Electron Transfer Dynamics in Chemical and Biological Systems

Electron transfer underpins a vast array of processes in chemistry and biology, from photosynthetic light harvesting and cellular respiration to synthetic charge-transport materials. At its core, the rate and efficiency of transfer between donor and acceptor sites are governed by the electronic coupling between redox centres, the reorganisation energy of the surrounding medium and the thermal activation barrier described by Marcus theory. In chemical systems, electron tunnelling across molecular bridges and through solid-state interfaces determines the performance of organic semiconductors, catalysts and energy storage devices. In biological contexts, finely tuned protein matrices and solvent environments modulate coupling strengths and polarisation, achieving directional flow with minimal energy loss. The interplay of adiabatic and nonadiabatic regimes, where nuclear motion either follows or decouples from electronic transitions, shapes reaction pathways over femtosecond to millisecond timescales. Advances in ultrafast spectroscopy, two-dimensional optical techniques and computational modelling have elucidated key transfer coordinates and revealed how vibrational modes, solvent dynamics and protein fluctuations assist or impede charge migration. This mechanistic insight informs the design of more efficient catalysts, robust solar energy converters and biomimetic systems, emphasising the global importance of controlling electron transfer dynamics at the atomic and molecular level.

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Electron Transfer Dynamics in Chemical and Biological Systems publication trend

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Technical terms

Electronic coupling: A measure of the quantum mechanical interaction between donor and acceptor orbitals that governs the probability of electron transfer.

Adiabatic regime: A transfer regime in which electronic transitions occur on a timescale slow enough that nuclear motion adapts instantaneously to changes in electronic state.

Nonadiabatic regime: A transfer regime where electronic transitions occur faster than nuclear rearrangement, requiring explicit treatment of vibronic coupling.

Marcus theory: A theoretical framework that relates electron-transfer rates to reorganisation energy, electronic coupling and thermal activation.

Constrained density functional theory (cDFT): A computational method that imposes constraints on electron density or spin populations to model excited or charge-transfer states within a DFT formalism.

References

1. Ultrafast Electronic Coupling Estimators: Neural Networks versus Physics-Based Approaches. Journal of Chemical Theory and Computation (2023).
2. Constrained Density Functional Theory: A Potential-Based Self-Consistency Approach. Journal of Chemical Theory and Computation (2022).
3. HAB79: A new molecular dataset for benchmarking DFT and DFTB electronic couplings against high-level ab initio calculations. The Journal of Chemical Physics (2021).