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21.
Tatsuro Ouchi Hiroshi Sakamoto Yoshifumi Hosaka Minoru Imoto Tsutomu Iwamoto 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1025-1038
Abstract The polymerization of some kinds of vinyl monomer was found to occur without an ordinary initiator in aqueous solutions of AB-type block or random copolymers of sodium methacrylate with styrene as a so-called “uncatalyzed polymerization.” Although the spin trapping technique showed that the initiation mechanism by the block copolymer was the same as that by the random copolymer, the initiating ability of the block copolymer was lower than that of the random copolymer. Such results are attributable to the difference in the incorporating ability of monomer into the micelles formed by the block copolymer and into the hydrophobic areas formed by the random copolymer. 相似文献
22.
Tatsuro Ouchi Hiroshi Sakamoto Masayasu Kubo Yoshifumi Hosaka Minoru Imoto 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):111-123
The radical polymerization of vinyl monomers initiated with several kinds of hydrophilic macromolecule was carried out in a magnetic field. The magnetic field promoted the polymerization; the conversion of monomers and the molecular weight of the polymers obtained increased with increasing field strength in the range of 0–0.1 T. The dependence of the composition and tacticity of the mother polymer on the magnitude of the magnetic field was studied. Using graft or block copolymers, which consisted of hard and soft segments, the effect of a magnetic field was further investigated. The degree of hardness and tightness of the hydrophobic areas (reaction areas) formed by the mother polymer in the aqueous solution was found to affect the magnetic field effect on the uncatalyzed polymerization. The overall activation energy obtained in the magnetic field was almost equal to that obtained without a magnetic field. 相似文献
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Dr. Ryo Tsunashima Yoshifumi Iwamoto Yusuke Baba Chisato Kato Katsuya Ichihashi Dr. Sadafumi Nishihara Prof. Katsuya Inoue Prof. Katsuya Ishiguro Prof. Yu‐Fei Song Prof. Tomoyuki Akutagawa 《Angewandte Chemie (International ed. in English)》2014,53(42):11228-11231
In a mixed‐valence polyoxometalate, electrons are usually delocalized within the cluster anion because of low level of inter‐cluster interaction. Herein, we report the structure and electrical properties of a single crystal in which mixed‐valence polyoxometalates were electrically wired by cationic π‐molecules of tetrathiafulvalene substituted with pyridinium. Electron‐transport characteristics are suggested to represent electron hopping through strong interactions between cluster and cationic π‐molecules. 相似文献
25.
Mechanism of Back Electron Transfer in an Intermolecular Photoinduced Electron Transfer Reaction: Solvent as a Charge Mediator 下载免费PDF全文
Sudhakar Narra Dr. Yoshifumi Nishimura Prof. Dr. Henryk A. Witek Prof. Dr. Shinsuke Shigeto 《Chemphyschem》2014,15(14):2945-2950
Back electron transfer (BET) is one of the important processes that govern the decay of generated ion pairs in intermolecular photoinduced electron transfer reactions. Unfortunately, a detailed mechanism of BET reactions remains largely unknown in spite of their importance for the development of molecular photovoltaic structures. Here, we examine the BET reaction of pyrene (Py) and 1,4‐dicyanobenzene (DCB) in acetonitrile (ACN) by using time‐resolved near‐ and mid‐IR spectroscopy. The Py dimer radical cation (Py2.+) and DCB radical anion (DCB.?) generated after photoexcitation of Py show asynchronous decay kinetics. To account for this observation, we propose a reaction mechanism that involves electron transfer from DCB.? to the solvent and charge recombination between the resulting ACN dimer anion and Py2.+. The unique role of ACN as a charge mediator revealed herein could have implications for strategies that retard charge recombination in dye‐sensitized solar cells. 相似文献
26.
Dr. Yoshifumi Hashikawa Hui Li Prof. Dr. Yasujiro Murata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(27):7507-7511
Cage-opened bisfulleroids are one of suitable building blocks for making a large hole on fullerenes. This work focuses on the Diels-Alder reaction of C60 with azines, among synthetic methods developed thus far, to provide bisfulleroids. Surprisingly, the computational study predicted that the reaction proceeds with normal electron demand in contrast to hitherto considered inverse-electron-demand pathway. The benzoannulation to the pyridazine ring, i. e., phthalazine, resulted in the remarkably shortened reaction time due to the better interaction between the HOMO of phthalazine and the LUMO of C60 as well as stronger 2,3-diaza-1,3-butadiene character in the phthalazine as confirmed crystallographically. Contrary to expectations, the benzobisfulleroid was converted into corresponding orifice-enlarged derivative via the photooxygenation slightly faster than the fulleroid derived from pyridazine. 相似文献
27.
Sako M Kihara T Tanisaki M Maki Y Miyamae A Azuma T Kohda S Masugi T 《The Journal of organic chemistry》2002,67(3):668-673
The UV irradiation of pyrrolnitrin (1a), which is an antibiotic clinically useful against dermatophytosis and possesses a unique 2-(pyrrol-3-yl)nitrobenzene moiety in the molecule, in an anhydrous aprotic solvent resulted in the exclusive formation of transient 7,4'-dichlorospiro[1,3-dihydrobenzo(c)isoxazole-3,3'-pyrrolin-2'-one] (2a) via the intramolecular oxidation of the juxtaposed pyrrole ring by the triplet-excited nitro group. The irradiation in an aqueous aprotic solvent, however, allowed the concurrent occurrence of intramolecular cyclization by the singlet-excited nitro group in 1a and the hydroxylation at the 2-position of the pyrrole ring by water to afford 3,7-dichloro-8-hydroxy-8,8a-dihydropyrrolo[2,3-b]indol-2-one (3a), accompanied by the formation of 2a. Elongation of the irradiation time in these photoreactions caused a rapid consumption of the products, 2a and 3a, to give undetermined polar polymeric products. The present results indicate that the photodegradation of 1a is significantly influenced by the presence of water in the reaction media and by the nature of its excited state. Thus, the loss of the antifungal activities by the photosensitive antibiotic 1a was chemically proved. 相似文献
28.
Haino T Araki H Fujiwara Y Tanimoto Y Fukazawa Y 《Chemical communications (Cambridge, England)》2002,(18):2148-2149
A new class of fullerene sensors based on calix[5]arenes has produced the highly sensitive detection of C60 and C70. 相似文献
29.
Yasuto Uchio Junzo Toyota Hiroshi Nozaki Mitsuru Nakayama Yoshifumi Nishizono Tsunao Hase 《Tetrahedron letters》1981,22(41):4089-4092
The structures of lobohedleolide (1) and (7Z)-lobohedleolide (2), two new cembranolides containing the α,β-unsaturated carboxylic acid system isolated from the Japanese soft coral Lobophytum hedleyi Whitelegge, were elucidated from spectral and chemical evidence, and the absolute configuration of (1) was determined by X-ray analysis of its p-bromophenacyl ester (9). Lobohedleolide (1) showed growth inhibition of the in vitro Hella cells. 相似文献
30.