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排序方式: 共有341条查询结果,搜索用时 15 毫秒
91.
Haino T Kobayashi M Fukazawa Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(12):3310-3319
The synthesis and spectroscopic characterization of a cavitand-based coordination capsule 14 BF4 of nanometer dimensions is described. Encapsulation studies of large aromatic guests as well as aliphatic guests were performed by using 1H NMR spectroscopy in [D1]chloroform. In addition to the computational analysis of the shape and geometry of the capsule, an experimental approach to estimate the interior size of the cavity is discussed. The cavity provides a highly rigid binding space in which molecules with lengths of approximately 14 A can be selectively accommodated. The rigid cavity distinguished slight structural differences in the flexible alkyl-chain guests as well as the rigid aromatic guests. The detailed thermodynamic studies revealed that not only CH-pi interactions between the methyl groups on the guest termini and the aromatic cavity walls, but also desolvation of the inner cavity play a key role in the guest encapsulation. The cavity preferentially selected the hydrogen-bonded heterodimers of a mixture of two or three carboxylic acids 18-20. The chiral capsule encapsulated a chiral guest to show diastereoselection. 相似文献
92.
Mitsushiro Nomura Souichi Sakaki Yoshimasa Hoshino 《Journal of organometallic chemistry》2006,691(15):3274-3284
The one-pot reaction of [Cp∗Mo(NO)(CO)2] with elemental sulfur and dimethyl acetylenedicarboxylate (C2Z2 (Z = COOMe)) gave the [2+2] cycloadduct of the mononuclear molybdenum dithiolene complex [Cp∗Mo(NO)(S2C2Z2)(C2Z2)] (1), and some binuclear complexes:[Cp∗Mo(NO)(S2C2Z2)]2 (2), [Cp∗2Mo2(NO)2S2(S2C2Z2)] (3) and [Cp∗Mo(NO)S2]2 (4).The reaction of [Cp∗Mo(NO)(Cl)(μ-Cl)]2 with OC{S2C2(COOMe)2} in the presence of sodium methoxide also produced complex 2 and the paramagnetic Cp∗Mo bisdithiolene complex [Cp∗Mo(S2C2Z2)2] (5, Z = COOMe).The structures of complexes 1-5 were determined by X-ray crystal structure analysis.The nitrosyl ligands of complexes 1-4 showed a linear coordination to the molybdenum center (the Mo-N-O bond angles = 169-174°), and their N-O bond lengths were 1.17-1.20 Å.In the binuclear complexes 2-4, two nitrosyl ligands were placed at cis-position.Complexes 1 and 2 were characterized by cyclic voltammetry and spectroelectrochemistry (visible and IR). The electrochemical reduction of the dimeric complex 2 formed the monomeric dithiolene complex[Cp∗Mo(NO)(S2C2Z2)]− (X−) whose lifetime was several minutes. When the anion X− was electrochemically oxidized, the coordinatively unsaturated species X was generated, but it was immediately dimerized to afford the original dimeric complex 2. The reduction of the complex 1 included the elimination of the bridged DMAD moiety (C2Z2) to give the anion X−. 相似文献
93.
The first method for cyano-phosphorylation of aldehydes with diethyl cyanophosphonate in the presence of N-heterocyclic carbene prepared from 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride and KOt-Bu, as a nucleophilic catalyst, is described. 相似文献
94.
Motomasa Kobayashi Byeng Wha Son Takaji Fujiwara Yoshimasa Kyogoku Isao Kitagawa 《Tetrahedron letters》1984,25(48):5543-5546
A new diterpene named neodolabelline (5), having a methyl migrated dolabellane-type skeleton, was isolated from the stoloniferan soft coral Clavularia koellikeri, together with clavukerins (trinor-sesquiterpenes) and bicyclo-germacrene, and the absolute configuration was determined. 相似文献
95.
A bridged triptycene was obtained by intramolecular cycloaddition reaction of 16,19-dimethoxy[2](9,10)anthraceno[2]paracyclophane followed by acid-catalyzed elimination of methanol. Internal strain in this molecule was disclosed by X-ray crystallographic analysis. 相似文献
96.
