Issue 42, 2024

The role of an intramolecular hydrogen bond in the redox properties of carboxylic acid naphthoquinones

Abstract

A bioinspired naphthoquinone model of the quinones in photosynthetic reaction centers but bearing an intramolecular hydrogen-bonded carboxylic acid has been synthesized and characterized electrochemically, spectroscopically, and computationally to provide mechanistic insight into the role of proton-coupled electron transfer (PCET) of quinone reduction in photosynthesis. The reduction potential of this construct is 370 mV more positive than the unsubstituted naphthoquinone. In addition to the reversible cyclic voltammetry, infrared spectroelectrochemistry confirms that the naphthoquinone/naphthoquinone radical anion couple is fully reversible. Calculated redox potentials agree with the experimental trends arising from the intramolecular hydrogen bond. Molecular electrostatic potentials illustrate the reversible proton transfer driving forces, and analysis of the computed vibrational spectra supports the possibility of a combination of electron transfer and PCET processes. The significance of PCET, reversibility, and redox potential management relevant to the design of artificial photosynthetic assemblies involving PCET processes is discussed.

Graphical abstract: The role of an intramolecular hydrogen bond in the redox properties of carboxylic acid naphthoquinones

Supplementary files

Article information

Article type
Edge Article
Submitted
06 Aug 2024
Accepted
19 Sep 2024
First published
20 Sep 2024
This article is Open Access

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

Chem. Sci., 2024,15, 17425-17434

The role of an intramolecular hydrogen bond in the redox properties of carboxylic acid naphthoquinones

W. D. Guerra, E. Odella, K. Cui, M. Secor, R. E. Dominguez, E. J. Gonzalez, T. A. Moore, S. Hammes-Schiffer and A. L. Moore, Chem. Sci., 2024, 15, 17425 DOI: 10.1039/D4SC05277C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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