An Analysis of Radical Diffusion in Ionic Liquids in Terms of Free Volume Theory

Merunka, Dalibor; Perić, Mirosla (2020) An Analysis of Radical Diffusion in Ionic Liquids in Terms of Free Volume Theory. The Journal of chemical physics, 152 . ISSN 0021-9606

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Abstract

The Heisenberg spin exchange – dipole-dipole (HSE-DD) separation method was used to measure the translational diffusion coefficients of the 14N-labeled perdeuterated 2, 2, 6, 6-tetramethyl-4-oxopiperidine-1-oxyl (14N-pDTEMPONE) nitroxide spin probe as a function of temperature in two methylimidazolium ionic liquid series, one based on the tetrafluoroborate (BF4) anion and another one on the bis(trifluoromethane)sulfonimide (TFSI, Tf2N) anion. The obtained translational diffusion coefficients of 14N-pDTEMPONE were analyzed in terms of the Cohen–Turnbull free volume theory. It was found that the Cohen-Turnbull theory describes, exceptionally well, the translational diffusion of 14N-pDTEMPONE in all the ionic liquids in the measured temperature range. Also, the Cohen-Turnbull theory was applied to the viscosity and self-diffusion coefficients of the cation and anion - taken from literature - in the same ionic liquids. The critical free volume for the self-diffusion of the cation and anion in a given ionic liquid is the same, which suggests that the diffusion of each ionic pair is coordinated. The critical free volumes for the 14N-pDTEMPONE diffusion, self-diffusion, and viscosity for a given cation were about twenty percent greater in the TFSI based ionic liquids than in the BF4 based ionic liquids. It appears that the ratio of the critical free volumes for a given cation between the two series correlates with the ratio of their densities.

Item Type:	Article
Additional Information:	This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 152, 024502 (2020) and may be found at https://aip.scitation.org/doi/10.1063/1.5138130.
Uncontrolled Keywords:	electron paramagnetic resonance ; ionic liquids ; diffusion
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 Studija važnosti spinskih međudjelovanja kao osnova za nove pristupe u istraživanju materijala-SPES Marina Ilakovac-Kveder IP-2018-01-3168 HRZZ
Depositing User:	Dalibor Merunka
Date Deposited:	11 Mar 2021 12:45
URI:	http://fulir.irb.hr/id/eprint/6339
DOI:	10.1063/1.5138130

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