1
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Bryden MA, Crovini E, Comerford T, Studer A, Zysman-Colman E. Organic Donor-Acceptor Thermally Activated Delayed Fluorescence Photocatalysts in the Photoinduced Dehalogenation of Aryl Halides. Angew Chem Int Ed Engl 2024; 63:e202405081. [PMID: 38600037 DOI: 10.1002/anie.202405081] [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: 03/14/2024] [Revised: 04/02/2024] [Accepted: 04/10/2024] [Indexed: 04/12/2024]
Abstract
We report a family of donor-acceptor thermally activated delayed fluorescent (TADF) compounds based on derivatives of DMAC-TRZ, that are strongly photoreducing. Both Eox and thus E*ox could be tuned via substitution of the DMAC donor with a Hammett series of p-substituted phenyl moieties while Ered remained effectively constant. These compounds were assessed in the photoinduced dehalogenation of aryl halides, and analogues bearing electron withdrawing groups were found to produce the highest yields. Substrates of up to Ered=-2.72 V could be dehalogenated at low PC loading (1 mol %) and under air, conditions much milder than previously reported for this reaction. Spectroscopic and chemical studies demonstrate that all PCs, including literature reference PCs, photodegrade, and that it is these photodegradation products that are responsible for the reactivity.
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Affiliation(s)
- Megan Amy Bryden
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, United Kingdom
| | - Ettore Crovini
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, United Kingdom
| | - Thomas Comerford
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, United Kingdom
| | - Armido Studer
- Organisch-Chemisches Institut, University of Münster, Corrensstaße 40, 48149, Münster, Germany
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, United Kingdom
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2
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Märsch J, Reiter S, Rittner T, Rodriguez-Lugo RE, Whitfield M, Scott DJ, Kutta RJ, Nuernberger P, de Vivie-Riedle R, Wolf R. Cobalt-Mediated Photochemical C-H Arylation of Pyrroles. Angew Chem Int Ed Engl 2024:e202405780. [PMID: 38693673 DOI: 10.1002/anie.202405780] [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: 03/25/2024] [Revised: 04/26/2024] [Accepted: 04/29/2024] [Indexed: 05/03/2024]
Abstract
Precious metal complexes remain ubiquitous in photoredox catalysis (PRC) despite concerted efforts to find more earth-abundant catalysts and replacements based on 3d metals in particular. Most otherwise plausible 3d metal complexes are assumed to be unsuitable due to short-lived excited states, which has led researchers to prioritize the pursuit of longer excited-state lifetimes through careful molecular design. However, we report herein that the C-H arylation of pyrroles and related substrates (which are benchmark reactions for assessing the efficacy of photoredox catalysts) can be achieved using a simple and readily accessible octahedral bis(diiminopyridine) cobalt complex, [1-Co](PF6)2. Notably, [1-Co]2+ efficiently functionalizes both chloro- and bromoarene substrates despite the short excited-state lifetime of the key photoexcited intermediate *[1-Co]2+ (8 ps). We present herein the scope of this C-H arylation protocol and provide mechanistic insights derived from detailed spectroscopic and computational studies. These indicate that, despite its transient existence, reduction of *[1-Co]2+ is facilitated via pre-assembly with the NEt3 reductant, highlighting an alternative strategy for the future development of 3d metal-catalyzed PRC.
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Affiliation(s)
- Julia Märsch
- Institute of Inorganic Chemistry, University of Regensburg, 93040, Regensburg, Germany
| | - Sebastian Reiter
- Department of Chemistry, Ludwig Maximilian University Munich, 81377, Munich, Germany
| | - Thomas Rittner
- Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040, Regensburg, Germany
| | - Rafael E Rodriguez-Lugo
- Institute of Inorganic Chemistry, University of Regensburg, 93040, Regensburg, Germany
- present address: Istituto di Chimica dei Composti Organometallici, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, Sesto Fiorentino, 50019, Italy
| | - Maximilian Whitfield
- Department of Chemistry, Ludwig Maximilian University Munich, 81377, Munich, Germany
| | - Daniel J Scott
- Institute of Inorganic Chemistry, University of Regensburg, 93040, Regensburg, Germany
- present address: Department of Chemistry, University of Bath, Claverton Down Bath, BA2 7AY, United Kingdom
| | - Roger Jan Kutta
- Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040, Regensburg, Germany
| | - Patrick Nuernberger
- Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040, Regensburg, Germany
| | | | - Robert Wolf
- Institute of Inorganic Chemistry, University of Regensburg, 93040, Regensburg, Germany
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3
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Shen D, Li L, Ren T, Chen K, Zhang X, Zhang H, Zhang S, Gong P, Zhang F, Chao M. Radical-Smiles Rearrangement by a Vitamin B2-Derived Photocatalyst in Water. J Org Chem 2024; 89:2691-2702. [PMID: 38277486 DOI: 10.1021/acs.joc.3c02762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2024]
Abstract
Herein, we report a catalytic radical-Smiles rearrangement system of arene migration from ether to carboxylic acid with riboflavin tetraacetate (RFT), a readily available ester of natural vitamin B2, as the photocatalyst and water as a green solvent, being free of external oxidant, base, metal, inert gas protection, and lengthy reaction time. Not only the known substituted 2-phenyloxybenzoic acids substrates but also a group of naphthalene- and heterocycle-based analogues was converted to the corresponding aryl salicylates for the first time. Mechanistic studies, especially a couple of kinetic isotope effect (KIE) experiments, suggested a sequential electron transfer-proton transfer processes enabled by the bifunctional flavin photocatalyst.
