Rotational Dynamics of Nitroxide Biradical in Room-Temperature Ionic Liquids Measured by Quantitative Simulation of EPR Spectra

A. V. Bogdanov*, B. Y. Mladenova Kattnig, A. Kh Vorobiev, G. Grampp, A. I. Kokorin

*Corresponding author for this work

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Temperature dependences of electron paramagnetic resonance (EPR) spectra of an imidazoline nitroxide biradical spin probe in a series of room-temperature ionic liquids in the temperature range 124-390 K have been quantitatively simulated. The unusual asymmetric EPR spectrum shape previously observed in these systems [Kokorin et al., Appl. Magn. Res. 48 (2016) 287] is shown to originate from anisotropic rotational diffusion of the probe molecule. All experimental spectra were quantitatively reproduced in simulation using a unified set of geometrical and magnetic parameters of the spin probe, which were found to be fully consistent with the biradical geometry obtained from density functional theory calculations. Temperature dependences of rotation diffusion coefficient of the probe characterize the molecular mobility of the ionic liquid, whereas the temperature dependences of the spin-exchange integral J and of the isotropic hyperfine interaction constant, aN, are shown to reflect the intramolecular conformation motions of the biradical probe.

Original languageEnglish
Pages (from-to)11007-11014
Number of pages8
JournalThe Journal of Physical Chemistry B
Issue number48
Publication statusPublished - 3 Dec 2020

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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