title: Dexter energy transfer pathways.
abstract: Energy transfer with an associated spin change of the donor and acceptor, Dexter energy transfer, is critically important in solar energy harvesting assemblies, damage protection schemes of photobiology, and organometallic opto-electronic materials. Dexter transfer between chemically linked donors and acceptors is bridge mediated, presenting an enticing analogy with bridge-mediated electron and hole transfer. However, Dexter coupling pathways must convey both an electron and a hole from donor to acceptor, and this adds considerable richness to the mediation process. We dissect the bridge-mediated Dexter coupling mechanisms and formulate a theory for triplet energy transfer coupling pathways. Virtual donor-acceptor charge-transfer exciton intermediates dominate at shorter distances or higher tunneling energy gaps, whereas virtual intermediates with an electron and a hole both on the bridge (virtual bridge excitons) dominate for longer distances or lower energy gaps. The effects of virtual bridge excitons were neglected in earlier treatments. The two-particle pathway framework developed here shows how Dexter energy-transfer rates depend on donor, bridge, and acceptor energetics, as well as on orbital symmetry and quantum interference among pathways.
authors.affiliation: Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus; david.beratan@duke.edu skourtis@ucy.ac.cy.
authors.forename: Spiros S
authors.initials: SS
authors.lastname: Skourtis
authors.affiliation: Department of Chemistry, Duke University, Durham, NC 27708;
authors.forename: Chaoren
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus;
authors.forename: Panayiotis
authors.initials: P
authors.lastname: Antoniou
authors.affiliation: Department of Chemistry, Duke University, Durham, NC 27708; Bio/Nano Research Group, Autodesk Inc., San Francisco, CA 94111;
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Virshup
authors.affiliation: Department of Chemistry, Duke University, Durham, NC 27708; Department of Physics, Duke University, Durham, NC 27708; Department of Biochemistry, Duke University, Durham, NC 27710 david.beratan@duke.edu skourtis@ucy.ac.cy.
authors.forename: David N
authors.initials: DN
authors.lastname: Beratan
keywords: Dexter energy transfer; superexchange; triplet energy transfer; triplet excitons; two-particle coupling pathways