Recent Advances in Photoredox Catalysts

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (20 November 2021) | Viewed by 28681

Special Issue Editors


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Centre National de la Recherche Scientifique (CNRS), Universite de Haute-Alsace (UHA), UMR 7361, IS2M, 15 Rue Jean Starcky, F-68057 Mulhouse, France
Interests: photopolymerization; photochemistry; polymers and lights; photoinitiators; 3D printing (stereolithography)
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Special Issue Information

Dear Colleagues,

With the emphasis on resource and energy conservation as well as environmental issues, there has been a move towards chemical processes that can be carried out under safer conditions. These issues can be addressed by photoredox catalysis. While photoredox catalysis was initially developed for organic chemistry, this unprecedented approach is now being applied to various research fields, ranging from the synthesis of polymers to water depollution or the functionalization of metal surfaces, etc. Using this approach, a drastic reduction of catalyst content could be achieved, resulting from the possibility of regenerating the latter in situ.

Researchers in the field are cordially invited to submit relevant manuscripts concerning the development of new photoredox catalysts for a Special Issue entitled ‘Recent Advances in Photoredox Catalysts’, within the journal Catalysts. Perspectives and reviews in this active research field are also welcome.

Dr. Frédéric Dumur
Prof. Dr. Jacques Lalevée
Guest Editors

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Keywords

  • photoredox catalysts
  • organocatalysts
  • metal complexes

Published Papers (7 papers)

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Editorial

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5 pages, 212 KiB  
Editorial
Recent Advances in Photoredox Catalysts
by Frédéric Dumur and Jacques Lalevée
Catalysts 2024, 14(1), 26; https://doi.org/10.3390/catal14010026 - 28 Dec 2023
Viewed by 1069
Abstract
Photoredox catalysis constitutes a flourishing and fascinating field of organic chemistry, enabling the efficient construction of a variety of non-traditional bonds [...] Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)

