Correlated reaction coordinate motion produces non-additive rate enhancement for electron and energy transfer in multi-acceptor structures

TL;DR

This paper explains how interactions among multiple acceptors in molecular structures lead to non-additive, significantly enhanced electron and energy transfer rates through correlated reaction coordinate motion, beyond simple additive effects.

Contribution

It reveals the mechanisms by which acceptor-acceptor interactions produce rate enhancements, providing new insights for designing molecular systems with tailored transfer kinetics.

Findings

Rate enhancements beyond twofold arise from acceptor-acceptor interactions.

Interactions shift free energy, modify couplings, and alter reaction-coordinate motion.

Strategies for tuning transfer rates based on these effects are proposed.

Abstract

Molecular structures with multiple donor, bridge, or acceptor units can display quantum interference effects that influence electron and energy transfer (ET and EnT) rates. Recent experiments found a 4- to 5-fold increase in ET rates for donor-acceptor structures with two acceptors compared to one. This result is surprising: simple classical or quantum analysis suggests a factor of two rate enhancement. We analyze the coupling interactions in multiple acceptor systems and find that rate enhancements beyond additive effects arise from acceptor-acceptor interactions that: 1) shift the reaction free energy, 2) change the donor-acceptor couplings, and 3) alter the reaction-coordinate motion. Consideration of these effects explains the observed rates in multi-acceptor systems and suggests strategies to tailor energy and electron transfer kinetics.