Large edge-excitation red-shift of the fluorescence of an ethanol solution of 4-amino-4'-nitrodiphenyl (and). The case of a solute with a dipole moment increase in the excited state

Abstract The observed large edge-excitation red-shift of the fluorescence of 4-amino-4'-nitrodiphenyl (AND) in a rigid ethanol medium and the red-shift of the absorption band as the temperature is lowered are explained in terms of a microscopic solvent heterogeneity. The AND results where the dipole moment is increased upon excitation are compared with the merocyanine dye results where the reverse is true.