Dexter electron transfer

Dexter electron transfer (also called Dexter electron exchange and Dexter energy transfer) is a fluorescence quenching mechanism in which an excited electron is transferred from one molecule (a donor) to a second molecule (an acceptor) via a non radiative path.[1][2] This process requires a wavefunction overlap between the donor and acceptor,[3] which means it can only occur at short distances; typically within 10 Å.[4] The excited state may be exchanged in a single step, or in two separate charge exchange steps.

History

This short range energy transfer process was first theoretically proposed by D. L. Dexter in 1953.[5]

Rate expression

The Dexter energy transfer rate, ${\displaystyle k_{ET}}$, is indicated by the proportionality

${\displaystyle k_{ET}\varpropto J\mathrm {exp} \left[{\frac {-2r}{L}}\right]}$

where ${\displaystyle r}$ is the separation of the donor from the acceptor, ${\displaystyle L}$ is the sum of the Van der Waals radii of the donor and the acceptor, and ${\displaystyle J}$ is the spectral overlap integral defined by

${\displaystyle J=\int f_{\rm {D}}(\lambda )\,\epsilon _{\rm {A}}(\lambda )\,\lambda ^{4}\,d\lambda }$