Motomasa Kobayashi Yutaka Kiyota Satomi Orito Yoshimasa Kyogoku Isao Kitagawa 《Tetrahedron letters》1984,25(34):3731-3734
Five new pregnene-type steroidal glycosides, named pregnedioside -a (), 4′-O-acetyl-pregnedioside-a (), 3′-O-acetyl-pregnedioside-a (), pregnedioside-b (), and 4′-O-acetyl-pregnedioside-b (), were isolated from an Okinawan soft coral of Alcyonium sp. and their structures were elucidated. These are rare examples of steroidal gylcosides from soft coral. 相似文献
97.
Tetsuaki Nishida Yoshimasa Takashima Yusuke Nakayama 《Journal of solid state chemistry》1980,33(2):141-144
Potassium borate glasses denoted by the formula xK2O · (100 ? x)B2O3 · 7Fe2O3 were irradiated with 60Co-γ-rays at room temperature. Mössbauer parameters for the irradiated glasses containing alkali equal to or higher than 20 mole% showed that the s-electron density at the iron nucleus increased without any change of the steric configuration of oxygen atoms around the iron nucleus. The increase of s-electron density was ascribed to electron transfer from the nonbridging oxygen to the iron nucleus. The presence of the nonbridging oxygen was also confirmed by the irradiation effect of the borate glass (x = 30) prepared using the enriched isotope of 57Fe2O3. Mössbauer parameters for the irradiated glass suggest that the newly observed Fe2+ ions are in tetrahedral symmetry. 相似文献
98.
Toshitami Ooi Koji Mimura Yoshimasa Hama Kenichi Shinohara 《Journal of polymer science. Part A, Polymer chemistry》1976,14(4):813-824
Paramagnetic species produced in a series of linear aliphatic oligoesters $ [\bond;{\rm O}\bond;({\rm CH}_{\rm 2} {\rm )}_m\bond;{\rm O}\bond;{\rm CO}\bond;({\rm CH}_{\rm 2} {\rm )}_n\bond;{\rm CO\rlap{--} ]}_P $ by γ-irradiation at 77°K was investigated by an ESR method. A predominant doublet observed immediately after γ-irradiation, which has hyperfine splitting of 20–23 gauss, is attributed to a radical anion III. Slight decay of this radical anion is observed by illuminating the sample with visible light at 77°K. A small amount of the radical anion is converted to double triplet, which is assigned to ? (ES)? CH? CH2? (where ES denotes the ester group), from the result of heat treatment. The conformational angles for the two β-protons in the (6,2) oligoester are determined to be θ1 = θ2 = 30°. 相似文献
99.
Nano-matrix structure formed by graft-copolymerization of styrene onto natural rubber 总被引:1,自引:0,他引:1
Nanthaporn Pukkate Yoshimasa Yamamoto Jitladda Sakdapipanich 《European Polymer Journal》2007,43(8):3208-3214
Nano-matrix structure was formed by graft-copolymerization of styrene onto urea-deproteinized natural rubber (U-DPNR) latex. The grafted U-DPNR was characterized by FT-IR spectroscopy, 1H NMR spectroscopy and transmission electron microscopy. Conversion and grafting efficiency of styrene were more than 90% under the best condition of the graft-copolymerization. In transmission electron micrograph of film specimen stained by OsO4, it was found that natural rubber particle of about 0.5 μm in diameter was dispersed in polystyrene matrix of about 15 nm in thickness. The conversion and grafting efficiency for the grafted U-DPNR were compared with those for a control sample prepared from enzymatic deproteinized natural rubber (E-DPNR) with styrene. 相似文献
100.
Mikio Hoshino Hiroshi Seki Minoru Yamaji Yoshimasa Hama 《Photochemistry and photobiology》1993,57(4):728-731
Abstract— Photochemistry of superoxide adducts of cobalt(II) and zinc(II) porphyrins has been studied by laser photolysis. It was found that the former in dimethlformamide photodissociates the superoxide anion radical, O2 - , with the quantum yield of 0.5 ± 0.05 at the excitation wavelenths 355 and 532 nm, and the latter gives flurescence and the triple state without giving rise to the photodissociation of O2 - 相似文献