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THE PHOTOPHYSICS OF 5‐METHOXYINDOLE. A NON‐EXCIPLEX FORMING INDOLE: ADDITIONAL EVIDENCE FOR TWO CLASSES OF EXCIPLEXES *
Author(s) -
Hershberger Martin V.,
Lumry Rufus W.
Publication year - 1976
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.1751-1097.1976.tb07271.x
Subject(s) - indole test , quantum yield , photochemistry , chemistry , fluorescence , quenching (fluorescence) , excited state , excimer , cyclohexane , dipole , yield (engineering) , solvent , stereochemistry , materials science , atomic physics , organic chemistry , physics , quantum mechanics , metallurgy
— 5‐Methoxyindole is a non‐exciplex forming indole, and its excited state behavior is qualitatively different from that of indole and its methyl substituted derivatives. This fact supports the idea that there are two limiting classes of exciplexes, charge‐transfer and dipole‐dipole stabilized. The fluorescence quantum yield in water is 0.29 with a lifetime of 4.0 ns at 25d̀C. The activation energy for fluorescence quenching in water is 15.9 pM 0.5 kJ/mol, which is smaller than for indole and the methyl substituted indoles which have been measured. In cyclohexane at 25d̀C, the fluorescence quantum yield is 0.63 with a lifetime of 6.7 ns. The fluorescence is efficiently quenched by electron scavengers, as is the case for other indoles. Some electron ejection to solvent probably occurs in both solvents.