Donor-Bridge-Acceptor Proton Transfer in Aqueous Solution.
We use ab initio molecular dynamics to study proton transfer in a donor-bridge-acceptor system in which the bridge is a single water molecule and the entire system is embedded in aqueous solution. The results, based on a large number of proton transfer trajectories, demonstrate that the dominant charge-transfer pathway is a subpicosecond "through bridge" event in which the bridge adopts an Eigen-like (hydronium) structure. We also identify another state in which the bridge forms a Zundel-like configuration with the acceptor that appears to be a dead end for the charge transfer. The reaction coordinate is inherently multidimensional and, as we demonstrate, cannot be given in terms of either local structural parameters of the donor-bridge-acceptor system or local solvent coordination numbers.
†Département de Chimie, Université de Montréal, CP 6128, succursale Centre-Ville, Montréal H3C3J7, Canada.
Ugo
U
Rivard
†Département de Chimie, Université de Montréal, CP 6128, succursale Centre-Ville, Montréal H3C3J7, Canada.
Vibin
V
Thomas
‡Departments of Chemistry and Physics, Center for the Physics of Materials, McGill University, 801 Sherbrooke Street West, Montréal H3A2K6, Canada.
Andrew
A
Bruhacs
‡Departments of Chemistry and Physics, Center for the Physics of Materials, McGill University, 801 Sherbrooke Street West, Montréal H3A2K6, Canada.
Bradley
B
Siwick
†Département de Chimie, Université de Montréal, CP 6128, succursale Centre-Ville, Montréal H3C3J7, Canada.
Radu
R
Iftimie
Eigen intermediate; Zundel form; ab initio molecular dynamics; acid−base reaction; charge transfer; concerted mechanism