An intermolecular hydrogen-bonding effect on spectral and photophysical properties of 6-aminocoumarin in protic solvents.

The paper presents results of the spectral (absorption and emission) and photophysical study of 6-aminocoumarin (6AC) in strong protic solvents with different hydrogen-bond acidity. The measurements of the fluorescence lifetime and quantum yield clearly show that in protic solvents intermolecular hydrogen-bonding interactions between solute and solvent molecules facilitate the nonradiative processes. It is suggested that in these solvents very efficient internal conversion due to intermolecular hydrogen-bonding is induced. A large isotope effect is found for 6AC in deuterated water.