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Catalysts
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Free Radicals in Catalysis, Organic Synthesis, and Material Science
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Free Radicals in Catalysis, Organic Synthesis, and Material Science

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalysis in Organic and Polymer Chemistry".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 8292

Special Issue Editors

Dr. Igor Krylov

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Guest Editor
N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia
Interests: photoredox-catalysis; redox-organocatalysis; chemistry of free radicals; organic synthesis; crop protection
Prof. Dr. Alexander O. Terent'ev

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Guest Editor
N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences (RAS), Leninsky Prospect, 47 119991 Moscow, Russia
Interests: transition metal catalysis; homogeneous and heterogeneous catalysis in oxidation reactions; direct and indirect electroorganic synthesis; oxidative coupling reactions; reactions with C-, O-, and S-centered radicals; chemistry of peroxides; compounds with antiparasitic, cytotoxic, and antimicrobial activity; agrochemistry
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Evgeny Tretyakov

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Guest Editor
N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia
Interests: organic chemistry & molecular magnetism; functionally oriented synthesis of organic radicals; design of magnetically active heterospin systems; synthesis of fluorinated heterocycles and quinones
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the last decade, we have observed the rapid development of radical-mediated selective processes in organic synthesis and catalysis, photochemistry and electrochemistry, synthesis and modification of polymer materials, energy storage, and transformation. The fundamentally different reactivity of free radicals compared to diamagnetic species makes them useful and sometimes irreplaceable tools for organic synthesis. Free radicals play an important role in catalytic processes as reactive intermediates generated from substrates or catalytically active species. The interest in free radicals was also stimulated by the intensive development of photoredox-catalysis under visible light and organic electrochemistry — fundamental green approaches to drive redox processes in an energy-efficient manner at mild temperature conditions and avoiding toxic reagents. In both photoredox-catalyzed and electrochemical reactions, the single electron transfer is a common key step, which produces reactive radical species from diamagnetic compounds.

The Special Issue, “Free Radicals in Catalysis, Organic Synthesis, and Material Science”, invites original research papers and reviews devoted to catalytic processes involving radicals (organic free radicals and ion-radicals, heteroatom-centered radicals, and inorganic radical species) as key intermediates, including following main topics (but not limited to):

  • Photoredox catalysis involving free-radical species in organic synthesis, small molecule transformations, and the decomposition of pollutants;
  • Development of electrocatalytic processes involving free radicals;
  • Homogeneous and heterogeneous catalytic systems employing radical species;
  • Radical chain processes;
  • Living radical polymerization mediated by organic free; radicals and/or transition metal complexes;
  • Stability and reactivity of free radicals—key intermediates in catalytic processes.

Dr. Igor Krylov
Prof. Dr. Alexander O. Terent'ev
Prof. Dr. Evgeny Tretyakov
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • photoredox-catalysis
  • electrocatalysis
  • single-electron transfer
  • atom transfer
  • radical CH-functionalization, radical addition
  • redox-active molecules
  • living polymerization

Published Papers (7 papers)

