Intramolecularelectron transfer for which the relevant electronic interaction between the donor and acceptor sites
is mediated by through-bond interaction, i.e. via the covalent bonds interconnecting
these sites, as opposed to through-space interaction.
Source:
PAC, 1996, 68, 2223
(Glossary of terms used in photochemistry (IUPAC Recommendations 1996))
on page 2280