Mechanisms of the delayed luminescence of N-methylindole and indole in the gas phase

Spectral and kinetic characteristics of delayed luminescence of N-methylindole and indole in the gas phase have been studied. N-methylindole delayed luminescence represents P-type delayed fluorescence. Its spectrum approximately coincides with a fluorescence spectrum. Indole P-type delayed fluorescence has not been recorded, however, its delayed luminescence in the spectral region with a maximum at λmax = 535 nm has been observed and interpreted as luminescence of free radicals to be formed due to the N-H bond dissociation. It is supposed that the excited states of free radicals are populated due to nonradiative energy transfer from the triplet states of indole to the doublet states of free radicals. Calculated from the kinetics of the delayed luminescence lifetimes of the triplet states of N-methylindole and indole at Т = 373 K are 2.5 and 1 ms, respectively.