Issue 3, 2021

Mechanisms of photoredox catalysts: the role of optical spectroscopy

Abstract

Photoinduced organic transformations have stimulated the organic chemistry community to develop light-driven renewed reaction methodologies, which in many cases are complementary to standard thermal catalysis. This revitalization of photoinduced transformations is in part due to the straightforward access to powerful photosensitizers. Among them, Ru(II) and Ir(III) polypyridyl complexes have been extensively utilized as prototypical photoredox catalysts. Despite the flourishing of new organic reactivity, studies of photocatalytic cycles are still scarce. The current mechanistic proposal mostly relies on luminescence quenching studies, redox potentials, and bond-dissociation energy values, which provide an essential but partial picture of the catalytic processes. Besides, the quantum efficiency and overall energy efficiency of photoredox organic transformations are not usually considered merit yet. On the other hand, during the last few decades, the photochemistry community has studied the energy and electron transfer mechanism of transition metal complexes from the ground and the excited state extensively, with a partial address of the catalytic photoredox cycles probably due to their complexity. Those studies are needed to develop new photoredox organic transformations further and make them more sustainable and energy-efficient. In this review, we outline an overview of selected basic concepts of photophysics and photochemistry encountered in the photocatalytic cycles. Selected examples are detailed to illustrate how steady-state and time-resolved optical spectroscopy can be employed to elucidate catalytic intermediates and photocatalytic mechanisms. As such, this review aims to motivate mechanistic studies on photoredox catalysis and serves as a guide to perform them to develop more sustainable and energy-efficient chemical transformations.

Graphical abstract: Mechanisms of photoredox catalysts: the role of optical spectroscopy

Article information

Article type
Review Article
Submitted
27 Sept. 2020
Accepted
11 Dec. 2020
First published
20 Janv. 2021

Sustainable Energy Fuels, 2021,5, 638-665

Mechanisms of photoredox catalysts: the role of optical spectroscopy

N. Kandoth, J. Pérez Hernández, E. Palomares and J. Lloret-Fillol, Sustainable Energy Fuels, 2021, 5, 638 DOI: 10.1039/D0SE01454K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements