Radical Diffusion in Viscous Liquids by Electron Paramagnetic Resonance

Merunka, Dalibor; Perić, Miroslav (2019) Radical Diffusion in Viscous Liquids by Electron Paramagnetic Resonance. Journal of molecular liquids, 277 . pp. 886-894. ISSN 0167-7322

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Abstract

Relative diffusion of free radicals in solution modulates the Heisenberg spin exchange and dipole-dipole interactions among them, which affects their electron paramagnetic resonance (EPR) spectra. The radical concentration dependence of EPR parameters can, in turn, give information about radical diffusivity in a liquid. We studied the diffusivities of the 14N- and 15N-labeled perdeuterated TEMPONE radicals at various temperatures in three viscous liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid, propylene carbonate, and ethylene glycol. By fitting EPR spectra at various radical concentrations, we obtained the concentration coefficients of EPR parameters. The concentration coefficients were related to the radical diffusivity by solving the kinetic equations for the spin evolution of a radical pair, considering the radicals as continuously diffusing spherical objects in the hard-core pair potential. We tested the method by comparing the calculated radical diffusivities of isotopically substituted TEMPONE radicals. Temperature dependences of radical diffusivities were discussed in terms of the Stokes-Einstein relation. Additionally, the radical diffusivities were compared to the self-diffusivities of the studied liquids. At lower temperatures, the radical diffusivities follow the self-diffusivities, while at the higher temperatures, the radical diffusivities start deviating from the self-diffusivities.

Item Type:	Article
Uncontrolled Keywords:	molecular liquids ; ionic liquids ; electron paramagnetic resonance ; nitroxide radicals ; spin interactions ; tracer diffusivity
Subjects:	NATURAL SCIENCES > Physics > Condensed Matter Physics NATURAL SCIENCES > Chemistry > Physical Chemistry
Divisions:	Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Karakterizacija niskotemperaturne molekulske dinamike sustava s neuređenom rešetkom metodom ESR Ilakovac Kveder, Marina IP-2013-11-1108 HRZZ Studija važnosti spinskih međudjelovanja kao osnova za nove pristupe u istraživanju materijala Ilakovac Kveder, Marina IP-2018-01-3168 HRZZ
Depositing User:	Dalibor Merunka
Date Deposited:	14 Dec 2020 11:53
URI:	http://fulir.irb.hr/id/eprint/6134
DOI:	10.1016/j.molliq.2019.01.006

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