How to Disentangle Cation and Anion Dynamics of Fully Protonated Ionic Liquids: A Fast Field Cycling NMR Case Study
Year: 2025
Type: article
Abstract: ABSTRACT The molecular dynamics of ionic liquids (ILs) can be probed using fast field cycling (FFC) NMR relaxometry. Conventionally, such studies focus on ILs where only one ionic species carries NMR‐active nuclei or on systems combining H nuclei on the cations with F nuclei on the anions. This way, the dynamics of cations and anions can be resolved individually. However, the situation becomes considerably more complex in fully protonated systems where both ions contain protons, because the various relaxation pathways can no longer be disentangled. Here we report the first FFC NMR investigation of such a case, using the IL triethylammonium methanesulfonate ([TEA][OMs]). Our strategy exploits selective partial deuteration of the ionic species, which enables the separate evaluation of cation and anion dynamics. We demonstrate for the first time that, from the known partial relaxation rates together with the determined interionic distances and self‐diffusion coefficients, the relaxation contribution arising from cation–anion interactions can be quantified. Remarkably, this approach even allows reconstruction of the total relaxation rate observed experimentally for the fully protonated IL. This methodology provides a fundamentally new route to overcoming the limited spectral resolution of FFC NMR relaxometry at low fields. More broadly, it establishes a framework for disentangling relaxation processes in complex multicomponent systems, thereby extending the applicability of FFC NMR to more challenging classes of ILs and related materials.
Source: Magnetic Resonance in Chemistry
DOI: 10.1002/mrc.70072
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,440
Awards: GRK 2943: Spektroskopische Methoden für herausfordernde Reduktionsreaktionen – Katalytische Kupplung von CO2, G3134196772, Entwicklung einer zuverlässigen Beschreibung der Rotations und Translationsdynamik in ionischen Flüssigkeiten mittels Field Cycling und HochfeldNMR Relaxometrie sowie Molekulardynamischen Simulationen, G6998751764
OpenAlex ID: W4417038167