Abstract: Three imidazoline-type nitroxide biradicals of the similar composition R (5) (NO) -CH=N-N=CH-R (5) (N) , B1, R (5) (NO) -CH=N-N=C(CH3)-R (5) (N) , B2, and R (5) (N) -C(CH3)=N-N=C(CH3)-R (5) (N) , B3, with R (5) (N) and R (5) (NO) denoting, respectively, the nitroxide rings 1-oxyl-2,2,5,5-tetramethyl-3-imidazoline and 1-oxyl-2,2,5,5-tetramethyl-3-N-oxide imidazoline, have been studied by X-band electron paramagnetic resonance (EPR) spectroscopy. Variations of the intramolecular electron spin exchange in these biradicals dissolved in ethanol and the room temperature ionic liquid bmimBF(4) were characterized as a function of temperature by means of the analysis of the EPR lines shape. Thermodynamic parameters of the conformational rearrangements in ethanol were calculated. Analyzing the EPR spectra of these biradicals in bmimBF(4), it was revealed that the two-conformational model does not describe their conformational transitions. Moreover, the observed EPR spectra are not central symmetric especially at low temperatures that cannot be described and explained in the framework of the current theory of the intramolecular spin exchange. Probable reasons of this "strange" behavior are discussed.

Cite: Kokorin A.I. , Mladenova-Kattnig B.Y. , Grigor'ev I.A. , Grampp G.
Unexpected Features of the Intramolecular Spin Exchange in Imidazoline Nitroxide Biradicals Dissolved in Ionic Liquids
Applied Magnetic Resonance. 2017. V.48. N3. P.287-296. DOI: 10.1007/s00723-016-0858-5 WOS Scopus РИНЦ

Dates:

Published online:	Dec 31, 2016
Published print:	Mar 1, 2017

Identifiers:

Web of science	WOS:000395201000006
Scopus	2-s2.0-85007422231
Elibrary	29469175
OpenAlex	W2563538936

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