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Affiliation(s)
- Duyi Shen
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Linghui Li
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Ting Ren
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Kaihui Chen
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Xuan Zhang
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Haixing Zhang
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Shumiao Zhang
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Peiwei Gong
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Fanjun Zhang
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
| | - Mianran Chao
- Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China
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4
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Zubova E, Pokluda A, Dvořáková H, Krupička M, Cibulka R. Exploring the Reactivity of Flavins with Nucleophiles Using a Theoretical and Experimental Approach. Chempluschem 2023:e202300547. [PMID: 38064649 DOI: 10.1002/cplu.202300547] [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: 09/29/2023] [Revised: 11/30/2023] [Indexed: 01/13/2024]
Abstract
Covalent adducts of flavin cofactors with nucleophiles play an important role in non-canonical function of flavoenzymes as well as in flavin-based catalysis. Herein, the interaction of flavin derivatives including substituted flavins (isoalloxazines), 1,10-ethylene-bridged flavinium salts, and non-substituted alloxazine and deazaflavin with selected nucleophiles was investigated using an experimental and computational approach. Triphenylphosphine or trimethylphosphine, 1-nitroethan-1-ide, and methoxide were selected as representatives of neutral soft, anionic soft, and hard nucleophiles, respectively. The interactions were investigated using UV/Vis and 1 H NMR spectroscopy as well as by DFT calculations. The position of nucleophilic attack estimated using the calculated Gibbs free energy values was found to correspond with the experimental data, favouring the addition of phosphine and 1-nitroethan-1-ide into position N(5) and methoxide into position C(10a) of 1,10-ethylene-bridged flavinium salts. The calculated Gibbs free energy values were found to correlate with the experimental redox potentials of the flavin derivatives tested. These findings can be utilized as valuable tools for the design of artificial flavin-based catalytic systems or investigating the mechanism of flavoenzymes.
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Affiliation(s)
- Ekaterina Zubova
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Adam Pokluda
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Hana Dvořáková
- Central Laboratories, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Martin Krupička
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Radek Cibulka
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic
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5
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Wörner J, Panter S, Illarionov B, Bacher A, Fischer M, Weber S. Expanding Reaction Horizons: Evidence of the 5-Deazaflavin Radical Through Photochemically Induced Dynamic Nuclear Polarization. Angew Chem Int Ed Engl 2023; 62:e202309334. [PMID: 37571931 DOI: 10.1002/anie.202309334] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/09/2023] [Accepted: 08/10/2023] [Indexed: 08/13/2023]
Abstract
Deazaflavins are important analogues of the naturally occurring flavins: riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). The use of 5-deazaflavin as a replacement coenzyme in a number of flavoproteins has proven particularly valuable in unraveling and manipulating their reaction mechanisms. It was frequently reported that one-electron-transfer reactions in flavoproteins are impeded with 5-deazaflavin as the cofactor. Based on these findings, it was concluded that the 5-deazaflavin radical is significantly less stable compared to the respective flavin semiquinone and quickly re-oxidizes or undergoes disproportionation. The long-standing paradigm of 5-deazaflavin being solely a two-electron/hydride acceptor/donor-"a nicotinamide in flavin clothing"-needs to be re-evaluated now with the indirect observation of a one-electron-reduced (paramagnetic) species using photochemically induced dynamic nuclear polarization (photo-CIDNP) 1 H nuclear magnetic resonance (NMR) under biologically relevant conditions.
