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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

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N. N. Vorozhtsov Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, 9 Ac. Lavrentiev Avenue, 630090 Novosibirsk, Russia
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International Tomography Center, Siberian Branch of Russian Academy of Sciences, 3a Institutskaya Str., 630090 Novosibirsk, Russia
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V. V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, 3 Institutskaya Str., 630090 Novosibirsk, Russia
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Novosibirsk State University, 2 Pirogova Str., 630090 Novosibirsk, Russia
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Kazan National Research Technological University, 68 Karl Marx Str., 420015 Kazan, Russia
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Kazan Federal University, 18 Kremlyovskaya Str., 420008 Kazan, Russia
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A. E. Favorsky Institute of Chemistry, Siberian Branch of Russian Academy of Sciences, 1 Favorsky Str., Irkutsk 664033, Russia
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Authors to whom correspondence should be addressed.
Molecules 2020, 25(7), 1503; https://doi.org/10.3390/molecules25071503 (registering DOI)
Received: 28 February 2020 / Revised: 21 March 2020 / Accepted: 25 March 2020 / Published: 26 March 2020
(This article belongs to the Special Issue Stable Organic Radicals)
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…HN, 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).
Keywords: nitronyl nitroxides; iminonitroxides; diradicals; pyrrole derivatives; magnetochemistry; quantum-chemical calculations nitronyl nitroxides; iminonitroxides; diradicals; pyrrole derivatives; magnetochemistry; quantum-chemical calculations
MDPI and ACS Style

Tretyakov, E.; Tkacheva, A.; Romanenko, G.; Bogomyakov, A.; Stass, D.; Maryasov, A.; Zueva, E.; Trofimov, B.; Ovcharenko, V. (Pyrrole-2,5-Diyl)-Bis(Nitronyl Nitroxide) and-Bis(Iminonitroxide): Specific Features of the Synthesis, Structure, and Magnetic Properties. Molecules 2020, 25, 1503.

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