Sequentially Coupled Hole–Electron Transfer Pathways for Bridge-Mediated Triplet Excitation Energy Transfer

Abstract

The donor–acceptor electronic coupling for a bridge-mediated triplet excitation energy transfer (EET) was analyzed to determine the tunneling pathway using intergroup tunneling configuration fluxes. In the singlet EET, the electronic coupling is primarily composed of direct coupling between the donor and acceptor with a secondary contribution from bridge-mediated single-step through-exciton pathways. In contrast, the triplet EET is dominated by superexchange interactions due to the Förster-type interaction becoming forbidden. The triplet EET tunneling pathways are characterized as a sequentially coupled hole and electron transfer (CHET) for both direct and bridge-mediated EETs. This is the first report concerning the difference between the triplet and singlet EETs of the electronic mechanism of bridge-mediated superexchange mechanisms.