Conformational dynamics modulating electron transfer

TL;DR

This paper introduces a new model for electron transfer that accounts for the conformational dynamics of donor-acceptor distances and their interplay with solvent polarization, revealing a crossover in transfer regimes.

Contribution

It presents a novel solution integrating medium and donor-acceptor dynamics into the electron transfer rate, highlighting the impact of conformational flexibility on transfer efficiency.

Findings

Flexible donor-acceptor complexes favor solvent-controlled electron transfer.

The rate constant exhibits a crossover from distance-independent to exponential decay.

Designing energy chains near the crossover distance optimizes electron transfer.

Abstract

Diffusional dynamics of the donor-acceptor distance in electron-transfer reactions are responsible for the appearance of a new time scale of diffusion over the distance of falloff of electronic tunneling. The distance dynamics compete with the medium polarization dynamics in the solvent-controlled electron transfer kinetics. A new solution incorporating the medium and donor-acceptor dynamics into the electron-transfer rate constant is proposed. The pre-exponential factor of the rate constant switches between a distance-independent solvent-controlled regime and exponential distance decay. The crossover between two regimes is controlled by an effective relaxation time slowed down by a factor exponentially depending on the variance of the donor-acceptor displacement. Flexible donor-acceptor complexes must show a greater tendency for solvent-controlled electron transfer. Electron-transfer energy chains are best designed by placing the redox cofactors near the crossover distance.