High-Pressure Picosecond Time-Resolved Fluorescence Studies on the Excited Intramolecular Charge-Transfer Kinetics of 4-(9-Anthrylmethyl)-N,N-Dimethylaniline in Alcohol

Picosecond time-resolved fluorescence spectroscopy has been used to examine the dynamic solvent effect on the excited intramolecular charge-transfer (ICT)-state formation in 4-(9-anthrylmethyl)-N,N-dimethylaniline (AMDMA) in linear alcohol solvents as a function of pressure. The non-exponential population decay of the local excited (LE)-state emission is analyzed by fitting to a double exponential function. As solvent viscosity increases, the rate of the ICT-state formation of AMDMA becomes noticeably faster than the solvent relaxation time, which is gauged by the longitudinal relaxation time of the solvent (τ_L). The pressure effect on the ICT reaction of AMDMA in the excited state can be accounted for in terms of the pressure-tuning effect of the solvent viscosity.

In addition, the time-dependent Stokes shift (TDSS) of the ICT emission is measured at high pressures.