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Special Issue "Stable Organic Radicals"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: 31 December 2020.

Special Issue Editor

Prof. Dr. Evgeny Tretyakov
Website
Guest Editor
N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Interests: organic radicals; diradicals and high spin polyradicals; molecule-based magnets including metal-radical magnets; self-assembly and supramolecular interactions; magneto-structural correlations; magnetic sensors and probes; applications in chemistry, biology, and medicine

Special Issue Information

Dear Colleagues,

The versatility and wide potential of stable organic radicals have continued to allow the discovery of unique and sometimes unexpected properties and functions that are being utilized in functional devices. Cutting-edge research in the field of chemistry and the application of stable radicals have been performed based on clearly defined strategic objectives as well as an emergent approach that comes from unpredicted discoveries. Only a decade or so has passed since stable high-spin molecules with parallel spin alignment (triplet diradicals) were developed. Also recently, there have been widespread efforts aimed at developing new materials with technologically relevant properties (magnetism, conductivity, recharging battaries) for which stable radicals are excellent functioanal blocks due to the presence of unpaired electrons. Polymer chemistry received a significant boost after the development of stable-radical-mediated living radical polymerization processes. Nowadays, stable radicals play an important role as spin probes for the investigation and real-time monitoring of microstructure and membrane dynamics, metabolism and oxygenation, and the pH and redox status in cellular systems for studying the dynamics in biological systems.

This Special Issue aims to attract contributions on all aspects of the chemistry and application of stable organic radicals to stimulate inter-science exchange with ideas and opinions, providing mutual benefits and further progress in the synthesis, study, and new applications of stable organic radicals and their derivatives.

Prof. Dr. Evgeny Tretyakov
Guest Editor

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 papers will be 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. Molecules is an international peer-reviewed open access semimonthly 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 2000 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

  • organic radicals
  • diradicals and high spin polyradicals
  • molecule-based magnets including metal-radical magnets
  • self-assembly and supramolecular interactions
  • magneto-structural correlations
  • magnetic sensors and probes
  • applications in chemistry, biology, and medicine

Published Papers (3 papers)

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Research

Open AccessArticle
Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates
Molecules 2020, 25(10), 2430; https://doi.org/10.3390/molecules25102430 (registering DOI) - 22 May 2020
Abstract
Organophosphorus compounds occupy a significant position among the plethora of organic compounds, but a limited number of paramagnetic phosphorus compounds have been reported, including paramagnetic phosphonates. This paper describes the syntheses and further transformations of pyrroline and piperidine nitroxide phosphonates by well-established methods, [...] Read more.
Organophosphorus compounds occupy a significant position among the plethora of organic compounds, but a limited number of paramagnetic phosphorus compounds have been reported, including paramagnetic phosphonates. This paper describes the syntheses and further transformations of pyrroline and piperidine nitroxide phosphonates by well-established methods, such as the Pudovik, Arbuzov and Horner-Wadsworth-Emmons (HWE) reactions. The reaction of paramagnetic α-bromoketone produced a vinylphosphonate in the Perkow reaction. Paramagnetic α-hydroxyphosphonates could be subjected to oxidation, elimination and substitution reactions to produce various paramagnetic phosphonates. The synthesized paramagnetic phosphonates proved to be useful synthetic building blocks for carbon-carbon bond-forming reactions in the Horner-Wadsworth-Emmons olefination reactions. The unsaturated compounds achieved could be transformed into various substituted pyrroline nitroxides, proxyl nitroxides and paramagnetic polyaromatics. The Trolox® equivalent antioxidant capacity (TEAC) of new phosphonates was also screened, and tertiary α-hydroxyphosphonatate nitroxides exhibited remarkable antioxidant activity. Full article
(This article belongs to the Special Issue Stable Organic Radicals)
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Open AccessArticle
(Pyrrole-2,5-Diyl)-Bis(Nitronyl Nitroxide) and-Bis(Iminonitroxide): Specific Features of the Synthesis, Structure, and Magnetic Properties
Molecules 2020, 25(7), 1503; https://doi.org/10.3390/molecules25071503 - 26 Mar 2020
Abstract
In contrast to diradicals connected by alternant hydrocarbons, only a few studies have addressed diradicals connected by nonalternant hydrocarbons and their heteroatom derivatives. Here, the synthesis, structure, and magnetic properties of pyrrole-2,5-diyl–linked bis(nitronyl nitroxide) and bis(iminonitroxide) diradicals are described. The diradicals show characteristic [...] Read more.
In contrast to diradicals connected by alternant hydrocarbons, only a few studies have addressed diradicals connected by nonalternant hydrocarbons and their heteroatom derivatives. Here, the synthesis, structure, and magnetic properties of pyrrole-2,5-diyl–linked bis(nitronyl nitroxide) and bis(iminonitroxide) diradicals are described. The diradicals show characteristic electron spin resonance spectra in dilute glassy solutions, from which conclusions about the presence of distinct conformations, their symmetry, and interspin distance were made. X-ray diffraction analysis of the diradicals revealed that paramagnetic moieties lie in the plane of the pyrrole ring, because of the formation of an intramolecular hydrogen bond, ONO…H−N, with O…H distances of 2.15–2.23 Å. The N–O groups participating in the formation of H-bonds have greater bond lengths (~1.29 Å) as compared with nonparticipating groups (~1.27 Å). The nitronyl nitroxide and iminonitroxide diradicals showed an intramolecular antiferromagnetic interaction, with J = −77.3 and −22.2 cm−1, respectively (H = −2JS1S2). Full article
(This article belongs to the Special Issue Stable Organic Radicals)
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Open AccessArticle
Aromatic SNF-Approach to Fluorinated Phenyl tert-Butyl Nitroxides
Molecules 2019, 24(24), 4493; https://doi.org/10.3390/molecules24244493 - 08 Dec 2019
Abstract
The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-butylamine, followed by the oxidation of thus formed tert-butylanilines (2a,b) with meta-chloroperoxybenzoic acid led to functionalized perfluorinated phenyl tert-butyl nitroxides [...] Read more.
The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-butylamine, followed by the oxidation of thus formed tert-butylanilines (2a,b) with meta-chloroperoxybenzoic acid led to functionalized perfluorinated phenyl tert-butyl nitroxides [namely, 4-(N-tert-butyl(oxyl)amino)heptafluorotoluene (3a) and 4-(N-tert-butyl(oxyl)amino)tetrafluorobenzonitrile (3b)] with nearly quantitative total yields. The molecular and crystal structures of nitroxide 3a were proved by single crystal X-ray diffraction analysis. The radical nature of both nitroxides was confirmed by ESR data. The interaction of Cu(hfac)2 with the obtained nitroxides 3a,b gave corresponding trans-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2O,O′)bis{4-(N-tert-butyl(oxyl)amino)perfluoroarene-κO}copper (II) complexes ([Cu(hfac)2(3a)2] and [Cu(hfac)2(3b)2]). X-ray crystal structure analysis showed square bipyramid coordination of a centrally symmetric Cu polyhedron with the axial positions occupied by oxygen atoms of the nitroxide groups. Magnetic measurements revealed intramolecular ferromagnetic exchange interactions between unpaired electrons of Cu(II) ions and paramagnetic ligands, with exchange interaction parameters JCu–R reaching 53 cm−1. Full article
(This article belongs to the Special Issue Stable Organic Radicals)
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