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RADIATIONLESS DEACTIVATION AND FLUORESCENCE OF SELECTED PYRIDONES
Author(s) -
Guzzo Anthony V.,
Nelson David A.
Publication year - 1992
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1992.tb08508.x
Subject(s) - intramolecular force , excited state , fluorescence , internal conversion , quantum yield , chemistry , relaxation (psychology) , photochemistry , hydrogen bond , solvent , absorption (acoustics) , pyridine , absorption spectroscopy , spectral line , atomic physics , materials science , molecule , stereochemistry , optics , organic chemistry , physics , psychology , social psychology , astronomy , composite material
— Numerous 3‐position derivatives of 2‐hydroxy pyridine, also known as 2‐pyridone, were synthesized and their optical absorption and fluorescence spectra examined. The quantum yield of emission varied from near zero to near unity depending on the kind of substitution made and the solvent. Data are presented that argue for the π‐π* nature of the first excited state in all cases. It was concluded that intramolecular hydrogen bonding controls the extent of internal conversion and hence the amount of fluorescence. It is proposed that this hydrogen bonding suppresses the low energy out of plane vibrations necessary for internal conversion as required by the proximity effect. From studies of the temperature dependence of the emissions, it appeared that the energy separation of the first two excited states, in all cases ˜12.6 ± 2 kJ/mol (3000 ± 500 cal/mol), is not correlated to the extent of relaxation