Electron transfer

Electron transfer is a process where an electron moves from one atom, ion, or molecule to another. This helps explain how electrons move in reactions called redox reactions.

Many important natural and industrial processes depend on electron transfer. For example, it is part of electrochemical processes, like in batteries. Electron transfer is also important in photosynthesis and respiration, which are how plants make food and how living things get energy.

In organic chemistry, electron transfer is part of some reactions used to make new materials. It is also key in photoredox catalysis, a modern way to speed up chemical reactions using light. Learning about electron transfer helps scientists and engineers improve technologies and understand nature better.

Classes of electron transfer

Inner-sphere electron transfer

Main article: Inner-sphere electron transfer

In inner-sphere electron transfer, two parts that can change their charge are connected by a bridge when the transfer happens. This bridge can be part of the same molecule. Sometimes, the bridge only forms right before the transfer.

Outer-sphere electron transfer

Main article: Outer-sphere electron transfer

In outer-sphere electron transfer, the parts that change their charge are not connected by a bridge. The electron moves through space from one to the other. This can happen between different chemicals. A good example is a reaction between permanganate and its reduced form.

Outer-sphere electron transfer usually happens when the chemicals don’t change shape easily.

Five steps of an outer sphere reaction

1. The chemicals come close together.
2. The bonds and surrounding material change shape.
3. The electron moves.
4. The bonds and surrounding material settle back.
5. The products move apart.

Heterogeneous electron transfer

In heterogeneous electron transfer, an electron moves between a chemical in liquid and the surface of a solid like a semi-conducting material or an electrode. This is important for electrochemistry and making solar cells.

Vectorial electron transfer

In proteins, electrons often move from one spot to another in a line. This path helps the electron travel through materials that normally don’t conduct electricity well. Common spots for these electrons are iron-sulfur clusters.

Theory

The first idea about how electrons move between atoms was created by Rudolph A. Marcus. He won a Nobel Prize in Chemistry in 1992. His work focused on a special type of electron movement called outer-sphere electron transfer.

Later, Noel Hush and Marcus expanded this idea to include inner-sphere electron transfer. This created what is now known as Marcus-Hush theory. These theories help scientists understand how electrons move in chemical reactions.

Other scientists like Joshua Jortner have studied this process in more detail. In proteins, how electrons move depends on the shape of the protein bonds.