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51.
Tsukasa Nakahodo Midori O. Ishitsuka Yutaka Maeda Hisashi Fujihara Takeshi Akasaka 《Tetrahedron letters》2008,49(14):2302-2305
The photochemical reaction of C60 with selenium-containing bicyclooctanes affords for the first time the selenylfullerenes. The derivatives were characterized by mass, UV-vis absorption, NMR spectroscopy, and X-ray crystallographic analysis. 相似文献
52.
Yuri Saito Dr. Jun Kikuchi Prof. Chen Wang Prof. Naohiko Yoshikai 《Angewandte Chemie (International ed. in English)》2023,62(17):e202301006
We report herein the design and development of Co/Al and Co/Mg bimetallic catalysts, supported by a phosphine/secondary phosphine oxide (PSPO) bifunctional ligand, for the site-selective C−H alkenylation of nitrogen-containing heteroarenes with alkynes. These catalysts enable the alkenylation of pyridine, pyridone, and imidazo[1,2-a]pyridine derivatives at the C−H site proximal to the Lewis basic nitrogen or oxygen atom, which represents a selectivity profile distinct from that of the previously developed cobalt-diphosphine/aluminum catalyst. The alkenylated products were obtained in moderate to good yields using various heterocycles and differently substituted internal alkynes. Kinetic isotope effect experiments suggest the irreversibility of the C−H activation step, the relevance of which to the rate-limiting step depends on the reaction conditions. Density functional theory calculations indicate that ligand-to-ligand hydrogen transfer is the common mechanism of C−H activation. 相似文献
53.
Otsuki J Imai A Sato K Li DM Hosoda M Owa M Akasaka T Yoshikawa I Araki K Suenobu T Fukuzumi S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(9):2709-2718
A star-shaped Ru/Os tetranuclear complex, in which a central Os unit is linked to three peripheral Ru units by 4,4'-azobis(2,2'-bipyridine) (azobpy) bridging ligands, was prepared to examine the unique photodynamics regulated by its redox state. The Ru/Os tetranuclear complex exhibits Ru-based luminescence at 77 K, whereas the three-electron reduction (one for each azobpy) of the Ru/Os complex results in luminescence from the Os unit. The photoexcited state of the Ru/Os complex rapidly decays into low energy metal-to-ligand charge-transfer states, in which the excited electron is localized in the azobpy ligand in the form of azobpy(.-). Upon the one-electron reduction of the azobpy ligands, the above-mentioned low-energy states become unavailable to the photoexcited complex. As a result, an energy transfer from the Ru-based excited state to the Os-based excited state becomes possible. Ultrafast transient absorption measurements revealed that the energy transfer process consists of two steps; intramolecular electron transfer from the terminal bipyridine ligand (bpy(.-)) to form azobpy(2-) followed by a metal-to-metal electron transfer. Thus, the Ru/Os tetranuclear complex collects light energy into the central Os unit depending on the redox state of the bridging ligands, qualifying as a switchable antenna. 相似文献
54.
Watanabe K Makino R Takahashi H Iguchi K Ohrui H Akasaka K 《Chemical & pharmaceutical bulletin》2008,56(6):861-863
A new unsaturated fatty acid with unique vicinal dimethyl branches was isolated from the Okinawan soft coral of the genus Sinularia. The structure of the compound was determined based on the results of spectroscopic analysis and chemical conversion. The absolute configuration was deduced by applying the Ohrui-Akasaka method. 相似文献
55.
Isolation and Crystallographic Characterization of the Labile Isomer of Y@C82 Cocrystallized with Ni(OEP): Unprecedented Dimerization of Pristine Metallofullerenes
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Lipiao Bao Changwang Pan Prof. Zdenek Slanina Prof. Filip Uhlik Prof. Takeshi Akasaka Prof. Xing Lu 《Angewandte Chemie (International ed. in English)》2016,55(32):9234-9238
Although the major isomers of M@C82 (namely M@C2v(9)‐C82, where M is a trivalent rare‐earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C82 isomer, unambiguously assigned as Y@Cs(6)‐C82 by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@Cs(6)‐C82. In sharp contrast, no dimerization occurs for the major isomer Y@C2v(9)‐C82 under the same conditions, indicating a cage‐symmetry‐induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage‐carbon atom of Y@Cs(6)‐C82 which is caused by the steady displacement of the Y atom inside the Cs(6)‐C82 cage. 相似文献
56.
Ikeda M Minari J Shimada N Numata M Sakurai K Shinkai S 《Organic & biomolecular chemistry》2007,5(14):2219-2224
A cationic polysaccharide bearing a beta-1,3-glucan main-chain structure (CUR-N(+)) forms a complex with a hetero-sequence oligonucleotide, that is, a CpG ODN, and facilitates the transportation of the resultant complex into a murine macrophage-like cell J774.A1, which induces an efficient secretion of a cytokine (IL-12) as compared with that induced by conventional carriers such as poly(ethyleneimine) (PEI) and poly(L-lysine) (PLL). 相似文献
57.
58.
Morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA)/toluene droplets, in which phase separation proceeds, dispersed in SDS aqueous solution was examined. It changed from ex-centered PS-core/PMMA-shell to hemisphere with increasing SDS concentration. At low polymer weight fraction (wp), PS and PMMA phases contained non-negligible amount of PMMA and PS, respectively. The small amount of PS and PMMA in PMMA and PS phases, respectively, affected significantly the interfacial tension between polymer/toluene and aqueous solutions. Interfacial tension between PS and PMMA phases at low wp was measured by the spinning drop method, showing a quite low value ( approximately 10-2 mN/m). Predicted morphology obtained from calculation of minimum total interfacial free energy of the droplets using the interfacial tensions agreed well with the experimental observation. 相似文献
59.
Shigeru Nagase Kaoru Kobayashi Takeshi Akasaka 《Journal of computational chemistry》1998,19(2):232-239
The structural determination of endohedral metallofullerenes has attracted special attention in disclosing the formation mechanism and developing new routes to bulk production. Recent advances in the theoretical and experimental studies are summarized with representative mono- and dimetallofullerenes such as M@C82 (M=Ca, Sc, Y, and La), Sc2@C84, and La2@C80. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 232–239, 1998 相似文献