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Affiliation(s)
- Jakob Wörner
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Sabrina Panter
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Boris Illarionov
- Institut für Lebensmittelchemie, Universität Hamburg, Grindelallee 117, 20146, Hamburg, Germany
| | - Adelbert Bacher
- TUM School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, 85747, Garching, Germany
| | - Markus Fischer
- Institut für Lebensmittelchemie, Universität Hamburg, Grindelallee 117, 20146, Hamburg, Germany
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
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6
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Horsewill S, Hierlmeier G, Farasat Z, Barham JP, Scott DJ. Shining Fresh Light on Complex Photoredox Mechanisms through Isolation of Intermediate Radical Anions. ACS Catal 2023; 13:9392-9403. [PMID: 37497378 PMCID: PMC10367049 DOI: 10.1021/acscatal.3c02515] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 06/20/2023] [Indexed: 07/28/2023]
Abstract
Photoredox catalysis (PRC) has gained enormous and wide-ranging interest in recent years but has also been subject to significant mechanistic uncertainty, even controversy. To provide a method by which the missing understanding can begin to be filled in, we demonstrate herein that it is possible to isolate as authentic materials the one-electron reduction products of representative PRC catalysts (PCs). Specifically, KC8 reduction of both 9,10-dicyanoanthracene and a naphthalene monoamide derivative in the presence of a cryptand provides convenient access to the corresponding [K(crypt)+][PC·-] salts as clean materials that can be fully characterized by techniques including EPR and XRD. Because PC·- states are key intermediates in PRC reactions, such isolation allows for highly controlled study of these anions' specific reactivity and hence their mechanistic roles. As a demonstration of this principle, we show that these salts can be used to conveniently interrogate the mechanisms of recent, high-profile "conPET" and "e-PRC" reactions, which are currently the subject of both significant interest and acute controversy. Using very simple experiments, we are able to provide striking insights into these reactions' underlying mechanisms and to observe surprising levels of hidden complexity that would otherwise have been very challenging to identify and that emphasize the care and control that are needed when interrogating and interpreting PRC mechanisms. These studies provide a foundation for the study of a far broader range of questions around conPET, e-PRC, and other PRC reaction mechanisms in the future, using the same strategy of PC·- isolation.
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Affiliation(s)
- Samuel
J. Horsewill
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Gabriele Hierlmeier
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Zahra Farasat
- Professor
Rashidi Laboratory of Organometallic Chemistry, Department of Chemistry,
College of Sciences, Shiraz University, Shiraz, Fars 71467-13565, Iran
| | - Joshua P. Barham
- Institute
of Organic Chemistry, University of Regensburg, Universitätsstr. 31, Regensburg, Bayern 93053, Germany
| | - Daniel J. Scott
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
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7
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Čubiňák M, Varma N, Oeser P, Pokluda A, Pavlovska T, Cibulka R, Sikorski M, Tobrman T. Tuning the Photophysical Properties of Flavins by Attaching an Aryl Moiety via Direct C-C Bond Coupling. J Org Chem 2023; 88:218-229. [PMID: 36525315 DOI: 10.1021/acs.joc.2c02168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Palladium-catalyzed Suzuki reactions of brominated flavin derivatives (5-deazaflavins, alloxazines, and isoalloxazines) with boronic acids or boronic acid esters that occur readily under mild conditions were shown to be an effective tool for the synthesis of a broad range of 7/8-arylflavins. In general, the introduction of an aryl/heteroaryl group by means of a direct C-C bond has been shown to be a promising approach to tuning the photophysical properties of flavin derivatives. The aryl substituents caused a bathochromic shift in the absorption spectra of up to 52 nm and prolonged the fluorescence lifetime by up to 1 order of magnitude. Moreover, arylation of flavin derivatives decreased their ability to generate singlet oxygen.
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Affiliation(s)
- Marek Čubiňák
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28Prague 6, Czech Republic
| | - Naisargi Varma
- Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614Poznań, Poland
| | - Petr Oeser
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28Prague 6, Czech Republic
| | - Adam Pokluda
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28Prague 6, Czech Republic
| | - Tetiana Pavlovska
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28Prague 6, Czech Republic
| | - Radek Cibulka
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28Prague 6, Czech Republic
| | - Marek Sikorski
- Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614Poznań, Poland
| | - Tomáš Tobrman
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28Prague 6, Czech Republic
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