Applying neutron diffraction with isotopic substitution to the structure and proton-transport pathways in protic imidazolium bis{(trifluoromethyl)sulfonyl}imide ionic liquids

Abstract

Neutron diffraction with isotopic substitution has been applied to examine the potential for complex-ion formation in protic imidazolium bis{(trifluoromethyl)sulfonyl}imide ionic liquids.

Short-Range Order and Transport Properties in Mixtures of the Protic Ionic Liquid [C2HIm][TFSI] with Water or Imidazole

“…Of particular interest are the cation–cation and anion–anion shortest distances that in the neat ionic liquid are peaked at ∼7.4 Å; see Figure for the specific case of cation–cation correlations. The value of 7.4 Å is fully consistent with that found by a study based on neutron diffraction experiments on the protic ionic liquid imidazolium-TFSI (HIm-TFSI) and its mixtures with imidazole . Upon addition of water (e.g., at χ = 0.5) the maximum of the radial distribution function shifts very slightly to lower distances but does not change in intensity.…”

“…The system investigated also displayed a low ionic aggregation and a high proton transference number. The [Im]:[HTFSI] system, at equimolar and nonstoichiometric compositions, was later studied by applying neutron diffraction with isotopic substitution, revealing, among other local structural features, interesting phase diagrams with clear eutectic points . QENS experiments, which can probe the time domain of picoseconds typical of fast local dynamics, revealed a proton motion faster than the core of the cation also in the protic ionic liquid triethyl­ammonium triflate ([TEA]­[TfO]) .…”

Alkylimidazolium Protic Ionic Liquids: Structural Features and Physicochemical Properties

“…So the decomposition of such ionic pairs requires high energy, i. e. they are characterized by a higher decomposition temperature. [19] The following anion series, in which the T dec values increase, can be constructed from the data in Table 3: HIm 85 [47] 188 [48] 122.9 [49] 193 [50] 193 this work 69 [51] 73 [6,7] 74 [52] 72.76 [53] 131.2 [49] MeHIm 20.88 [54,55] 41.9 this work 47 [47] 117 [5] 60.3 [56] 84 [8] 92 [49] 94.3 [57] 104 [5] 9 [8,10] 12.5 [4] 43 [5] 48.15 [53] 49 [44] 52 [12,51] À 23 [58] 51 [58] 65 [5] 35.8 [49] 36.9 [59] 37 [8,60] 52.4 [61] 60 [62] 69.6 [63] 70 [8] EtHIm 59 [9] À 12.7 [57] 8 [8] 13.4 [64] 17 this work 18 [9] 27 [65] À 12 [4] 2.35 …”

“…28.5 this work 6.1 [67] 7.49 [53] 7.9 this work BuHIm 67 [5] 70 [9] 23 [5] 28 [9] 48 [5] 6* [62] 129 [5] Water content in the PILs synthesized in this work (wt.%): MeHIm/HSO 4 : 0.004 (40 ppm); EtHIm/TfO: 0.002 (20 ppm); PrHIm/HSO 4 : 0.02 (200 ppm); PrHIm/ TfO: 0.04 (400 ppm); PrHIm/TFSI: 0.08 (800 ppm). The values are shown in italics if the original papers contain no information about the water content: [4,6,7,12,47,50,52,56,57,[60][61][62]64,74,76,79] Water content (wt.%): < 0.00001 (< 0.1 ppm); [48,59] < 0.01 (< 100 ppm); [5,9,19,53,65,68,69,75] 0.01; [44] < 0.025 (< 250 ppm); [49,65,77,81] < 0.05 (< 500 ppm); [54,55,58,67,70,78,80,…”

On the hydration of DOPE in solution

“…As a result, Empirical Potential Structure Refinement (EPSR) simulations were employed, where this Monte Carlo-based simulation technique has been specifically designed to generate a computational model of a disordered system which fits a set of measured diffraction data in order to extract a full set of correlations for any given system. 19,20 This analysis method has been used to explore a range of chemical and biological solutions, [21][22][23][24][25][26][27][28][29][30] as well as specifically for the hydration of lipid molecules. 10,[12][13][14]31 Here EPSR simulations were performed on a box containing 10 DOPE, 50 H 2 O and 3000 CHCl 3 molecules at the temperature and atomic number density of the measurement (298 K and 0.0374 atoms/Å 3 ).…”