Ab initio study of the electronic excited states in 4-(N,N-dimethylamino)benzonitrile with inclusion of solvent effects: the internal charge transfer process

The lower singlet excited states for (dimethylamino)benzonitrile (DMABN) have been studied as a function of the twisting and wagging motion with inclusion of solvent effects. Theoretical calculations have been performed using a multireference perturbed CI method, and the solvent effects have been described within the polarizable continuum model (PCM). In the methodology we have used, solvent interactions are explicitly included in the CI scheme and in the following perturbative corrections, through proper operators corresponding to electrostatic and repulsion interactions. The results obtained including solvent interactions both on geometries and energies support the twisted intramolecular charge transfer (TICT) model proposed to explain the dual fluorescence phenomenon occurring in DMABN when immersed in polar solvents. Calculated transition energies (absorption and emission) obtained for both the isolated and the solvated system are in agreement with available experimental information.