Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
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Photophysical Properties of 1,3-Dimethylnaphtho[1,2-e]uracil

  • Shim, Sang-Chul (Department of Chemistry, Korea Advanced Institute of Science and Technology) ;
  • Shin, Eun-Ju (Department of Chemistry, Korea Advanced Institute of Science and Technology) ;
  • Park, Seung-Ki (Department of Chemistry, Korea Advanced Institute of Science and Technology) ;
  • Kang, Ho-Kwon (Department of Chemistry, Korea Advanced Institute of Science and Technology)
  • Published : 1986.06.20
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Abstract

The solvent change and salt do not affect the fluorescence quantum yield of 1,3-dimethylnaphtho[1,2-e]uracil indicating the considerable energy gap between the lowest singlet $({\pi},\;{\pi}^{\ast})\;and\;(n,\;{\pi}^{\ast})$ states in the compound. The results are consistent with the strong quenching of fluorescence by ethyl iodide. Fluorescence quantum yield is nearly independent of temperature, probably due to the relatively inefficient internal conversion. Unusual spectral difference is observed in isopentane and ethanol at 77K. The temperature dependence of emission in isopentane and in ethanol suggests that the increase of charge transfer character by the conformational change in isopentane leads to the structureless and red-shifted fluorescence, while in ethanol the decrease of the charge transfer character by the hydrogen bonding interaction results in the structured and blue-shifted fluorescence along with phosphorescence at the low temperature. Temperature dependence of emission in poly(methylmethacrylate) matrix indicates that $T_1{\to}S_0$ radiationless decay is an important process responsible for the strong temperature dependence of phosphorescence.

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