Proton-Coupled Electron Transfer: Large-Scale Simulations Beyond the Born-Oppenheimer Approximation

• Applicant: Dr. Denis Artiukhin
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545861628

Proton-coupled electron transfer (PCET) plays an important role in many chemical processes in living matter as well as in technologically relevant systems. It often proceeds as a photo-induced reaction, which could involve energetically coupled transitions of several electrons and protons, in a sequential or concerted manner, within a single compound or between different donors and acceptors. This richness of reaction mechanisms severely complicates the analysis and interpretation of experimentally observed PCET events and calls for guidance and support of computational methods. However, realistic theoretical simulations of PCET reactions are by no means trivial and require accounting for the interaction with large molecular environments and treatment of both kinds of transferring particles quantum mechanically. In case of photo-induced processes, the effect of electronic and vibrational excitations needs to be considered as well. None of to date existing computational methods satisfies all these requirements (if any) at once. The proposed research project aims at filling this gap by developing a new quantum chemical approach, which will combine features of Frozen-Density Embedding for quantum chemical calculations of molecular systems composed of several thousand atoms and the Nuclear-Electronic Orbital technique for the quantum mechanical treatment of selected protons. In a short-term perspective, this new approach will allow for accurate yet feasible quantum chemical calculations of PCET vibronic couplings and splittings, which are the key ingredients in the analysis and interpretation of PCET reaction mechanisms. In a long run, calculations of PCET reaction rate constants and kinetic isotope effects, which are measurable experimentally, will become reality. The proposed methodology will effectively complement existing experimental techniques and contribute to our understanding of a plethora of sophisticated biochemical and artificial phenomena involving PCET.

• DFG Programme: Research Grants