- Water-induced fluorescence quenching of mono- and dicyanoanilines
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Photophysical properties of monocyano- (2-, 3-, and 4-cyano) and dicyano- (3,4-, 3,5-, 2,3-, 2,4-, 2,5-, and 2,6-dicyano) anilines are investigated by fluorescence measurements. All the monocyanoanilines are virtually nonfluorescent in water (quantum yield 0.01); however, in nonaqueous solvents (cyclohexane, acetonitrile and ethanol), the fluorescence quantum yield is enhanced substantially. In contrast, dicyanoanilines investigated are highly fluorescent both in aqueous and nonaqueous environments. The photophysical data and MO calculations suggest that conformational changes in the amino group and variation of hydrogen-bonding interactions between the solute and solvent water upon electronic excitation are responsible for the water quenching in the monocyanoanilines.
- Oshima, Juro,Yoshihara, Toshitada,Tobita, Seiji
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p. 306 - 311
(2008/02/13)
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- Evidence for Homo-Conjugation between Two Revolving 14π-Electron Systems in 10b-Methyl-10c-[2-(10b,10c-dimethyl-10b,10c-dihydropyrenyl)]-10b, 10c-dihydropyrene
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Ring contraction followed by an elimination reaction on anti-9-methyl-18-trans-2-(10b,10c-dimethyl-10b,10c-dihydropyrenyl)-2,11-dithia[3,3]metacyclophane gave the desired compound 10b-methyl-10c-[2-(10b,10c-dimethyl-10b,10c-dihydropyrenyl)]-10b,10c-dihydropyrene. 1H NMR spectroscopic analysis indicated a ring current effect over a considerable distance from the macro-molecular plane of each of the aromatic rings with the two π systems freely rotating. Bathochromic shifts and peak broadening in its electronic spectrum clearly supports the presence of through-space π?π interactions between the two aromatic rings. This should serve as a good model to verify homo-conjugation effect in such a novel system where the two π systems are freely revolving. Copyright
- Jiang, Jianping,Lai, Yee-Hing
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p. 14296 - 14297
(2007/10/03)
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