Research

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28 pages, 24869 KiB  
Article
Thioxanthone Derivatives as a New Class of Organic Photocatalysts for Photopolymerisation Processes and the 3D Printing of Photocurable Resins under Visible Light
by Emilia Hola, Maciej Pilch and Joanna Ortyl
Catalysts 2020, 10(8), 903; https://doi.org/10.3390/catal10080903 - 08 Aug 2020
Cited by 26 | Viewed by 5049
Abstract
In the present paper, novel thioxanthone-based compounds were synthesised and evaluated as a component of photoredox catalysts/photoinitiating systems for the free-radical polymerisation (FRP) of acrylates and the ring-opening cationic polymerisation (CP) of epoxy monomers. The performance of the obtained thioxanthones in two- and [...] Read more.
In the present paper, novel thioxanthone-based compounds were synthesised and evaluated as a component of photoredox catalysts/photoinitiating systems for the free-radical polymerisation (FRP) of acrylates and the ring-opening cationic polymerisation (CP) of epoxy monomers. The performance of the obtained thioxanthones in two- and three-component photoinitiating systems, in combination with amines, iodonium or sulphonium salt, as well as with alkyl halide, for photopolymerisation processes upon exposure to light emitting diodes (LEDs) with a maximum emission of 405 nm and 420 nm, was investigated. The studied compounds act also as one-component free-radical photoinitiators. Fourier transform real-time infrared spectroscopy was used to monitor the kinetics of disappearance of the functional groups of the monomers during photoinitiated polymerisation. Excellent photoinitiating efficiency and high final conversions of functional groups were observed. Moreover, the influence of thioxanthone skeleton substitution on photoinitiating efficiency was discussed. The photochemical mechanism was also investigated through cyclic voltammetry. It was discovered that thioxanthone derivatives can be used as a metal-free photoredox catalyst active for both oxidative and reductive cycles. Furthermore, a photopolymerizable system based on novel thioxanthone derivatives in a stereolithography three-dimensional (3D) printing technology under visible sources of light was used. The effects of photoinitiator type system and monomer type in photoresins during 3D printing processes were explored. The outcome of this research is the development of high-performance visible photosensitive resins with improved photosensitivity obtained thanks to the development of entirely novel photoinitiating systems specifically adapted for this application. Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)
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30 pages, 17614 KiB  
Article
Photochemical Study of a New Bimolecular Photoinitiating System for Vat Photopolymerization 3D Printing Techniques under Visible Light
by Paweł Fiedor, Maciej Pilch, Patryk Szymaszek, Anna Chachaj-Brekiesz, Mariusz Galek and Joanna Ortyl
Catalysts 2020, 10(3), 284; https://doi.org/10.3390/catal10030284 - 02 Mar 2020
Cited by 39 | Viewed by 4505
Abstract
In this work, we presented a new bimolecular photoinitiating system based on 2-amino-4,6-diphenylpyridine-3-carbonitrile derivatives as visible photosensitizers of diphenyliodonium salt. Real-time FTIR and photo-DSC photopolymerization experiments with a cycloaliphatic epoxide and vinyl monomers showed surprisingly good reactivity of the bimolecular photoinitiating systems under [...] Read more.
In this work, we presented a new bimolecular photoinitiating system based on 2-amino-4,6-diphenylpyridine-3-carbonitrile derivatives as visible photosensitizers of diphenyliodonium salt. Real-time FTIR and photo-DSC photopolymerization experiments with a cycloaliphatic epoxide and vinyl monomers showed surprisingly good reactivity of the bimolecular photoinitiating systems under UV-A, as well as under visible light sources. Steady-state photolysis, fluorescence experiments, theoretical calculations of molecular orbitals, and electrochemical analysis demonstrated photo-redox behavior as well as the ability to form initiating species via photo-reduction or photo-oxidation pathways, respectively. Therefore, the 2-amino-4,6-diphenylpyridine-3-carbonitrile derivatives were also investigated as a type II free-radical photoinitiator with amine. It was confirmed that the 2-amino-4,6-diphenylpyridine-3-carbonitrile derivatives, in combination with different types of additives, e.g., amine as a co-initiator or the presence of onium salt, can act as bimolecular photoinitiating systems for cationic, free-radical, and thiol-ene photopolymerization processes by hydrogen abstraction and/or electron transfer reactions stimulated by either near-UV or visible light irradiation. Finally, the 2-amino-4,6-diphenylpyridine-3-carbonitrile derivatives were selected for 3D printing rapid prototyping experiments. Test objects were successfully printed using purely cationic photosensitive resin, created on a 3D printer with a visible LED light source. Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)
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27 pages, 6397 KiB  
Article
Development of New High-Performance Biphenyl and Terphenyl Derivatives as Versatile Photoredox Photoinitiating Systems and Their Applications in 3D Printing Photopolymerization Processes
by Wiktoria Tomal, Maciej Pilch, Anna Chachaj-Brekiesz and Joanna Ortyl
Catalysts 2019, 9(10), 827; https://doi.org/10.3390/catal9100827 - 01 Oct 2019
Cited by 18 | Viewed by 4497
Abstract
Novel 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were proposed as photosensitizes of iodonium salt for a highly effective bimolecular photoinitiating system upon soft irradiation conditions under long-wave ultraviolet (UV-A) and visible light. Remarkably, these structures are highly versatile, allowing access to photoinitiating systems for the free-radical polymerization [...] Read more.
Novel 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were proposed as photosensitizes of iodonium salt for a highly effective bimolecular photoinitiating system upon soft irradiation conditions under long-wave ultraviolet (UV-A) and visible light. Remarkably, these structures are highly versatile, allowing access to photoinitiating systems for the free-radical polymerization of acrylates, the cationic photopolymerization of epoxides, glycidyl, and vinyl ethers, the synthesis of interpenetrated polymer networks (IPNs) and the thiol-ene photopolymerization processes. Excellent polymerization profiles for all of the monomers, along with the high final conversions, were obtained. The initiation mechanisms of these bimolecular systems based on the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were investigated using the real-time FT-IR technique, steady-state photolysis, fluorescence experiments, theoretical calculations of molecular orbitals, and electrochemical analysis. Moreover, the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were investigated as a type II free-radical photoinitiator with amine. It was confirmed that the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives, in combination with different types of additives, e.g., amine as co-initiator or in the presence of onium salt, can act as a bimolecular photoinitiating system via the photo-reduction or photo-oxidation pathways, respectively. Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)
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20 pages, 7202 KiB  
Article
New 1,8-Naphthalimide Derivatives as Photoinitiators for Free-Radical Polymerization Upon Visible Light
by Aude-Héloïse Bonardi, Soraya Zahouily, Céline Dietlin, Bernadette Graff, Fabrice Morlet-Savary, Malika Ibrahim-Ouali, Didier Gigmes, Norbert Hoffmann, Frédéric Dumur and Jacques Lalevée
Catalysts 2019, 9(8), 637; https://doi.org/10.3390/catal9080637 - 26 Jul 2019
Cited by 41 | Viewed by 4591
Abstract
Photopolymerization processes, and especially those carried out under visible light, are more and more widespread for their multiple advantages compared to thermal processes. In the present paper, new 1,8-naphthalimide derivatives are proposed as photoinitiators for free-radical polymerization upon visible light exposure using light-emitting [...] Read more.
Photopolymerization processes, and especially those carried out under visible light, are more and more widespread for their multiple advantages compared to thermal processes. In the present paper, new 1,8-naphthalimide derivatives are proposed as photoinitiators for free-radical polymerization upon visible light exposure using light-emitting diodes (LEDs) at 395, 405, and 470 nm. These photoinitiators are used in combination with both iodonium salts and phosphine. The synthesis of these compounds as well as their excellent polymerization initiation ability for methacrylate monomers are presented in this article. A full picture of the involved chemical mechanisms is also provided thanks to photolysis, radical characterization, and redox measurements. Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)
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Review

