Modeling Excited-State Proton Transfer to Solvent: A Dynamics Study of a Super Photoacid with a Hybrid Implicit/Explicit Solvent Model
Umberto Raucci, Maria Gabriella Chiariello, Nadia Rega
Abstract
90). The sampling of the solvent configuration space on the ground electronic state is the first key step toward the simulation of the ESPT event. Therefore, several configurations in the Franck-Condon region, describing an average solvation, were chosen as starting points for the excited-state dynamics. In all cases, the excited-state evolution spontaneously leads to the proton transfer event, whose rate is strongly dependent on the hydrogen bond network around the proton acceptor solvent molecule. Our study revealed that the explicit representation at least of three solvation shells around the proton acceptor molecule is necessary to stabilize the excess proton. Furthermore, the analysis of the solvent molecule motions in proximity of the reaction site suggested that even in the case of the strongest photoacid, the ESPT is actually assisted by the solvation dynamics of the first and second solvation shells of the water accepting molecule.