Volume 247, 2023

Spatio-temporal detachment of homogeneous electron transfer in controlling selectivity in mediated organic electrosynthesis

Abstract

In electrosynthesis, electron transfer (ET) mediators are normally chosen such that they are more easily reduced (or oxidised) than the substrate for cathodic (or anodic) processes; setting the electrode potential to the mediator therefore ensures selective heterogeneous ET with the mediator at the electrode, rather than the substrate. The current work investigates the opposite, and counter intuitive, situation for a successful mediated electroreductive process where the mediator (phenanthrene) has a reduction potential that is negative to that of the substrate, and the cathode potential is set negative to both (Eele < EM < Es). Simulations reveal a complex interplay between mass transport, the relative concentrations of the mediator and substrate as well as the heterogeneous and homogeneous rate constants for multiple steps, which under suitable conditions, leads to separation of the homogeneous chemistry in a reaction layer detached from the electrode. Reaction layer detachment is a spatio-temporal effect arising due to opposing fluxes of the mediator radical anion and the substrate 1, which ultimately prevents 1 from reaching the electrode, thereby affording a different reaction pathway. Simulations representative of unstirred batch (1D) and flow (2D) electrolysis are presented, which qualitatively reproduce the experimental selectivity outcomes for mediated and unmediated electroreductive cyclisation of aryl iodide 1. The potential to use highly reducing homogeneous ET agents, possessing reduction potentials beyond those of the substrates, offers exciting opportunities in mediated electrosynthesis.

Graphical abstract: Spatio-temporal detachment of homogeneous electron transfer in controlling selectivity in mediated organic electrosynthesis

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
03 พ.ค. 2566
Accepted
31 พ.ค. 2566
First published
06 มิ.ย. 2566
This article is Open Access
Creative Commons BY license

Faraday Discuss., 2023,247, 302-323

Spatio-temporal detachment of homogeneous electron transfer in controlling selectivity in mediated organic electrosynthesis

Jack W. Hodgson, A. A. Folgueiras-Amador, D. Pletcher, D. C. Harrowven, G. Denuault and R. C. D. Brown, Faraday Discuss., 2023, 247, 302 DOI: 10.1039/D3FD00089C

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.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements