1
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Wang C, Li H, Bürgin TH, Wenger OS. Cage escape governs photoredox reaction rates and quantum yields. Nat Chem 2024; 16:1151-1159. [PMID: 38499849 PMCID: PMC11230909 DOI: 10.1038/s41557-024-01482-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 02/20/2024] [Indexed: 03/20/2024]
Abstract
Photoredox catalysis relies on light-induced electron transfer leading to a radical pair comprising an oxidized donor and a reduced acceptor in a solvent cage. For productive onward reaction to occur, the oxidized donor and the reduced acceptor must escape from that solvent cage before they undergo spontaneous reverse electron transfer. Here we show the decisive role that cage escape plays in three benchmark photocatalytic reactions, namely, an aerobic hydroxylation, a reductive debromination and an aza-Henry reaction. Using ruthenium(II)- and chromium(III)-based photocatalysts, which provide inherently different cage escape quantum yields, we determined quantitative correlations between the rates of photoredox product formation and the cage escape quantum yields. These findings can be largely rationalized within the framework of Marcus theory for electron transfer.
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Affiliation(s)
- Cui Wang
- Department of Chemistry, University of Basel, Basel, Switzerland
- Department of Biology and Chemistry, Osnabrück University, Osnabrück, Germany
| | - Han Li
- Department of Chemistry, University of Basel, Basel, Switzerland
| | - Tobias H Bürgin
- Department of Chemistry, University of Basel, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, Basel, Switzerland.
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2
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Bürgin T, Ogawa T, Wenger OS. Better Covalent Connection in a Molecular Triad Enables More Efficient Photochemical Energy Storage. Inorg Chem 2023; 62:13597-13607. [PMID: 37562775 PMCID: PMC10445269 DOI: 10.1021/acs.inorgchem.3c02008] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Indexed: 08/12/2023]
Abstract
Numerous studies have explored the kinetics of light-induced charge separation and thermal charge recombination in donor-acceptor compounds, but quantum efficiencies have rarely been investigated. Here, we report on two essentially isomeric molecular triads, both comprising a π-extended tetrathiafulvalene (ExTTF) donor, a ruthenium(II)-based photosensitizer, and a naphthalene diimide (NDI) acceptor. The key difference between the two triads is how the NDI acceptor is connected. Linkage at the NDI core provides stronger electronic coupling to the other molecular components than connection via the nitrogen atoms of NDI. This change in molecular connectivity is expected to accelerate both energy-storing charge separation and energy-wasting charge recombination processes, but it is not a priori clear how this will affect the triad's ability to store photochemical energy; any gain resulting from faster charge separation could potentially be (over)compensated by losses through accelerated charge recombination. The new key insight emerging from our study is that the quantum yield for the formation of a long-lived charge-separated state increases by a factor of 5 when going from nitrogen- to core-connected NDI, providing the important proof of concept that better molecular connectivity indeed enables more efficient photochemical energy storage. The physical origin of this behavior seems to root in different orbital connectivity pathways for charge separation and charge recombination, as well as in differences in the relevant orbital interactions depending on NDI connection. Our work provides guidelines for how to discriminate between energy-storing and energy-wasting electron transfer reactions in order to improve the quantum yields for photochemical energy storage and solar energy conversion.
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Affiliation(s)
- Tobias
H. Bürgin
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, Basel 4056, Switzerland
| | - Tomohiro Ogawa
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, Basel 4056, Switzerland
- Graduate
School of Science and Engineering, University
of Toyama, Toyama 930-8555, Japan
| | - Oliver S. Wenger
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, Basel 4056, Switzerland
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3
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Kumar K, Wächtler M. Unravelling Dynamics Involving Multiple Charge Carriers in Semiconductor Nanocrystals. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:nano13091579. [PMID: 37177124 PMCID: PMC10181110 DOI: 10.3390/nano13091579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/02/2023] [Accepted: 05/04/2023] [Indexed: 05/15/2023]
Abstract
The use of colloidal nanocrystals as part of artificial photosynthetic systems has recently gained significant attention, owing to their strong light absorption and highly reproducible, tunable electronic and optical properties. The complete photocatalytic conversion of water to its components is yet to be achieved in a practically suitable and commercially viable manner. To complete this challenging task, we are required to fully understand the mechanistic aspects of the underlying light-driven processes involving not just single charge carriers but also multiple charge carriers in detail. This review focuses on recent progress in understanding charge carrier dynamics in semiconductor nanocrystals and the influence of various parameters such as dimension, composition, and cocatalysts. Transient absorption spectroscopic studies involving single and multiple charge carriers, and the challenges associated with the need for accumulation of multiple charge carriers to drive the targeted chemical reactions, are discussed.
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Affiliation(s)
- Krishan Kumar
- Department Functional Interfaces, Leibniz Institute of Photonic Technology Jena, Albert-Einstein-Straße 9, 07745 Jena, Germany
| | - Maria Wächtler
- Chemistry Department and State Research Center OPTIMAS, RPTU Kaiserslautern-Landau, Erwin-Schrödinger-Str. 52, 67663 Kaiserslautern, Germany
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4
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Bürgin TH, Glaser F, Wenger OS. Shedding Light on the Oxidizing Properties of Spin-Flip Excited States in a Cr III Polypyridine Complex and Their Use in Photoredox Catalysis. J Am Chem Soc 2022; 144:14181-14194. [PMID: 35913126 PMCID: PMC9376921 DOI: 10.1021/jacs.2c04465] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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The photoredox activity of well-known RuII complexes
stems from metal-to-ligand charge transfer (MLCT) excited states,
in which a ligand-based electron can initiate chemical reductions
and a metal-centered hole can trigger oxidations. CrIII polypyridines show similar photoredox properties, although they
have fundamentally different electronic structures. Their photoactive
excited state is of spin-flip nature, differing from the electronic
ground state merely by a change of one electron spin, but with otherwise
identical d-orbital occupancy. We find that the driving-force dependence
for photoinduced electron transfer from 10 different donors to a spin-flip
excited state of a CrIII complex is very similar to that
for a RuII polypyridine, and thereby validate the concept
of estimating the redox potential of d3 spin-flip excited
states in analogous manner as for the MLCT states of d6 compounds. Building on this insight, we use our CrIII complex for photocatalytic reactions not previously explored with
this compound class, including the aerobic bromination of methoxyaryls,
oxygenation of 1,1,2,2-tetraphenylethylene, aerobic hydroxylation
of arylboronic acids, and the vinylation of N-phenyl
pyrrolidine. This work contributes to understanding the fundamental
photochemical properties of first-row transition-metal complexes in
comparison to well-explored precious-metal-based photocatalysts.
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Affiliation(s)
- Tobias H Bürgin
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Felix Glaser
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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5
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Glaser F, Wenger OS. Red Light-Based Dual Photoredox Strategy Resembling the Z-Scheme of Natural Photosynthesis. JACS AU 2022; 2:1488-1503. [PMID: 35783177 PMCID: PMC9241018 DOI: 10.1021/jacsau.2c00265] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 05/11/2023]
Abstract
Photoredox catalysis typically relies on the use of single chromophores, whereas strategies, in which two different light absorbers are combined, are rare. In photosystems I and II of green plants, the two separate chromophores P680 and P700 both absorb light independently of one another, and then their excitation energy is combined in the so-called Z-scheme, to drive an overall reaction that is thermodynamically very demanding. Here, we adapt this concept to perform photoredox reactions on organic substrates with the combined energy input of two red photons instead of blue or UV light. Specifically, a CuI bis(α-diimine) complex in combination with in situ formed 9,10-dicyanoanthracenyl radical anion in the presence of excess diisopropylethylamine catalyzes ca. 50 dehalogenation and detosylation reactions. This dual photoredox approach seems useful because red light is less damaging and has a greater penetration depth than blue or UV radiation. UV-vis transient absorption spectroscopy reveals that the subtle change in solvent from acetonitrile to acetone induces a changeover in the reaction mechanism, involving either a dominant photoinduced electron transfer or a dominant triplet-triplet energy transfer pathway. Our study illustrates the mechanistic complexity in systems operating under multiphotonic excitation conditions, and it provides insights into how the competition between desirable and unwanted reaction steps can become more controllable.
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6
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Sinha N, Pfund B, Wegeberg C, Prescimone A, Wenger OS. Cobalt(III) Carbene Complex with an Electronic Excited-State Structure Similar to Cyclometalated Iridium(III) Compounds. J Am Chem Soc 2022; 144:9859-9873. [PMID: 35623627 PMCID: PMC9490849 DOI: 10.1021/jacs.2c02592] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Many organometallic
iridium(III) complexes have photoactive excited
states with mixed metal-to-ligand and intraligand charge transfer
(MLCT/ILCT) character, which form the basis for numerous applications
in photophysics and photochemistry. Cobalt(III) complexes with analogous
MLCT excited-state properties seem to be unknown yet, despite the
fact that iridium(III) and cobalt(III) can adopt identical low-spin
d6 valence electron configurations due to their close chemical
relationship. Using a rigid tridentate chelate ligand (LCNC), in which a central amido π-donor is flanked by two σ-donating
N-heterocyclic carbene subunits, we obtained a robust homoleptic complex
[Co(LCNC)2](PF6), featuring a photoactive
excited state with substantial MLCT character. Compared to the vast
majority of isoelectronic iron(II) complexes, the MLCT state of [Co(LCNC)2](PF6) is long-lived because it
does not deactivate as efficiently into lower-lying metal-centered
excited states; furthermore, it engages directly in photoinduced electron
transfer reactions. The comparison with [Fe(LCNC)2](PF6), as well as structural, electrochemical, and UV–vis
transient absorption studies, provides insight into new ligand design
principles for first-row transition-metal complexes with photophysical
and photochemical properties reminiscent of those known from the platinum
group metals.
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Affiliation(s)
- Narayan Sinha
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Björn Pfund
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Christina Wegeberg
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Alessandro Prescimone
- Department of Chemistry, University of Basel, BPR 1096, Mattenstrasse 24a, 4058 Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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7
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Fatima A, Rabah J, Allard E, Fensterbank H, Wright K, Burdzinski G, Clavier G, Sliwa M, Pino T, Méallet-Renault R, Steenkeste K, Ha-Thi MH. Selective population of triplet excited states in heavy-atom-free BODIPY-C 60 based molecular assemblies. Photochem Photobiol Sci 2022; 21:1573-1584. [PMID: 35612713 DOI: 10.1007/s43630-022-00241-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 05/02/2022] [Indexed: 12/14/2022]
Abstract
Photophysical studies on a BODIPY-fullerene-distyryl BODIPY triad (BDP-C60-DSBDP) and its reference dyads (BODIPY-fullerene; BDP-C60 and distyryl BODIPY-fullerene; DSBDP-C60) are presented herein. In the triad, the association of the two chromophore units linked by a fullerene moiety leads to strong near UV-Visible light absorption from 300 to 700 nm. The triplet-excited state was observed upon visible excitation in all these assemblies, and shown to be localized on the C60 or BODIPY moieties. Using quantitative nanosecond transient absorption, we provide a complete investigation on the lifetime and formation quantum yield of the triplet-excited state. In the BDP-C60 dyad, the triplet excited state of C60 (τ = 7 ± 1 μs) was obtained with a quantum yield of 40 ± 8%. For the DSBDP-C60 dyad and BDP-C60-DSBDP triad, a longer-lived triplet excited state with a lifetime of around 250 ± 20 μs centered on the DSBDP moiety was formed, with respective quantum yields of 37 ± 8 and 20 ± 4%. Triplet-triplet annihilation up-conversion is characterized in the BDP-C60 dyad and the bichromophoric triad in the presence of perylene and DSBDP-monomer as respective annihilators. The photo-induced formation of a long-lived 3DSBDP* in the triad coupled with panchromatic light absorption offers potential applications as a heavy-atom-free organic triplet photosensitizer.
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Affiliation(s)
- Anam Fatima
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France
| | - Jad Rabah
- Université Paris-Saclay, UVSQ, CNRS, Institut Lavoisier de Versailles, 78000, Versailles, France
| | - Emmanuel Allard
- Université Paris-Saclay, UVSQ, CNRS, Institut Lavoisier de Versailles, 78000, Versailles, France.
| | - Hélène Fensterbank
- Université Paris-Saclay, UVSQ, CNRS, Institut Lavoisier de Versailles, 78000, Versailles, France
| | - Karen Wright
- Université Paris-Saclay, UVSQ, CNRS, Institut Lavoisier de Versailles, 78000, Versailles, France
| | - Gotard Burdzinski
- Adam Mickiewicz Univ in Poznan, Fac Phys, Quantum Elect Lab, 61614, Poznan, Poland
| | - Gilles Clavier
- Université Paris-Saclay, ENS Paris-Saclay, CNRS, PPSM, 91190, Gif-sur-Yvette, France
| | - Michel Sliwa
- Univ. Lille, CNRS, UMR 8516, LASIRE, Laboratoire de Spectroscopie pour les Interactions, la Réactivité et l'Environnement, 59 000, Lille, France
| | - Thomas Pino
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France
| | - Rachel Méallet-Renault
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France.
| | - Karine Steenkeste
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France.
| | - Minh-Huong Ha-Thi
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France.
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8
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Ir(III)-Naphthoquinone complex as a platform for photocatalytic activity. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2022. [DOI: 10.1016/j.jpap.2021.100098] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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9
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Mims D, Herpich J, Lukzen NN, Steiner UE, Lambert C. Readout of spin quantum beats in a charge-separated radical pair by pump-push spectroscopy. Science 2021; 374:1470-1474. [PMID: 34914495 DOI: 10.1126/science.abl4254] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- David Mims
- Institute of Organic Chemistry, University of Würzburg, 97074 Würzburg, Germany
| | - Jonathan Herpich
- Institute of Organic Chemistry, University of Würzburg, 97074 Würzburg, Germany
| | - Nikita N Lukzen
- International Tomography Center and Novosibirsk State Universit, Novosibirsk 630090, Russia
| | - Ulrich E Steiner
- Department of Chemistry, University of Konstanz, 78464 Konstanz, Germany
| | - Christoph Lambert
- Institute of Organic Chemistry, University of Würzburg, 97074 Würzburg, Germany.,Center for Nanosystems Chemistry, University of Würzburg, 97074 Würzburg, Germany
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10
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Bürgin T, Wenger OS. Recent Advances and Perspectives in Photodriven Charge Accumulation in Molecular Compounds: A Mini Review. ENERGY & FUELS : AN AMERICAN CHEMICAL SOCIETY JOURNAL 2021; 35:18848-18856. [PMID: 35873109 PMCID: PMC9302442 DOI: 10.1021/acs.energyfuels.1c02073] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The formation of so-called solar fuels from abundant low-energetic compounds, such as carbon dioxide or water, relies on the chemical elementary steps of photoinduced electron transfer and accumulation of multiple redox equivalents. The majority of molecular systems explored to date require sacrificial electron donors to accumulate multiple electrons on a single acceptor unit, but the use of high-energetic sacrificial redox reagents is unsustainable. In recent years, an increasing number of molecular compounds for reversible light-driven accumulation of redox equivalents that do not need sacrificial electron donors has been reported. Those compounds are the focus of this mini review. Different concepts, such as redox potential compression (achieved by proton-coupled electron transfer, Lewis acid-base interactions, or structural rearrangements), hybrids with inorganic nanoparticles, and diffusion-controlled multi-component systems, will be discussed. Newly developed strategies to outcompete unproductive reaction pathways in favor of desired photoproduct formation will be compared, and the importance of identifying reaction intermediates in the course of multiphotonic excitation by different time-resolved spectroscopic techniques will be discussed. The mechanistic insights gained from molecular donor-photosensitizer-acceptor compounds inform the design of next-generation charge accumulation systems for solar energy conversion.
