Proton-coupled electron transfer enhances the electrocatalytic reduction of nitrite to no in a bioinspired copper complex

Cioncoloni, G., Roger Barba, I., Wheatley, P. S., Wilson, C. , Morris, R. E., Sproules, S. and Symes, M. D. (2018) Proton-coupled electron transfer enhances the electrocatalytic reduction of nitrite to no in a bioinspired copper complex. ACS Catalysis, 8(6), pp. 5070-5084. (doi: 10.1021/acscatal.8b00361)

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The selective and efficient electrocatalytic reduction of nitrite to nitric oxide (NO) is of tremendous importance, both for the development of NO-release systems for biomedical applications and for the removal of nitrogen oxide pollutants from the environment. In nature, this transformation is mediated by (among others) enzymes known as the copper-containing nitrite reductases. The development of synthetic copper complexes that can reduce nitrite to NO has therefore attracted considerable interest. However, there are no studies describing the crucial role of proton-coupled electron transfer during nitrite reduction when such synthetic complexes are used. Herein, we describe the synthesis and characterization of two previously unreported Cu complexes (3 and 4) for the electrocatalytic reduction of nitrite to NO, in which the role of proton-relaying units in the secondary coordination sphere of the metal can be probed. Complex 4 bears a pendant carboxylate group in close proximity to the copper center, while complex 3 lacks such functionality. Our results suggest that complex 4 is twice as effective an electrocatalyst for nitrite reduction than is complex 3 and that complex 4 is the best copper-based molecular electrocatalyst for this reaction yet discovered. The differences in reactivity between 3 and 4 are probed using a range of electrochemical, spectroscopic, and computational methods, which shed light on the possible catalytic mechanism of 4 and implicate the proton-relaying ability of its pendant carboxylate group in the enhanced reactivity that this complex displays. These results highlight the critical role of proton-coupled electron transfer in the reduction of nitrite to NO and have important implications for the design of biomimetic catalysts for the selective interconversions of the nitrogen oxides.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Sproules, Dr Stephen and Roger Barba, Isolda and Cioncoloni, Giacomo and Wilson, Dr Claire and Symes, Professor Mark
Authors: Cioncoloni, G., Roger Barba, I., Wheatley, P. S., Wilson, C., Morris, R. E., Sproules, S., and Symes, M. D.
College/School:College of Science and Engineering
College of Science and Engineering > School of Chemistry
Journal Name:ACS Catalysis
Publisher:American Chemical Society
ISSN (Online):2155-5435
Published Online:25 April 2018
Copyright Holders:Copyright © 2018 American Chemical Society
First Published:First published in ACS Catalysis 8(6): 5070-5084
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
621311Upgrading the small scale equipment base for early career researchers in the engineering and physical sciencesMiles PadgettEngineering and Physical Sciences Research Council (EPSRC)EP/K031732/1S&E P&A - PHYSICS & ASTRONOMY