Issue 26, 2016

Bulk nanostructure of the prototypical ‘good’ and ‘poor’ solvate ionic liquids [Li(G4)][TFSI] and [Li(G4)][NO3]

Abstract

The bulk nanostructures of a prototypical ‘good’ solvate ionic liquid (SIL) and ‘poor’ SIL have been examined using neutron diffraction and empirical potential structure refinement (EPSR) simulated fits. The good SIL formed by a 1 : 1 mixture of lithium bis(trifluoromethylsulfonyl)imide (Li[TFSI]) in tetraglyme (G4), denoted [Li(G4)][TFSI], and the poor SIL formed from a 1 : 1 mixture of lithium nitrate (Li[NO3]) in G4, denoted [Li(G4)][NO3], have been studied. In both SILs there are strong Lewis acid–base interactions between Li+ and ligating O atoms. However, the O atoms coordinated to Li+ depend strongly on the counter anion present. Li⋯O coordination numbers with G4 are 2–3 times higher for [Li(G4)][TFSI] than [Li(G4)][NO3], and conversely the Li⋯O anion coordination number is 2–3 times higher in [Li(G4)][NO3]. In both solvates the local packing of Li around G4 O atoms are identical but these interactions are less frequent in [Li(G4)][NO3]. In both SILs, Li+ has a distribution of coordination numbers and a wide variety of different complex structures are present. For [Li(G4)][NO3], there is a significant proportion uncoordinated G4 in the bulk; ∼37% of glyme molecules have no Li⋯O contacts and each G4 molecule coordinates to an average of 0.5 Li+ cations. Conversely, in [Li(G4)][TFSI] only ∼5% of G4 molecules lack Li⋯O contacts and G4 molecules coordinates to an average of 1.3 Li+ cations. Li+ and G4 form polynuclear complexes, of the form [Lix(G4)y]x+, in both solvates. For [Li(G4)][TFSI] ∼35% of Li+ and G4 form 1 polynuclear complexes, while only ∼10% of Li+ and G4 form polynuclear complexes in [Li(G4)][NO3].

Graphical abstract: Bulk nanostructure of the prototypical ‘good’ and ‘poor’ solvate ionic liquids [Li(G4)][TFSI] and [Li(G4)][NO3]

Supplementary files

Article information

Article type
Paper
Submitted
10 Jan 2016
Accepted
27 Jan 2016
First published
28 Jan 2016
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2016,18, 17224-17236

Bulk nanostructure of the prototypical ‘good’ and ‘poor’ solvate ionic liquids [Li(G4)][TFSI] and [Li(G4)][NO3]

T. Murphy, S. K. Callear, N. Yepuri, K. Shimizu, M. Watanabe, J. N. Canongia Lopes, T. Darwish, G. G. Warr and R. Atkin, Phys. Chem. Chem. Phys., 2016, 18, 17224 DOI: 10.1039/C6CP00176A

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