Peculiarities of Spin Exchange in Nitroxide Biradicals Containing Two para-Phenylene Groups in the Bridge: EPR Investigation and DFT Calculations
- Authors: Kokorin A.I.1, Gromov O.I.1,2, Kálai T.3, Hideg K.3
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Affiliations:
- N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences
- Chemistry Department, M. Lomonosov Moscow State University
- Institute of Organic and Medical Chemistry, University of Pécs
- Issue: Vol 47, No 11 (2016)
- Pages: 1283-1293
- Section: Original Paper
- URL: https://journals.rcsi.science/0937-9347/article/view/247571
- DOI: https://doi.org/10.1007/s00723-016-0826-0
- ID: 247571
Cite item
Abstract
Two nitroxide biradicals of similar composition: R5-C≡C-Ph-Ph-C≡C-R5 (B3a) and R6-C≡C-Ph-Ph-C≡C-R6 (B3b), where Ph = p-C6H4, and R6 is 2,6,6-tetramethyl-5,6-dihydropyridin-1(2H)-yloxyl, and R5 is 2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yloxyl nitroxide rings, have been studied by electron paramagnetic resonance (EPR) spectroscopy. Variations of the intramolecular electron spin exchange in the biradicals, dissolved in toluene, as a function of temperature were characterized by changes in the isotropic 14N hyperfine splitting (hfs) constant a, values of the exchange integral |J|, and compared with the data obtained by density functional theory calculations (DFT). Thermodynamic parameters of the conformational rearrangements were calculated. Geometries of nitroxide biradicals in PES local minima and transition states in the triplet state were calculated at UDFT/B3LYP level with split-valence basis set cc-PVTZ. Probable differences in biradicals behavior are discussed.
About the authors
Alexander I. Kokorin
N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences
Author for correspondence.
Email: alex-kokorin@yandex.ru
Russian Federation, Moscow
Oleg I. Gromov
N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences; Chemistry Department, M. Lomonosov Moscow State University
Email: alex-kokorin@yandex.ru
Russian Federation, Moscow; Moscow
Tamás Kálai
Institute of Organic and Medical Chemistry, University of Pécs
Email: alex-kokorin@yandex.ru
Hungary, Pécs
Kálmán Hideg
Institute of Organic and Medical Chemistry, University of Pécs
Email: alex-kokorin@yandex.ru
Hungary, Pécs