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Research

13 pages, 1582 KiB  
Article
CCl4-TMEDA-CuCl—A Novel Convenient Catalytic System for Dimerization of Terminal Acetylenes in Mild Conditions
by Vasiliy M. Muzalevskiy, Alexey V. Shastin, Sarvinoz I. Tirkasheva, Odiljon E. Ziyadullaev, Askar B. Parmanov and Valentine G. Nenajdenko
Catalysts 2023, 13(10), 1330; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13101330 - 28 Sep 2023
Viewed by 1055
Abstract
A novel catalytic system for homocoupling terminal acetylenes was elaborated based on CuCl as a catalyst (10 mol%), TMEDA as a base and CCl4 as an oxidant. The influence of the solvent, base, amount of catalyst and CCl4 on the reaction [...] Read more.
A novel catalytic system for homocoupling terminal acetylenes was elaborated based on CuCl as a catalyst (10 mol%), TMEDA as a base and CCl4 as an oxidant. The influence of the solvent, base, amount of catalyst and CCl4 on the reaction was investigated. Methanol was found to be the solvent of choice. The broad synthetic scope of the reaction was demonstrated. Diynes with various substituents were prepared in up to 92% yields. The possible reaction mechanism is discussed. Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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15 pages, 3824 KiB  
Article
Redox Chemistry of Pt(II) Complex with Non-Innocent NHC Bis(Phenolate) Pincer Ligand: Electrochemical, Spectroscopic, and Computational Aspects
by Ilya K. Mikhailov, Zufar N. Gafurov, Alexey A. Kagilev, Vladimir I. Morozov, Artyom O. Kantyukov, Ekaterina M. Zueva, Gumar R. Ganeev, Ilyas F. Sakhapov, Asiya V. Toropchina, Igor A. Litvinov, Galina A. Gurina, Alexander A. Trifonov, Oleg G. Sinyashin and Dmitry G. Yakhvarov
Catalysts 2023, 13(9), 1291; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13091291 - 11 Sep 2023
Cited by 2 | Viewed by 1028
Abstract
A Pt(II) complex bearing chelating tridentate bis-aryloxide tetrahydropyrimidinium-based N-heterocyclic carbene (NHC) was synthesized and characterized by using different techniques. Both cyclic voltammetry and differential pulse voltammetry were used to study the electrochemical properties of the complex, revealing two reversible one-electron oxidation processes. The [...] Read more.
A Pt(II) complex bearing chelating tridentate bis-aryloxide tetrahydropyrimidinium-based N-heterocyclic carbene (NHC) was synthesized and characterized by using different techniques. Both cyclic voltammetry and differential pulse voltammetry were used to study the electrochemical properties of the complex, revealing two reversible one-electron oxidation processes. The chemical generation and isolation of one-electron-oxidized species were performed oxidizing the initial complex by means of AgBF4. A combination of spectroscopic (UV-Vis/NIR- and EPR-) and theoretical (density functional theory (DFT)) studies suggests the formation of a Pt(II)-phenoxyl radical complex. The latter open-shell derivative was structurally characterized by means of X-ray diffraction analysis. Finally, the neutral platinum complex was tested as a mediator in the process of electrocatalytic oxidation of 2-(methylamino)ethanol (MEA). Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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15 pages, 3167 KiB  
Article
Morpholine Radical in the Electrochemical Reaction with Quinoline N-Oxide
by Egor L. Dolengovski, Tatyana V. Gryaznova, Oleg G. Sinyashin, Elena L. Gavrilova, Kirill V. Kholin and Yulia H. Budnikova
Catalysts 2023, 13(9), 1279; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13091279 - 05 Sep 2023
Cited by 1 | Viewed by 978
Abstract
An electrochemical reaction between quinoline N-oxides and morpholine was developed by using Cu(OAc)2 as a catalyst, generating products of 4-aminoquinoline N-oxides in CH2Cl2 or 2-aminoquinoline N-oxides in CH3CN in good yields. With an increase [...] Read more.
An electrochemical reaction between quinoline N-oxides and morpholine was developed by using Cu(OAc)2 as a catalyst, generating products of 4-aminoquinoline N-oxides in CH2Cl2 or 2-aminoquinoline N-oxides in CH3CN in good yields. With an increase in the amount of electricity passed, the product deoxygenates with the formation of aminoquinolines. The advantages of the reaction are mild conditions, room temperature, the use of morpholine rather than its derivatives, and the ability to control the process when the electrolysis conditions change. Bisubstituted quinoline has also been obtained. The redox properties of both individual participants of C–H/N–H cross-coupling and multicomponent systems were established by voltammetry and EPR methods. For the first time, the EPR spectrum of the morpholine radical was recorded at room temperature, and its magnetic resonance parameters were determined in CH2Cl2. Mechanisms for the catalytic reaction have been proposed. This is a simple and easy-to-perform method for introducing a morpholine substituent, important in medicinal chemistry and other fields, by C–H/N–H cross-coupling. Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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16 pages, 6000 KiB  
Article
Insights into the Reactivity of Gd2−xSrxFe2O7 (x = 0 ÷ 0.4) in CO Radical Hydrogenation
by Tatiana F. Sheshko, Elizaveta M. Borodina, Liliya V. Yafarova, Ekaterina B. Markova, Tatiana A. Kryuchkova, Alexander G. Cherednichenko, Irina A. Zvereva and Alexander O. Terent’ev
Catalysts 2023, 13(9), 1256; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13091256 - 30 Aug 2023
Viewed by 781
Abstract
The effect of strontium substitution in the structure of the complex oxide Gd2SrFe2O7 on the production of light olefins by CO hydrogenation was investigated. Perovskite-type oxides Gd2−xSr1+xFe2O7 (x = 0; 0.1; [...] Read more.