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11
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Neumann S, Wenger OS, Kerzig C. Controlling Spin-Correlated Radical Pairs with Donor-Acceptor Dyads: A New Concept to Generate Reduced Metal Complexes for More Efficient Photocatalysis. Chemistry 2021; 27:4115-4123. [PMID: 33274791 PMCID: PMC7986886 DOI: 10.1002/chem.202004638] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/02/2020] [Indexed: 12/30/2022]
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.
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Affiliation(s)
- Svenja Neumann
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Oliver S. Wenger
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Christoph Kerzig
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10—1455128MainzGermany
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12
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Kranz C, Wächtler M. Characterizing photocatalysts for water splitting: from atoms to bulk and from slow to ultrafast processes. Chem Soc Rev 2021; 50:1407-1437. [DOI: 10.1039/d0cs00526f] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This review provides a comprehensive overview on characterisation techniques for light-driven redox-catalysts highlighting spectroscopic, microscopic, electrochemical and spectroelectrochemical approaches.
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Affiliation(s)
- Christine Kranz
- Ulm University
- Institute of Analytical and Bioanalytical Chemistry
- 89081 Ulm
- Germany
| | - Maria Wächtler
- Leibniz Institute of Photonic Technology
- Department Functional Interfaces
- 07745 Jena
- Germany
- Friedrich Schiller University Jena
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13
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Schulz M, Hagmeyer N, Wehmeyer F, Lowe G, Rosenkranz M, Seidler B, Popov A, Streb C, Vos JG, Dietzek B. Photoinduced Charge Accumulation and Prolonged Multielectron Storage for the Separation of Light and Dark Reaction. J Am Chem Soc 2020; 142:15722-15728. [DOI: 10.1021/jacs.0c03779] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Martin Schulz
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
- Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany
| | - Nina Hagmeyer
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Frerk Wehmeyer
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Grace Lowe
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Marco Rosenkranz
- Leibniz Institute for Solid State and Materials Research, Helmholtzstraße 20, 01069 Dresden, Germany
| | - Bianca Seidler
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Alexey Popov
- Leibniz Institute for Solid State and Materials Research, Helmholtzstraße 20, 01069 Dresden, Germany
| | - Carsten Streb
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Johannes G. Vos
- SRC for Solar Energy Conversion, School of Chemical Sciences, Dublin City University, Dublin, Ireland
| | - Benjamin Dietzek
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
- Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany
- Centre for Energy and Environmental Chemistry (CEEC), Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena, Germany
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14
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Luo Y, Maloul S, Schönweiz S, Wächtler M, Streb C, Dietzek B. Yield-not only Lifetime-of the Photoinduced Charge-Separated State in Iridium Complex-Polyoxometalate Dyads Impact Their Hydrogen Evolution Reactivity. Chemistry 2020; 26:8045-8052. [PMID: 32237163 PMCID: PMC7383969 DOI: 10.1002/chem.202000982] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Indexed: 11/11/2022]
Abstract
Covalently linked photosensitizer-polyoxometalate (PS-POM) dyads are promising molecular systems for light-induced energy conversion processes, such as "solar" hydrogen generation. To date, very little is known of their fundamental photophysical properties which affect the catalytic reactivity and stability of the systems. PS-POM dyads often feature short-lived photoinduced charge-separated states, and the lifetimes of these states are considered crucial for the function of PS-POM dyads in molecular photocatalysis. Hence, strategies have been developed to extend the lifetimes of the photoinduced charge-separated states, either by tuning the PS photophysics or by tuning the POM redox properties. Recently, some of us reported PS-POM dyads based on cyclometalated IrIII complexes covalently linked to Anderson-type polyoxometalate. Distinct hydrogen evolution reactivity (HER) of the dyads was observed, which was tuned by varying the central metal ion M of the POMM (M=Mn3+ , Co3+ , Fe3+ ). In this manuscript, the photoinduced electron-transfer processes in the three Ir-POMM dyads are investigated to rationalize the underlying reasons for the differences in HER activity observed. We report that upon excitation of the IrIII complex, ultrafast (sub-ps) charge separation occurs, leading to different amounts of the charge-separated states (Ir.+ -POMM .- ) generated in the different dyads. However, in all dyads studied, the resulting Ir.+ -POMM .- species are short-lived (sub-ns) when compared to reference electron acceptors (e.g. porphyrins or fullerenes) reported in the literature. The reductive quenching of Ir.+ -POMM .- by a sacrificial donor, triethyl amine (1 m), to generate the intermediate Ir-POMM .- is estimated to be very efficient (70-80 %) for all dyads studied. Based on this analyses, we conclude that the yield instead of the lifetime of the Ir.+ -POMM .- charge-separated state determines the catalytic capacity of the dyads investigated. This new feature in the PS-POM photophysics could lead to new design criteria for the development of novel PS-POM dyads.
