1,5-Prodan Emits from a Planar Intramolecular Charge-Transfer Excited State.

1-Propionyl-5-dimethylaminonaphthalene (, 1,5-Prodan) and two derivatives where the amino group is constrained in a seven-membered () and five-membered () ring are prepared. All three exhibit strong fluorescence and similar degrees of solvatochromism. Their fluorescence is strongly quenched in alcohol solvents.