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An air-stable, neutral phenothiazinyl radical with substantial radical stabilization energy

The vital effect of radical states on the pharmacological activity of phenothiazine-based drugs has long been speculated. Whereas cationic radicals of N-substituted phenothiazines show high stability, the respective neutral radicals of N-unsubstituted phenothiazines have never been isolated. Herein,...

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Bibliographic Details
Main Authors: Sigmund, Lukas M. (Author) , Ebner, Fabian (Author) , Jöst, Christoph (Author) , Spengler, Jonas (Author) , Gönnheimer, Nils (Author) , Hartmann, Deborah (Author) , Greb, Lutz (Author)
Format: Article (Journal)
Language:English
Published: 2020
In: Chemistry - a European journal
Year: 2020, Volume: 26, Issue: 14, Pages: 3152-3156
ISSN:1521-3765
DOI:10.1002/chem.201905238
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1002/chem.201905238
Verlag, kostenfrei, Volltext: https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201905238
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Author Notes:Lukas M. Sigmund, Fabian Ebner, Christoph Jöst, Jonas Spengler, Nils Gönnheimer, Deborah Hartmann, and Lutz Greb
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Summary:The vital effect of radical states on the pharmacological activity of phenothiazine-based drugs has long been speculated. Whereas cationic radicals of N-substituted phenothiazines show high stability, the respective neutral radicals of N-unsubstituted phenothiazines have never been isolated. Herein, the 1,9-diamino-3,7-di-tert-butyl-N1,N9-bis(2,6-diisopropylphenyl)-10H-phenothiazin-10-yl radical (SQH2.) is described as the first air-stable, neutral phenothiazinyl free radical. The crystalline dark-blue species is characterized by means of EPR and UV/Vis/near-IR spectroscopy, as well as cyclic voltammetry, spectro-electrochemical analysis, single-crystal XRD, and computational studies. The SQH2. radical stands out from other aminyl radicals by an impressive radical stabilization energy and its parent amine has one of the weakest N−H bond dissociation energies ever determined. In addition to serving as open-shell reference in medicinal chemistry, its tridentate binding pocket or hydrogen-bond-donor ability might enable manifold uses as a redox-active ligand or proton-coupled electron-transfer reagent.
Item Description:First published: 16 January 2020
Gesehen am 22.11.2021
Physical Description:Online Resource
ISSN:1521-3765
DOI:10.1002/chem.201905238

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