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14 pages, 3737 KiB  
Review
Advances in Homogeneous Photocatalytic Organic Synthesis with Colloidal Quantum Dots
by Dan-Yan Wang, Yu-Yun Yin, Chuan-Wei Feng, Rukhsana and Yong-Miao Shen
Catalysts 2021, 11(2), 275; https://doi.org/10.3390/catal11020275 - 18 Feb 2021
Cited by 16 | Viewed by 3330
Abstract
Colloidal semiconductor quantum dots (QDs) have been proven to be excellent photocatalysts due to their high photostability, large extinction coefficients, and tunable optoelectrical properties, and have attracted extensive attention by synthetic chemists. These excellent properties demonstrate its promise in the field of photocatalysis. [...] Read more.
Colloidal semiconductor quantum dots (QDs) have been proven to be excellent photocatalysts due to their high photostability, large extinction coefficients, and tunable optoelectrical properties, and have attracted extensive attention by synthetic chemists. These excellent properties demonstrate its promise in the field of photocatalysis. In this review, we summarize the recent application of QDs as homogeneous catalysts in various photocatalytic organic reactions. These meaningful works in organic transformations show the unique catalytic activity of quantum dots, which are different from other semiconductors. Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)
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38 pages, 25382 KiB  
Review
Recent Advances on Copper Complexes as Visible Light Photoinitiators and (Photo) Redox Initiators of Polymerization
by Guillaume Noirbent and Frédéric Dumur
Catalysts 2020, 10(9), 953; https://doi.org/10.3390/catal10090953 - 20 Aug 2020
Cited by 35 | Viewed by 4555
Abstract
Metal complexes are used in numerous chemical and photochemical processes in organic chemistry. Metal complexes have not been excluded from the interest of polymerists to convert liquid resins into solid materials. If iridium complexes have demonstrated their remarkable photochemical reactivity in polymerization, their [...] Read more.
Metal complexes are used in numerous chemical and photochemical processes in organic chemistry. Metal complexes have not been excluded from the interest of polymerists to convert liquid resins into solid materials. If iridium complexes have demonstrated their remarkable photochemical reactivity in polymerization, their high costs and their attested toxicities have rapidly discarded these complexes for further developments. Conversely, copper complexes are a blooming field of research in (photo) polymerization due to their low cost, easy syntheses, long-living excited state lifetimes, and their remarkable chemical and photochemical stabilities. Copper complexes can also be synthesized in solution and by mechanochemistry, paving the way towards the synthesis of photoinitiators by Green synthetic approaches. In this review, an overview of the different copper complexes reported to date is presented. Copper complexes are versatile candidates for polymerization, as these complexes are now widely used not only in photopolymerization, but also in redox and photoassisted redox polymerization processes. Full article
(This article belongs to the Special Issue Recent Advances in Photoredox Catalysts)
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