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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 23, Number 9
BKCSDE 23(9)
September 20, 2002 

Substituent Effect on Fluorescence and Photoisomerization of 1-(9-Anthryl)-2-(4-pyridyl)ethenes
Eun Ju Shin, Sang Ha Lee
Diarylethene, Substituent effect, Fluorescence, Photoisomerization
The fluorescence and photoisomerization quantum yields of trans-1-(9-anthryl)-2-(4-pyridyl)ethene (t-4-APyE), 1-(10-methyl-9-anthryl)-2-(4-pyridyl)ethene (t-4-MeAPyE), and 1-(10-chloro-9-anthryl)-2-(4- pyridyl)ethene (t-4-ClAPyE) were measured in cyclohexane, acetonitrile, and methanol at room temperature.Polar solvents result in the drastic reduction of fluorescence quantum yield and increase of photoisomerization quantum yield for all three compounds. These results are probably due to the stabilization of intramolecular charge transfer (ICT) excited state in polar solvent. The higher contribution of ICT in the presence of more electron-donating methyl substituent, manifested by largest positive fluorescence solvatochromism, indicates that the pyridine ring acts as an electron acceptor. Protonation or methylation makes pyridine ring stronger electron acceptor and causes long-wavelength ground state charge transfer absorption band and complete quenching of fluorescence. The fluorescence from t-4-APyE derivatives can be switched off responding external stimuli viz. medium polarity, protonation, or methylation.
1309 - 1314
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