Intramolecular electron transfer and solvation

Abstract

The intramolecular charge transfer reaction and solvation dynamics of 4,4′-dimethylaminophenyl sulphone in alcohols are measured using picosecond time-resolved emission spectroscopy. The results are compared to theoretical models that treat the solvent as a dielectric continuum. In alcohol solvents, the value for τL-1(τL = τDE∞/Es) using either n2 or E mv for E∞ do not provide a good gauge for the intramolecular electron transfer rate. These results are discussed in terms of the importance of vibrational contributions to the reaction rates and the applicability of the parameter τL in gauging the solvent dynamics. In addition, the time-resolved emission data clearly show that the charge transfer state is formed out of equilibrium with the surrounding solvent structure. The measured time scales for the ensuing solvent relaxation are significantly longer than the hydrodynamic continuum model prediction of τL. The discrepancy between the observed rates and those predicted by models based on a dielectric continuum description of the solvent reveal the importance of the underlying molecular aspects of the role of the solvent in both intramolecular charge transfer and solvation. © 1987 American Institute of Physics.