MullikenHush

Mulliken-Hush theory is a theoretical framework for describing the rates of electron transfer (ET) reactions. Proposed by Robert Mulliken and John Hush, it builds on frontier orbital theory, focusing on the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of donor and acceptor species. The theory posits that the ET rate constant (k_ET) is exponentially dependent on the energy gap (ΔE) between these frontier orbitals, with the relationship k_ET ∝ exp(-βΔE), where β is a constant related to reorganization energy and electronic coupling. Additionally, the symmetry of the frontier orbitals must be compatible for efficient ET. This model has been widely applied to understand processes such as photosynthetic charge separation, redox reactions in electrochemistry, and molecular electronics, providing a quantitative basis for predicting and optimizing ET kinetics in various systems.