High performance NMR in ionic liquids

Abstract

Nuclear magnetic resonance techniques for investigations of and in neat ionic liquids have been developed. After thorough optimisation, a resolution comparable to classical solvents is achieved. The technique is usable for a wide range of ILs. Observed nuclei are 1 H and 13 C and potentially 2 H and 19 F. Measurements of T 1 values show multipulse experiments to be feasible.{ This work was presented at the Green Solvents for Synthesis Meeting, held in Bruchsal, Germany, 3-6 October 2004. { Electronic supplementary information (ESI) available: 13 C spectrum of ethanol in [bmim][Tf 2 N] and gradient-selected spectra of ILs. See

14N NMR and Two‐Dimensional Suspension 1H and 13C HRMAS NMR Spectroscopy of Ionic Liquids Immobilized on Silica

“…Thus, the 14 N nucleus could become as important for ionic liquid systems in catalysis as the 31 P nucleus is for homogeneous and immobilized catalysts with phosphine ligands. [3,4] In the following, we will demonstrate with the popular imidazolium-based species [1,2,25] that 14 N NMR spectroscopy can be used to characterize neat and dissolved ionic liquids and that one-and two-dimensional suspension 1 H and 13 C HRMAS NMR spectroscopy can successfully be used to investigate immobilized ionic liquids. 14 N NMR spectroscopy is comparatively easy to accomplish.…”

“…Therefore, it will be especially important to have a probe close to the metal center. This probe could be a 14 N nucleus, which would allow an insight into the catalytic systems to be gained through both its chemical shift and linewidth without the trouble of having to analyze a "crowded" 1 H NMR spectrum of a complex mixture. Thus, the 14 N nucleus could become as important for ionic liquid systems in catalysis as the 31 P nucleus is for homogeneous and immobilized catalysts with phosphine ligands.…”

“…14 N NMR spectroscopy · HRMAS spectroscopy · immobilization · ionic liquids · suspension NMR spectroscopy Abstract: A variety of popular ionic liquids have been synthesized and characterized, including by optimized 14 N NMR spectroscopy of the neat and dissolved ionic liquids. Ionic liquids incorporating Si(OEt) 3 groups have been immobilized on silica in a well-defined manner with the imidazolium moiety remaining intact.…”

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

“…[28] However, ILs of sufficiently low viscosity can also be studied in undiluted pure form by NMR spectroscopy, thus ruling out additional solvent interactions that may complicate the interpretation of the obtained spectra. [31] Finally, apart from coulombic and hydrogen-bonding interactions, dispersion and induction forces also significantly contribute to the specific interactions between anion and cation. [5] From ab inito calculations, considerable differences between ILs and classical molten salts were found due to different dispersive and inductive contributions, which may be an explanation for the reduced melting points and viscosities of ILs.…”

Ionic liquids in sample preparation

“…Thus, ILs are termed "designable solvents" [8], and various applications have reported for them. In analytical chemistry, ILs were used as stationary phases in gas chromatography [9][10][11], additives for capillary electrophoresis [12][13][14][15], matrices for MALDI [16][17][18], as well as solvents for spectral analysis [19][20][21] and electrochemistry [22]. Several reviews that focus on these topics have been published recently [23][24][25][26][27].…”