Pyrrolidinium-based ionic liquids doped with lithium salts: How does Li

Franca Castiglione, Antonino Famulari, Guido Raos, Stefano V. Meille, Andrea Mele, Giovanni Battista Appetecchi, Stefano Passerini

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Abstract

We present the characterization of LiX-doped room-temperature ionic liquids (ILs) based on the N-butyl-N-methyl pyrrolidinium (PYR14) cation with two fluorinated anions: (trifluoromethanesulfonyl)-(nonafluorobutanesulfonyl)imide (X=IM14) and bis(pentafluoroethanesulfonyl)imide (X=BETI). The new data are also compared with previous results on PYR14TFSI (bis(trifluoromethanesulfonyl)imide). Their local organization has been investigated via NMR nuclear Overhauser effect (NOE) experiments for {1H-19F} and {1H-7Li} that give us details on PYR14+/X-and PYR14+/Li+contacts. We confirm the presence of [Li(X)2]-coordinated species in all systems. The long-range, intermolecular NOEs have been detected and provide information on the ions organization beyond the first solvation sphere. The ionic conductivity, viscosity and self-diffusion coefficients of the ionic mixtures have also been measured. The activation energies for the diffusion of the individual ions and for the fluidity are compared with those for the pure ILs. Finally, density functional calculations on [Li(BETI)2]-, [Li(IM14)2]-, and [Li(TFSI)2]-complexes demonstrate that the minimum energy structures for all systems correspond to a tetrahedral coordination of the Li-ion by four oxygen atoms of the anions. Assuming very simple key steps for the Li+diffusion process (i.e., the concerted breaking and formation of Li-O bonds or the rearrangement around a tetrahedrally coordinated Li+), we calculate activation barriers that agree well with the experimental results (approximately 46 kJ/mol, in all systems).
Original languageEnglish
Pages (from-to)13679 - 13688
Number of pages10
JournalJournal of Physical Chemistry B
Volume118
Issue number47
DOIs
Publication statusPublished - 26 Nov 2014
Externally publishedYes

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All Science Journal Classification (ASJC) codes

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

Cite this

Castiglione, F., Famulari, A., Raos, G., Meille, S. V., Mele, A., Appetecchi, G. B., & Passerini, S. (2014). Pyrrolidinium-based ionic liquids doped with lithium salts: How does Li. Journal of Physical Chemistry B, 118(47), 13679 - 13688. https://doi.org/10.1021/jp509387r