Excited-state charge transfer dynamics of p-dimethylaminobenzonitrile in quadrupolar solvents

Excited-state intramolecular charge transfer of p-dimethylaminobenzonitrile (DMABN) in benzene, toluene, and dioxane is studied. By combining the recent continuum quadrupolar solvent theory of Jeon and Kim [J. Phys. Chem. A 2000, 104, 9812] and the two-dimensional formulation of the DNABN photoreaction in dipolar solvents by Fonseca et al. [J. Mol. Liq. 1994, 60, 161], the influence of both solvent quadrupole reorganization and solute twist on the reaction free energetics and dynamics is accounted for. The solution-phase reaction paths are investigated with the aid of experimental information on the frequencies associated with solute torsional and collective solvent quadrupole dynamics. The rate constants and transmission coefficients are analyzed using transition state theory with the neglect of dissipative dynamics. Our results are in reasonable agreement with the experimental findings in quadrupolar solvents.