electrontransfer

Electron transfer is the process by which an electron moves from a donor to an acceptor. It can occur within a single molecule (intramolecular) or between molecules or materials (intermolecular). The reaction changes oxidation states and underpins redox chemistry, electrochemistry, and many biological processes. The likelihood and rate of transfer depend on thermodynamic driving force, expressed by redox potentials, and on the reorganization of the surrounding medium, described by Marcus theory.

Transfers proceed through different mechanisms. In inner-sphere electron transfer, a ligand temporarily bridges donor and acceptor to provide a pathway for the electron. In outer-sphere transfer, no direct bond forms between the sites; the electron moves by tunneling or hopping through solvent or through-space. In biology, electron transfer chains route electrons through a series of cofactors to accomplish energy conversion in photosynthesis and respiration. In electrochemistry, electrode reactions involve electron transfer between an electrode and a redox-active species, with current determined by kinetics and overpotential; the Nernst equation gives the equilibrium potential, and rate constants govern the kinetics.

In solid-state and materials chemistry, electron transfer among metal centers or dopants controls conductivity, redox switching, and catalytic activity. Factors such as donor–acceptor distance, electronic coupling, solvent dynamics, and temperature influence rates, often described by an exponential distance dependence for tunneling. Applications include batteries, fuel cells, sensors, catalysts, and organic electronics. Understanding electron transfer requires integrating thermodynamics, kinetics, and environmental effects.