The effect of strontium substitution in the structure of the complex oxide Gd2SrFe2O7 on the production of light olefins by CO hydrogenation was investigated. Perovskite-type oxides Gd2−xSr1+xFe2O7 (x = 0; 0.1; 0.2; 0.3; 0.4) were synthesized by sol–gel technology and characterized by XRD, Mössbauer spectroscopy, BET specific area, acidity testing, and SEM. The experimental data revealed a correlation between the state of iron atoms, acidity, and catalytic performance. It was found that with an increase in the content of Sr2+ in the perovskite phase, the basicity of the surface and the oxygen diffusion rate increased. This contributed to the CO dissociative adsorption, formation of active carbon, and its further interaction with atomic hydrogen. Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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16 pages, 6449 KiB  
Article
Effects of Difluorophenyl Substituents on Structural, Redox, and Magnetic Properties of Blatter Radicals
by Dmitry Gulyaev, Andrey Serykh, Evgeny Tretyakov, Anna Akyeva, Mikhail Syroeshkin, Dmitry E. Gorbunov, Svetlana V. Maltseva, Nina P. Gritsan, Galina Romanenko and Artem Bogomyakov
Catalysts 2023, 13(8), 1206; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13081206 - 12 Aug 2023
Cited by 2 | Viewed by 1189
Abstract
Blatter radicals 1-(3,4-difluorophenyl)-(1a) and 1-(2,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1b) were prepared in good yields through oxidation of the corresponding amidrazones using MnO2 in dry CH2Cl2. Cyclic voltammetry showed that both radicals are oxidized and reduced [...] Read more.
Blatter radicals 1-(3,4-difluorophenyl)-(1a) and 1-(2,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1b) were prepared in good yields through oxidation of the corresponding amidrazones using MnO2 in dry CH2Cl2. Cyclic voltammetry showed that both radicals are oxidized and reduced chemically and electrochemically reversibly in accordance with −1/0 and 0/+1 processes. EPR spectroscopy indicated that spin density is mainly delocalized on the triazinyl moiety of the heterocycle. The structure of all paramagnets was unambiguously confirmed by single-crystal X-ray diffraction, and two different 1D chains of alternating radicals were identified. 3,4-difluorophenyl-derivatives 1a are packed into columns composed of two kinds of alternating centrosymmetric dimers, having comparatively short intermolecular distances. In crystals of 2,4-difluorophenyl-derivative 1b, the parallel arrangement of bicyclic moieties and phenyl rings favors the formation of 1D regular chains wherein the radicals are related by translation parallel to the crystallographic stacking axis. Magnetic susceptibility measurements in the 2–300 K region showed that in crystals of the radicals, strong antiferromagnetic interactions are dominant. Subsequent fitting of the dependence of χT on T with 12-membered looped stacks gave the following best-fit parameters: for 1a, g = 2.01 ± 0.05, J1/kB = −292 ± 10 K (according to BS-DFT calculations J2 = 0.12 × J1 and J3 = 0.61 × J1); for 1b, g = 2.04 ± 0.01 J1/kB = −222 ± 17 K. For comparison, in a nonfluorinated related radical, there are only very weak intermolecular interactions along the columns (J/kB = −2.2 ± 0.2 K). These results illustrate the magnitude of the influence of the difluorophenyl substituents introduced into Blatter radicals on their structure and magnetic properties. Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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12 pages, 3164 KiB  
Communication
Copper-Catalyzed Reaction of N-Monosubstituted Hydrazones with CBr4: Unexpected Fragmentation and Mechanistic Study
by Valentine G. Nenajdenko, Anna A. Kazakova, Alexander S. Novikov, Namig G. Shikhaliyev, Abel M. Maharramov, Ayten M. Qajar, Gulnar T. Atakishiyeva, Aytan A. Niyazova, Victor N. Khrustalev, Alexey V. Shastin and Alexander G. Tskhovrebov
Catalysts 2023, 13(8), 1194; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13081194 - 09 Aug 2023
Viewed by 863
Abstract
The copper catalyzed reaction of N-monosubstituted hydrazones with carbon tetrabromide leads to formation of expected dibromodiazadienes and unexpected dibromostyrenes. The experimental and theoretical study of the reaction revealed a key role of N-centered radicals, which can eliminate aryl radicals to form the [...] Read more.
The copper catalyzed reaction of N-monosubstituted hydrazones with carbon tetrabromide leads to formation of expected dibromodiazadienes and unexpected dibromostyrenes. The experimental and theoretical study of the reaction revealed a key role of N-centered radicals, which can eliminate aryl radicals to form the corresponding dibromostyrenes. Alternatively, the oxidation of intermediate N-centered radicals by Cu(II) results in the corresponding diazadienes. These two reaction pathways are competitive directions of the reaction. Consequently, the reaction can be useful for the synthesis of both dibromostyrenes and rare dibromodiazadienes. Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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13 pages, 1348 KiB  
Article
Atom Transfer Radical Addition via Dual Photoredox/Manganese Catalytic System
by Vladislav S. Kostromitin, Vitalij V. Levin and Alexander D. Dilman
Catalysts 2023, 13(7), 1126; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13071126 - 19 Jul 2023
Viewed by 1482
Abstract
Atom transfer radical addition of bromonitromethane and 1,2-dibromotetrafluoroethane to alkenes is described. The reaction is performed under blue light irradiation using two catalysts: 4CzIPN and manganese (II) bromide. The cyanoarene photocatalyst serves for the redox activation of starting organic bromide, while the manganese [...] Read more.
Atom transfer radical addition of bromonitromethane and 1,2-dibromotetrafluoroethane to alkenes is described. The reaction is performed under blue light irradiation using two catalysts: 4CzIPN and manganese (II) bromide. The cyanoarene photocatalyst serves for the redox activation of starting organic bromide, while the manganese salt facilitates the trapping of the alkyl radical with the formation of the carbon–bromine bond. Full article
(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)
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