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168 results on '"Kubo, Yasuo"'

7. A novel 1,8-photoaddition of dimethyl 1,4-naphthalenedicarboxylate to alkenes

Author

Kubo, Yasuo, Inoue, Takeo, and Sakai, Hidefusa

Subjects
Chemical reactions -- Research, Naphthalene -- Research, Olefins -- Research, Irradiation -- Usage, Chemistry
Abstract

The 1,8-photoaddition of dimethyl 1,4-naphthalenedicarboxylate to alkenes proceeds stereospecifically with the generation of a zwitterionic intermediate. The irradiation of dimethyl 1,4-naphthalenedicarboxylate in the presence of isobutene in ether yields 1,8-adducts. The photoaddition is also possible in benzene and acetonitrile. The 1,8-addition arises from the singlet excited state of the dicarboxylate, since there is no evidence for a ground-state complex between the dicarboxylate and the alkenes.

Published
1992

10. Control of photophysical properties and photoreactions of aromatic imides by use of intermolecular hydrogen bonding

Author

Matsubayashi, Kazuhiko and Kubo, Yasuo

Subjects
Alcohols -- Chemical properties, Amides -- Chemical properties, Hydrogen bonding -- Analysis, Photochemistry -- Research, Biological sciences, Chemistry
Abstract

A study was conducted to determine the effect of alcohol addition and the intermolecular hydrogen bonding on the photophysics and photoreactions of aromatic imide compounds. The results showed that the photophysical properties and the photoreactivity of aromatic imides could be controlled by simple addition of alcohol.

Published
2008

44. Control of Photophysical Properties of 1,8-Naphthalimides by Electron-Withdrawing Substituents Introduced into N-Alkyl Side Chains

Author

Matsubayashi, Kazuhiko, Kajimura, Chisato, Kubo, Yasuo, Yoshihara, Toshitada, and Tobita, Seiji

Abstract

The fluorescence intensity of naphthalimides 1–7in dichloromethane was found to be remarkably enhanced by the introduction of an electron-withdrawing substituent, such as OCOMe, CO2Me, Cl, and CN, into the N-alkyl side chain. The rate constants of the fluorescence emission kf, the intersystem crossing kisc, and the internal conversion kicfor 1–7in dichloromethane and in acetonitrile were determined based on the measurements of the fluorescence lifetimes tf, by using picosecond single photon counting, and the quantum yields of the intersystem crossing Fiscdetermined by time-resolved thermal lensing. These results indicate that the value of kiscdecreases with an increase in the electron-withdrawing ability of the substituent. Furthermore, an almost linear Hammett relationship (? = -1.48 in dichloromethane, ? = -1.85 in acetonitrile) between the logarithm of kiscand the substituent constant sIfor inductive effect of the substituent through the s bond was observed. The enhancement of the fluorescence intensity by the introduction of electron-withdrawing substituents was thus explained by a decrease in the efficiency of the intersystem crossing from 1(pp*) to 3(np*), whose energy was increased by the inductive effect of the substituent through the s bonds.

Published
2011
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50. Kinetic Analysis for the Effect of Intramolecular Hydrogen Bonding on Photophysical Properties of N-Hydroxyalkyl-1,8-naphthalimides

Author

Matsubayashi, Kazuhiko, Kajimura, Chisato, Shiratori, Hideo, Kubo, Yasuo, Yoshihara, Toshitada, and Tobita, Seiji

Abstract

N-Methyl-, N-(2-hydroxyethyl)-, N-(2-methoxyethyl)-, N-(3-hydroxypropyl)-, and N-(3-methoxypropyl)-1,8-naphthalimide (1, 2a, 2b, 3a, and 3b, respectively) were prepared and their photophysical properties examined. The UV and IR spectra of 2aand 3ain dichloromethane showed the presence of intramolecular hydrogen bonding between the carbonyl group and the hydroxy group. In addition, the fluorescence intensities of 2aand 3ain dichloromethane were found to be about two times larger than those of 1, 2b, and 3b. Furthermore, the fluorescence lifetimes of 2aand 3a, determined by picosecond single photon counting, were about two times longer than those of 1, 2b, and 3b. The rate constants of the intersystem crossing (kisc) for 2aand 3a, calculated based on the quantum yields of the intersystem crossing (Fisc) determined by the time-resolved thermal lensing technique, were about one half of those obtained for 1, 2b, and 3b, while the rate constants of fluorescence emission (kf) and internal conversion (kic) were minimally affected by the presence of intramolecular hydrogen bonding. Enhancement of the fluorescence quantum yield and the lifetime of 2aand 3awas thus explained by a decrease in the efficiency of the intersystem crossing from 1(pp*) to 3(np*), that results from an increase in the energy of the 3(np*) level due to the presence of intramolecular hydrogen bonding.

Published
2010
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