Analysis of the solvent effect on the photophysics properties of 6-propionyl-2-(dimethylamino)naphthalene (PRODAN).

The absorption and emission spectroscopic properties of 6-propionyl-2-(dimethylamino)naphthalene (PRODAN) have been studied in a large number of protogenic, nonprotogenic, and amphiprotic solvents. The data obtained can be explained by the inclussion of a new term in the Lippert equation which takes into account the acidity of the solvent. This finding indicates that some precaution should be taken when using PRODAN as an indicator of the polarity of protein cavities if the environments involved include acid sites.