Article
Simulation of Solution Phase Electron Transfer in a Compact Donor–Acceptor Dyad
Journal of Physical Chemistry B
(2011)
Abstract
Charge separation (CS) and charge recombination (CR) rates in photosynthetic architectures are difficult to control, yet their ratio can make or break photon-to-current conversion efficiencies. A rational design approach to the enhancement of CS over CR requires a mechanistic understanding of the underlying electron-transfer (ET) process, including the role of the environment. Toward this goal, we introduce a QM/MM protocol for ET simulations and use it to characterize CR in the formanilide–anthraquinone dyad (FAAQ). Our simulations predict fast recombination of the charge-transfer excited state, in agreement with recent experiments. The computed electronic couplings show an electronic state dependence and are weaker in solution than in the gas phase. We explore the role of cis–trans isomerization on the CR kinetics, and we find strong correlation between the vertical energy gaps of the full simulations and a collective solvent polarization coordinate. Our approach relies on constrained density functional theory to obtain accurate diabatic electronic states on the fly for molecular dynamics simulations, while orientational and electronic polarization of the solvent is captured by a polarizable force field based on a Drude oscillator model. The method offers a unified approach to the characterization of driving forces, reorganization energies, electronic couplings, and nonlinear solvent effects in light-harvesting systems.
Keywords
- Electron transfer
Disciplines
Publication Date
2011
Publisher Statement
Copyright 2011 American Chemical Society
Citation Information
Tim Kowalczyk, Lee-Ping Wang, Troy Van Voorhis (2011) Simulation of solution phase electron transfer in a compact donor-acceptor dyad. J. Phys. Chem. B 115 (42), 12135-12144.