Influence of fluorinated group on the photophysics of 7-aminocoumarins

The photophysical properties of fluorinated 7-aminocoumarin derivatives with different alkylation degree at the amino group are studied in water/ethanol mixtures. The effect of the molecular structure of the chromophore and solute-protic solvent interactions are considered to explain the observed spectral shifts and the internal conversion process. The radiationless deactivation process is analyzed on the basis of the formation of a twisted intramolecular charge transfer state and a planar-to-pyramidal structural change of the amino group.