Determination of inter‐ionic and intra‐ionic interactions in a monofluorinated imidazolium ionic liquid by a combination of X‐ray crystallography and NOE NMR spectroscopy

Abstract

We report the very first application of a Transient 1D H{ F} NOE NMR experiment in neat ionic liquids. In comparison with classical 2D HOESY NMR spectroscopy, a substantial reduction in measurement time is gained with comparable quality and information content of the spectra. In combination with classical X-ray crystallography, we have applied this technique for the determination of inter-ionic distances (i.e. probabilities of presence) utilizing an ionic liquid containing a monofluorinated imidazolium cation. Copyright © 2017 John Wiley & Sons, Ltd.

Lithium Salt Effects on the Liquid Structure of Choline Chloride–Urea Deep Eutectic Solvent

“…The interaction of lithium with urea and cholinium protons (Figure 2b), which is observed experimentally, is indirect, through the chloride anion (Figure 3a−d), as these species are found in the second coordination shell of lithium at a characteristic distance of 5.05 Å. Although the intensity of this peak for the cholinium head group is greater than for urea, we 7 Li NOE build-up curves fitted using eq S5, 19,20 should be aware of a twice smaller number of cholinium ions that are taken into account when normalizing the RDFs. Indeed, urea dominates in the second coordination shell with 6.75 molecules (up to r min = 7.32 Å), while only 5.6 cholinium cations are found around lithium (up to r min = 7.72 Å).…”

“…Proton–lithium heteronuclear Overhauser effect spectroscopy ( 1 H– 7 Li HOESY) was used to gain insights into short-range correlations around lithium cations (Figure S1), assuming that the upper limit for detecting 1 H– 7 Li contacts is ca 5 Å. Indeed, the markedly different 1 H and 7 Li gyromagnetic ratios allow us to overcome the long-ranged nature of the intermolecular NOE, thus truly reflecting the short-range connectivities around Li + . − Normalized NOE build-up curves obtained at 298 K at variable mixing times (50 ms–3 s) were fitted using a modified version of the Solomon equation for a dipolar-coupled heteronuclear system, , with the relative cross-relaxation σ IS as the only parameter (Figures and SI for a theoretical description). The closest proximity is between Li + and urea NH 2 protons, but a consistent cross-relaxation is also observed with the N -trimethylammonium head of Ch.…”

“…Figure 1. Normalized 1 H−7 Li NOE build-up curves fitted using eq S5,19,20 and corresponding relative cross-relaxation rates normalized to the highest value.…”

Lithium Speciation in the LiPF6/PC Electrolyte Studied by Two-Dimensional Heteronuclear Overhauser Enhancement and Pulse-Field Gradient Diffusometry NMR

“…Theoretical descriptions − of intermolecular nOe have shown that the spectral density function is no longer Lorentzian and the deduction of intermolecular distance information from the observed cross-relaxation rate is rendered difficult owing to the characteristic r – n dependence, n varying between 1 and 6 depending on the NMR frequency of the nuclei and their dynamics. Further interpretation of the cross-relaxation rates in terms of internuclear distances would be aided by molecular dynamics simulations and adaptation of motional models which provide a comprehensive description of the complex rotational and translational dynamics in the LIB electrolyte. ,, …”

PROSPECTS FOR THE CHEMISTRY OF IMIDAZOLE DERIVATIVES (Review)

“…The fluorine derivative was treated with hexamethyldisilazide(HMDS) /reflux for 10 h to yield the desired N-TMS derivative (90-95%) as an intermediate product for glycosylation. Lingsheid Y., Paul M., Breohl A., Giernoth R. proposed a scheme for obtaining the fluoroimidazole analogues [46]. 1-Butyl-4-fluoro-1H-imidazole (58)was obtained by deprotonation, using sodium hydride in N,Ndimethylformamide, followed by alkylation with 1-iodobutane.…”