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Kaieda T Kobatake S Miyasaka H Murakami M Iwai N Nagata Y Itaya A Irie M 《Journal of the American Chemical Society》2002,124(9):2015-2024
Multi-dithienylethene arrays, in which two, three, or four 1,2-bis(2,4-dimethylthiophen-3-yl)perfluorocyclopentenes are ethynylene-bridged, were synthesized. Upon irradiation with ultraviolet light the hexane solutions of the arrays turned violet-blue and the color disappeared by irradiation with visible light. The quantum yields of photocyclization reactions successively increased from 0.21 to 0.40 by increasing the number of the dithienylethene moieties in the arrays from one to four. Picosecond laser photolysis as well as the fluorescence depolarization experiment confirmed that efficient excited energy migration in the arrays from the photochemically inactive parallel conformer to the photoactive antiparallel conformer resulted in the high quantum yields. 相似文献
87.
Tomoyuki Itaya Hiroshi Ochiai Tsuyoshi Aoyama Kazuyoshi Ueda Akira Imamura 《Journal of Polymer Science.Polymer Physics》1994,32(1):171-177
The hydrophobic association behavior of p-propylbenzenesulfonate ions (n-PBS? and iso-PBS?) around poly(allylammonium) cation (PAAH+ was studied by absorption and 1H nuclear magnetic resonance (NMR) spectroscopy. In the presence of PAAH+Cl?, the broadening (hypochromism) of absorption band of PBS? were observed. In addition, all 1H NMR signals of PBS? exhibited up-field shift which resulted from the intermolecular ring current shift. These results indicate the hydrophobic association of negative PBS? around PAAH+. The hydrophobic association arises from the accumulation of counterions around the polyion, and is stabilized by the hydrophobic interaction between propyl groups and the stacking interaction between benzene rings. The association of iso-PBS? ions is rather weaker than that of n-PBS?, suggesting that the steric hindrance of isopropyl groups prevents an effective association of hydrophobic counterions. Furthermore, through viscosity and Cl? activity measurements, it was found that the binding of associated PBS?,s to PAAH+ causes the change of its surroundings to hydrophobic character and its conformation. © 1994 John Wiley & Sons, Inc. 相似文献
88.
Acid- or base-catalyzed acylation of 1-benzylwye (7) provided the 7-substituted derivatives 9, 10, and 11 in poor yields. Although the reactions of lithiated 7 with electrophiles gave the 2-substituted derivatives 14, 15, 17, 20, 21, and 22, lithiation of 1-benzyl-7-bromo-2-chlorowye (23) followed by treatment with Me2CHCH2CHO (13) successfully introduced a side chain at the 7-position to afford 1-benzyl-2-chloro-7-(1-hydroxy-3-methylbutyl)wye (24). Cyclization of 1-benzyl-3-methylguanine (5) with 3-bromo-2-butanone followed by catalytic hydrogenolysis afforded 7-methylwye (2b), the hypermodified base isolated from archaebacterial transfer ribonucleic acids. A more efficient route for the synthesis of 2b has been developed via a series of reactions: the Vilsmeier-Haack reaction of 7, reduction with NaBH4, and catalytic hydrogenolysis over Pd-C. 相似文献
89.
Yoshimoto S Tsutsumi E Fujii O Narita R Itaya K 《Chemical communications (Cambridge, England)》2005,(9):1188-1190
Supramolecularly assembled layers of C60 on coronene- and perylene-modified Au(111) surfaces were investigated and the structure of the C60 adlayer was found to be strongly influenced by the underlying organic layers, suggesting that the latter underlying organic adlayers play an important role in the process of formation of the C60 molecular adlayer. 相似文献
90.
Uchida K Sukata S Matsuzawa Y Akazawa M de Jong JJ Katsonis N Kojima Y Nakamura S Areephong J Meetsma A Feringa BL 《Chemical communications (Cambridge, England)》2008,(3):326-328
Dithienylhexafluorocyclopentene with (R)- or (S)-N-phenylethylamide substituents formed rod-like and 0.2-1.0 microm-thick platelike crystals by sublimation; upon UV irradiation, the crystals bent concavely to the incident light and finally rolled crystals were obtained; the bent crystals were reconverted to flat crystals by visible light irradiation. 相似文献