Term: outer-sphere electron transfer
https://doi.org/10.1351/goldbook.O04351

Definition:
An outer-sphere electron transfer is a reaction in which the electron transfer takes place with no or very weak (4-16 kJ mol-1) electronic interaction between the reactants in the transition state. If instead the donor and the acceptor exhibit a strong electronic coupling, the reaction is described as inner-sphere electron transfer. The two terms derive from studies concerning metal complexes and it has been suggested that for organic reactions the terms 'nonbonded' and 'bonded' electron transfer should be used.

Related Terms:
1) inner-sphere electron transfer (http://doi.org/10.1351/goldbook.I03052).
2) electron transfer (http://doi.org/10.1351/goldbook.E02011).
3) transition state (http://doi.org/10.1351/goldbook.T06468).
4) coupling (http://doi.org/10.1351/goldbook.C01025).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1148 (https://doi.org/10.1351/pac199466051077)

Citation: 'outer-sphere electron transfer' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.O04351

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