(chemistry) a reaction in which a single electron is transferred from one molecule to another; one being oxidized and the other reduced (also known as a redox reaction); long-range electron transfer reactions are important in biological reactions involving metalloproteins such as haemoglobin

Outer sphere refers to an electron transfer event that occurs between chemical species that remain separate and intact before, during, and after the ET event.

Schematic of Dexter electron (energy) transfer|250px|thumb|right

Schematic of photoinduced electron transfer process|thumb|right|400px

A Proton-coupled electron transfer is a chemical reaction that involves the transfer of electrons and protons from one atom to another.