Structure and dynamics of 1-n -alkyl-3- n -methylimidazolium tetrafluoroborate + acetonitrile mixtures

Stoppa, A., Hunger, J., Hefter, G. and Buchner, R. (2012) Structure and dynamics of 1-n -alkyl-3- n -methylimidazolium tetrafluoroborate + acetonitrile mixtures. The Journal of Physical Chemistry B, 116 (25). pp. 7509-7521.

Abstract

A detailed investigation of the binary mixtures of the ionic liquids (ILs) 1-N-R-3-N-methylimidazolium tetrafluoroborate (R = ethyl, n-butyl, n-hexyl) with the important molecular solvent acetonitrile (AN) over the entire composition range has been made at 25 °C using broadband dielectric spectroscopy. All spectra showed two modes: a Cole–Cole (CC) mode centered at 2 GHz and a Debye mode centered at 50 GHz. However, detailed analysis indicated both relaxations were composites. The Debye mode arises from the rotational diffusion of free AN molecules with contributions from ultrafast vibrations and librations of the ILs. The CC mode corresponds to the jump rotation of the imidazolium cations and the hindered rotational diffusion of “slow” AN molecules solvating them. At very low IL concentrations 1:1 contact ion pairs are dominant. Overall, these IL + AN mixtures can be divided into two broad regions: at IL mole fraction (xIL) 0.2 the IL behaves as a rather weakly associated conventional electrolyte while at xIL 0.2 it takes on its IL characteristics, “lubricated” by the AN.

Publication Type:	Journal Article
Murdoch Affiliation:	School of Chemical and Mathematical Science
Publisher:	American Chemical Society
Copyright:	© ACS
URI:	http://researchrepository.murdoch.edu.au/id/eprint/9499

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