ANILLNOPYRIDINIUM - SOLVENT-DEPENDENT FLUORESCENCE BY INTRAMOLECULAR CHARGE-TRANSFER

Considerable intramolecular charge transfer is induced in anilinopyridinium by electronic excitation and by twist of the central single bond. Polar solvents shift the absorption spectrum to the blue and the fluorescence spectrum to the red. The effect may be assigned to an enhanced reorganization energy as described by Marcus' formula for intermolecular electron transfer. The quantum yield of fluorescence is lowered by polar media. The effect may be assigned to a lowered energy barrier leading to a nonfluorescent twisted internal charge-transfer (TICT) state as described by a Kramers-Born formula that accounts for solvation and friction.