FORMATION AND DECAY OF THE ETHYL P-(N,N-DIETHYLAMINO)BENZOATE TWISTEDINTRAMOLECULAR CHARGE-TRANSFER STATE IN THE VAPOR-PHASE, SUPERCRITICAL FLUIDS, AND ROOM-TEMPERATURE SOLUTIONS

The fluorescence properties of ethyl p-(N,N-diethylamino)benzoate (DEA EB) are studied in the vapor phase, supercritical fluids, and room-tem perature solutions. Dual emission in the vapor phase due to the format ion of a twisted intramolecular charge-transfer (TICT) state is observ ed. Relative emission contributions of the locally excited (LE) and TI CT states are determined for DEAEB under different conditions by apply ing chemometric spectral resolution methods to observed dual fluoresce nce spectral mixtures. The TICT emission contribution accounts for 27 +/- 5% of the total fluorescence in the vapor phase and 80-97% in room -temperature solutions. Decays of the TICT state are strongly solvent dependent and follow the energy gap relationship from radiationless de cay theories. For DEAEB in alcohol and aqueous solutions, the small fl uorescence quantum yields are attributed to fluorescence quenching tha t is associated with specific solute-solvent interactions such as hydr ogen bonding.