Authors:	Neumann, Svenja Wenger, Oliver S. Kerzig, Christoph
Title:	Controlling spin-correlated radical pairs with donor-acceptor dyads : a new concept to generate reduced metal complexes for more efficient photocatalysis
Online publication date:	22-Jun-2021
Year of first publication:	2021
Language:	english
Abstract:	One-electron reduced metal complexes derived from photoactive ruthenium or iridium complexes are important intermediates for substrate activation steps in photoredox catalysis and for the photocatalytic generation of solar fuels. However, owing to the heavy atom effect, direct photochemical pathways to these key intermediates suffer from intrinsic efficiency problems resulting from rapid geminate recombination of radical pairs within the so-called solvent cage. In this study, we prepared and investigated molecular dyads capable of producing reduced metal complexes via an indirect pathway relying on a sequence of energy and electron transfer processes between a Ru complex and a covalently connected anthracene moiety. Our test reaction to establish the proof-of-concept is the photochemical reduction of ruthenium(tris)bipyridine by the ascorbate dianion as sacrificial donor in aqueous solution. The photochemical key step in the Ru-anthracene dyads is the reduction of a purely organic (anthracene) triplet excited state by the ascorbate dianion, yielding a spin-correlated radical pair whose (unproductive) recombination is strongly spin-forbidden. By carrying out detailed laser flash photolysis investigations, we provide clear evidence for the indirect reduced metal complex generation mechanism and show that this pathway can outperform the conventional direct metal complex photoreduction. The further optimization of our approach involving relatively simple molecular dyads might result in novel photocatalysts that convert substrates with unprecedented quantum yields.
DDC:	540 Chemie 540 Chemistry and allied sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-6016
Version:	Published version
Publication type:	Zeitschriftenaufsatz
License:	CC BY-NC
Information on rights of use:	https://creativecommons.org/licenses/by-nc/4.0/
Journal:	Chemistry - a European journal 27 12
Pages or article number:	4115 4123
Publisher:	Wiley-VCH
Publisher place:	Weinheim
Issue date:	2021
ISSN:	1521-3765
Publisher URL:	https://doi.org/10.1002/chem.202004638
Publisher DOI:	10.1002/chem.202004638
Appears in collections:	JGU-Publikationen