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 (tau(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.