshii Yuzuka Onaka Koki Ikemoto Tomoo Izumi Sota Sato Hiroshi Kita Hideo Taka Hiroyuki Isobe 《化学:亚洲杂志》2020,15(14):2181-2186
Oligo‐meta‐phenylenes have been designed and synthesized as multipotent base materials of single‐layer organic light‐emitting devices. Simple molecular structures of oligo‐meta‐phenylenes composed of linear phenylene arrays benefited from the wealth of modern reactions available for biaryl couplings and were concisely synthesized in a series. Structure‐performance relationship studies with the first seven congeners revealed key features important for the multipotent materials in single‐layer devices. As a result, highly efficient phosphorescent electroluminescence was made possible in a highly simplified device architecture comprising one‐region, single‐layer configurations. Detailed investigations with hole‐only devices disclosed that the hole mobility was effectively retarded by potent materials, which should facilitate hole/electron recombination for electroluminescence. 相似文献
162.
Kiyota N Shingu K Yamaguchi K Yoshitake Y Harano K Yoshimitsu H Ikeda T Nohara T 《Chemical & pharmaceutical bulletin》2007,55(1):34-36
Three new C(28) steroidal glycosides, isotubocaposides A (1), B (2), and C (3), were isolated from the fruits of Tubocapsicum anomalum MAKINO. Their chemical structures were elucidated on the basis of spectroscopic and X-ray diffraction analysis of p-bromobenzoyl derivative (5) of isotubocaposigenin (4), the sapogenol derivative of these three glycosides. Isotubocaposides have the structural peculiarity of an unusual side chain carrying a C-21 bound to C-24 on the lactone ring. 相似文献
163.
In the pore of a porous coordination network, Diels-Alder reactants, a diene and a dienophile, are recognized by donor-acceptor and multiple H-bond interactions, respectively, and fixed at ideal positions for the reaction. Heating the crystals promoted the Diels-Alder reactions with enhanced reactivity and controlled regioselectivity as clearly monitored by in situ X-ray crystallography. 相似文献
164.
Yamaguchi S Kobayashi H Narita T Kanehira K Sonezaki S Kudo N Kubota Y Terasaka S Houkin K 《Ultrasonics sonochemistry》2011,18(5):1197-1204
Sonodynamic therapy is expected to be a novel therapeutic strategy for malignant gliomas. The titanium dioxide (TiO(2)) nanoparticle, a photosensitizer, can be activated by ultrasound. In this study, by using water-dispersed TiO(2) nanoparticles, an in vitro comparison was made between the photodynamic and sonodynamic damages on U251 human glioblastoma cell lines. Water-dispersed TiO(2) nanoparticles were constructed by the adsorption of chemically modified polyethylene glycole (PEG) on the TiO(2) surface (TiO(2)/PEG). To evaluate cytotoxicity, U251 monolayer cells were incubated in culture medium including 100 μg/ml of TiO(2)/PEG for 3h and subsequently irradiated by ultraviolet light (5.0 mW/cm(2)) or 1.0MHz ultrasound (1.0 W/cm(2)). Cell survival was estimated by MTT assay 24h after irradiation. In the presence of TiO(2)/PEG, the photodynamic cytotoxic effect was not observed after 20 min of an ultraviolet light exposure, while the sonodynamic cytotoxicity effect was almost proportional to the time of sonication. In addition, photodynamic cytotoxicity of TiO(2)/PEG was almost completely inhibited by radical scavenger, while suppression of the sonodynamic cytotoxic effect was not significant. Results of various fluorescent stains showed that ultrasound-treated cells lost their viability immediately after irradiation, and cell membranes were especially damaged in comparison with ultraviolet-treated cells. These findings showed a potential application of TiO(2)/PEG to sonodynamic therapy as a new treatment of malignant gliomas and suggested that the mechanism of TiO(2)/PEG mediated sonodynamic cytotoxicity differs from that of photodynamic cytotoxicity. 相似文献
165.
