Proton-Coupled Electron Transfer
- Proton-coupled electron transfer (PCET) reactions play a critical role in a variety of chemical and biological processes, including photosynthesis, various enzyme reactions, and energy devices such as solar cells.
- We have developed a general theoretical formulation for PCET and have applied this theory to a wide range of experimentally studied reactions in solution, proteins, and electrochemistry.
- We have written several reviews on PCET. 43, 106, 132, 152, 194
We have developed a general theoretical formulation for PCET reactions. This theory includes the quantum mechanical effects of the active electrons and transferring protons, as well as the motions of the proton donor-acceptor mode and solvent or protein environment. We have derived analytical nonadiabatic rate constant expressions in various well-defined regimes. The original formulation was based on a multistate continuum theory with fixed proton donor-acceptor distance.30, 35 Subsequent extensions included the dynamical effects of an explicit molecular solvent or protein environment, as well as the proton donor-acceptor vibrational motion.69, 74, 77, 200, 216 We have also extended this theory to electrochemical systems.102, 104, 115
In addition, we have developed diabatization schemes for generating charge-localized diabatic electron-proton vibronic states136, 144 and methods for calculating the vibronic coupling between these states.90, 136, 152, 197 We have also identified hydrogen atom transfer (HAT) and electron-proton transfer (EPT) with electronically adiabatic and nonadiabatic proton transfer, respectively,90, 136, 152, 197 and have devised quantitative diagnostics for determining whether systems are in the electronically adiabatic or nonadiabatic regime.90, 136, 152, 197
We have also developed the methodology for mixed quantum/classical molecular dynamics simulations with explicit solvent for PCET reactions.15, 18, 19, 27, 47, 74, 77 In addition, we have developed nonadiabatic dynamics methods for simulating the ultrafast nonequilibrium dynamics of photoinduced PCET reactions for model systems.119, 122, 130, 135, 147 Recently we extended these methods to enable the study of experimentally relevant molecular systems embedded in explicit solvent with mixed quantum mechanical/molecular mechanical (QM/MM) potential energy surfaces computed on-the-fly using multiconfigurational QM methods.189, 195, 205, 218
More recently, we have developed theoretical formulations for electrochemical PCET and have studied proton discharge on electrode surfaces.248, 254, 260, 290 The most general theory290 spans the adiabatic and nonadiabatic regimes and includes the effects of vibrational nonadiabaticity and solvent dynamics. Moreover, we have developed theoretical methods to compute the frequencies of vibrational probes at electrode interfaces to enable the investigation of electric fields at electrochemical interfaces.272, 305