Issue 30, 2018

How can infra-red excitation both accelerate and slow charge transfer in the same molecule?

Abstract

A UV-IR-Vis 3-pulse study of infra-red induced changes to electron transfer (ET) rates in a donor–bridge–acceptor species finds that charge-separation rates are slowed, while charge-recombination rates are accelerated as a result of IR excitation during the reaction. We explore the underpinning mechanisms for this behavior, studying IR-induced changes to the donor–acceptor coupling, to the validity of the Condon approximation, and to the reaction coordinate distribution. We find that the dominant IR-induced rate effects in the species studied arise from changes to the density of states in the Marcus curve crossing region. That is, IR perturbation changes the probability of accessing the activated complex for the ET reactions. IR excitation diminishes the population of the activated complex for forward (activationless) ET, thus slowing the rate. However, IR excitation increases the population of the activated complex for (highly activated) charge recombination ET, thus accelerating the charge recombination rate.

Graphical abstract: How can infra-red excitation both accelerate and slow charge transfer in the same molecule?

Supplementary files

Article information

Article type
Edge Article
Submitted
08 Jan 2018
Accepted
26 Jun 2018
First published
27 Jun 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2018,9, 6395-6405

How can infra-red excitation both accelerate and slow charge transfer in the same molecule?

Z. Ma, Z. Lin, Candace M. Lawrence, I. V. Rubtsov, P. Antoniou, S. S. Skourtis, P. Zhang and D. N. Beratan, Chem. Sci., 2018, 9, 6395 DOI: 10.1039/C8SC00092A

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