Magnetic measurements were made using pure YBCO and Zn doped YBa2(Cu1?xZnx)3O7?σ. Single crystals with Zn concentration of 0.5%, 1.5%, 3.0% and 4.3%. The magnetic hysteresis loops for these samples were measured in the temperature range 0.1 ? T/Tc ? 0.96 under magnetic fields of 5 T using SQUID. It was found that the critical current density Jc increased for low Zn content samples up to 3% Zn concentration compared to pure YBCO sample and decreased for the higher Zn content samples. These values varied consistently when compared at magnetic fields of 1 T and 3 T. Moreover Zn doped samples showed significant values of Jc in the temperature range of 0.7–0.9Tc, close to critical temperature compared to pure YBCO sample. The irreversibility field Hirr was also enhanced in this temperature range showing consistent decrease with increase of Zn concentration. The peak field Hp above Hc1 and irreversibility field Hirr, both show power law dependence of the form H = m1(1 ? T/Tc)m2 in the temperature range of 0.75–0.96Tc. The values of parameter m2 increased from 1.44 to 1.95 for the samples up to 3% Zn content and decreased to 1.37 for higher Zn contents. The ratio Hirr/Hp was found to be 3–4 for the lower Zn content samples and was 7–8 for the sample with high Zn content indicating more disorder for higher Zn content samples. The region between peak field Hp and irreversibility field Hirr was broadened with the increase of Zn concentration. The strong effect of Zn substitution in modifying behavior of these samples even at elevated temperatures is possibly due to the changes in the anisotropy of our samples with the increase of Zn concentration and also due to the locally induced changes in magnetic moments by Zn substitution. 相似文献
166.
Koki Fujimura Dr. Yoshihiro Ueda Dr. Yousuke Yamaoka Prof. Kiyosei Takasu Prof. Takeo Kawabata 《Angewandte Chemie (International ed. in English)》2023,62(30):e202303078
A method for rotaxane synthesis by enlargement of the size of the terminal phenol group of the axle component by aromatic bromination has been developed. This method may be regarded as an end-capping strategy involving the swelling of the phenol group at the axle terminal. The advantages of the present strategy include: ready availability of axle components with a variety of swelling precursors, wide product scope (19 examples given including a [3]rotaxane), mild conditions for the swelling process, rich potential for the derivatization of the brominated rotaxanes, and possible release of the axle component by degradative dethreading of the thermally stable brominated rotaxanes under the basic conditions. 相似文献
167.
Dr. Koki Ikemoto Kanato Takahashi Prof. Dr. Takeaki Ozawa Prof. Dr. Hiroyuki Isobe 《Angewandte Chemie (International ed. in English)》2023,62(14):e202219059
“How do we decide the stoichiometry of host–guest complexes?” This question has long been answered by the Job plot since its first report in 1928. However, as the Job plot was claimed to be misleading in 2016, the question became an open question again and called for renewed investigations. An information-theoretic approach, called Akaike's information criterion, is introduced in this study to select the best model of host–guest complexes, which can rank the models with weight of evidence. A few test cases with unique cylindrical hosts were examined to demonstrate the applicability of the information-theoretic method. Consequently, reasonable views over the thermodynamic behaviors of dumbbell-and-cylinder complexes were obtained. Akaike's information criterion can be a useful and superior alternative to statistical null hypothesis testing, which was proposed as a remedy in place of the Job plot. 相似文献
168.
Koki Yoshizawa Dr. Keisuke Hirata Prof. Shun-ichi Ishiuchi Prof. Masaaki Fujii Dr. Anne Zehnacker 《Chemphyschem》2023,24(18):e202300172
Alkali metal complexes of cyclic dipeptide cyclo Tyr-Tyr have been studied under cryogenic ion trap conditions. Their structure was obtained by combining Infra-Red Photo-Dissociation (IRPD) and quantum chemical calculations. The structural motif strongly depends on the relative chirality of the tyrosine residues. For residues of identical chirality, the cation interacts with one amide oxygen and one of the aromatic rings only; the distance between the aromatic rings does not change with the nature of the metal. In contrast, for residues of opposite chirality, the metal cation is located in between the two aromatic rings and interacts with both of them. The distance between the two aromatic rings strongly depends on the metal. Electronic spectra obtained by Ultra Violet Photodissociation (UVPD) spectroscopy and analysis of the UV photo-fragments shed light on the excited state deactivation processes, which depend on both the chirality of the residue and that of the metal ion core. Na+ stands out by the presence of low-lying charge transfer states resulting in the broadening of the electronic spectrum. 相似文献