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Affiliation(s)
- Yusen Luo
- Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743, Jena, Germany.,Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Strasse 9, 07745, Jena, Germany
| | - Salam Maloul
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Stefanie Schönweiz
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Maria Wächtler
- Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743, Jena, Germany.,Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Strasse 9, 07745, Jena, Germany
| | - Carsten Streb
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Benjamin Dietzek
- Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743, Jena, Germany.,Department Functional Interfaces, Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Strasse 9, 07745, Jena, Germany.,Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich-Schiller-University Jena, Philosophenweg 7a, 07743, Jena, Germany
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Glaser F, Kerzig C, Wenger OS. Multiphotonen‐Anregung in der Photoredoxkatalyse: Konzepte, Anwendungen und Methoden. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201915762] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Felix Glaser
- Departement Chemie Universität Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | - Christoph Kerzig
- Departement Chemie Universität Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | - Oliver S. Wenger
- Departement Chemie Universität Basel St. Johanns-Ring 19 4056 Basel Schweiz
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16
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Glaser F, Kerzig C, Wenger OS. Multi-Photon Excitation in Photoredox Catalysis: Concepts, Applications, Methods. Angew Chem Int Ed Engl 2020; 59:10266-10284. [PMID: 31945241 DOI: 10.1002/anie.201915762] [Citation(s) in RCA: 183] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/16/2020] [Indexed: 01/28/2023]
Abstract
The energy of visible photons and the accessible redox potentials of common photocatalysts set thermodynamic limits to photochemical reactions that can be driven by traditional visible-light irradiation. UV excitation can be damaging and induce side reactions, hence visible or even near-IR light is usually preferable. Thus, photochemistry currently faces two divergent challenges, namely the desire to perform ever more thermodynamically demanding reactions with increasingly lower photon energies. The pooling of two low-energy photons can address both challenges simultaneously, and whilst multi-photon spectroscopy is well established, synthetic photoredox chemistry has only recently started to exploit multi-photon processes on the preparative scale. Herein, we have a critical look at currently developed reactions and mechanistic concepts, discuss pertinent experimental methods, and provide an outlook into possible future developments of this rapidly emerging area.
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Affiliation(s)
- Felix Glaser
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Christoph Kerzig
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
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17
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Kerzig C, Wenger OS. Reactivity control of a photocatalytic system by changing the light intensity. Chem Sci 2019; 10:11023-11029. [PMID: 32206254 PMCID: PMC7069242 DOI: 10.1039/c9sc04584h] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 10/08/2019] [Indexed: 12/13/2022] Open
Abstract
By using simple optics such as a lens, switching between one- and two-photon driven reaction mechanisms became feasible, which allows the control over the main products of photochemical reactions.
We report a novel light-intensity dependent reactivity approach allowing us to selectively switch between triplet energy transfer and electron transfer reactions, or to regulate the redox potential available for challenging reductions. Simply by adjusting the light power density with an inexpensive lens while keeping all other parameters constant, we achieved control over one- and two-photon mechanisms, and successfully exploited our approach for lab-scale photoreactions using three substrate classes with excellent selectivities and good product yields. Specifically, our proof-of-concept study demonstrates that the irradiation intensity can be used to control (i) the available photoredox reactivity for reductive dehalogenations to selectively target either bromo- or chloro-substituted arenes, (ii) the photochemical cis–trans isomerization of olefins versus their photoreduction, and (iii) the competition between hydrogen atom abstraction and radical dimerization processes.
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Affiliation(s)
- Christoph Kerzig
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland . ;
| | - Oliver S Wenger
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland . ;
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