Relaxation dynamics of aniline in methanol: the photoionization channel

The relaxation of aniline after excitation at 267 and 200 nm (4.6 and 6.2 eV) in methanol solutions has been explored by fs time-resolved experiments and the observations interpreted using ab initio calculations on the excited states of aniline-methanol clusters. In contrast to what has been reported under aqueous solvation, excitation at 267 nm does not induce ionization of the molecule and only a photophysical relaxation route is operative. The computational results allow us to rationalize this observation in terms of the different nature that the Rydberg transition, responsible for the electron ejection, presents in analogous N-H⋯O structures seen in methanol and water clusters. On the other hand, ionization of aniline via the direct ejection of an electron into the solvent is identified in methanol following 200 nm excitation, a mechanism analogous to that found in water at this energy.