TY - JOUR

T1 - (Pyrrole-2,5-diyl)-bis(nitronyl nitroxide) and-bis(iminonitroxide)

T2 - Specific features of the synthesis, structure, and magnetic properties

AU - Tretyakov, Evgeny

AU - Tkacheva, Anastasia

AU - Romanenko, Galina

AU - Bogomyakov, Artem

AU - Stass, Dmitri

AU - Maryasov, Alexander

AU - Zueva, Ekaterina

AU - Trofimov, Boris

AU - Ovcharenko, Victor

PY - 2020/3/26

Y1 - 2020/3/26

N2 - 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 = −2JS1·S2).

AB - 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 = −2JS1·S2).

KW - Diradicals

KW - Iminonitroxides

KW - Magnetochemistry

KW - Nitronyl nitroxides

KW - Pyrrole derivatives

KW - Quantum-chemical calculations

KW - diradicals

KW - nitronyl nitroxides

KW - magnetochemistry

KW - NITRONYL-NITROXIDE

KW - STATE

KW - DISJOINT

KW - DIMERS

KW - THIOPHENE

KW - quantum-chemical calculations

KW - DIRADICALS

KW - pyrrole derivatives

KW - iminonitroxides

UR - http://www.scopus.com/inward/record.url?scp=85082593531&partnerID=8YFLogxK

U2 - 10.3390/molecules25071503

DO - 10.3390/molecules25071503

M3 - Article

C2 - 32224961

AN - SCOPUS:85082593531

VL - 25

JO - Molecules

JF - Molecules

SN - 1420-3049

IS - 7

M1 - 1503

ER -