Radiationless deactivation of excited molecules of 4-aminonaphthalimides

The effects of alkylation of the 4-amino group, polarity and viscosity of a solvent, and temperature on the fluorescence of N-(2,4-dimethylphenyl)imides of 4-amino-1,8-naphthalenedicarboxylic acid were studied. A decrease in the temperature and polarity of a solvent and an increase in its viscosity cause the rate of radiationless deactivation of 4-dimethylaminonaphthalimide to decrease and have almost no effect on the rate of emissive deactivation of excited state. The abnormally low efficiency of fluorescence of 4-dimethylaminonaphthalimide in polar low-viscosity media at room temperature is associated with the formation of a nonfluorescent charge-transfer state. The increase in the sate of radiationless deactivation of 4-aminonaphthalimide in the alkylation of its amino group is associated with the increase in its electron-donor ability.