A combination of temperature dependent Fast Field-Cycling (FFC) relaxometry and high-resolution NMR spectroscopy provides more than five orders of magnitude in frequency range for studying translational and rotational dynamics of ionic liquids. However, to make use of this broad frequency range, certain requirements have to be met: The viscosity of the liquid has to be of the right order of magnitude, and the material has to exhibit a sufficiently broad liquid range. In addition, NMR sensitive nuclei have to be present (ideally) on both, cation and anion, and appropriate relaxation models properly describing the molecular dynamics have to be available. For the latter, Molecular Dynamics (MD) simulations are ideally suited to suggest meaningful relaxation models. In this study we employ the protic ionic liquid triethylammonium bis(trifluoromethylsulfonyl)-imide [TEA][NTf₂] as model compound to gain insight into details of the molecular dynamical processes. By addressing different NMR sensitive nuclei on both ions, ¹H nuclei on the triethylammonium cation, and ¹⁹F on the NTf₂ anion, we are able to obtain translational dynamics as well as rotational dynamics for both species at the same time. The obtained temperature dependent translatoric diffusion coefficients are consistent with our MD simulations, and are found to be in agreement with data reported in the literature. In addition, two types of NMR relaxation processes are employed to investigate the intramolecular relaxation: (1) dipolar relaxation at low frequencies (employing FFC) addressing ¹H and ¹⁹F nuclei, and (2) quadrupolar relaxation at high frequencies addressing ²H nuclei. In near quantitative agreement with MD simulations, we show that both, dipolar relaxation obtained via FFC and quadrupolar relaxation obtained via high-field NMR are leading to consistent rotational correlation times, suggesting that the rotational motion of the cation is dominantly isotropic. Hence, the intramolecular ¹H relaxation rate of the cation determined via FFC can be appropriately expressed by a single rotational correlation time, compatible with the Bloembergen Purcell Pound (BPP) approach. MD simulations of the NTf₂ anion, however, suggest that its reorientational dynamics is strongly anisotropic. Consequently, the proper description of the intramolecular ¹⁹F relaxation rate of the anion requires a more complex model beyond the BPP approach employing at least two correlation times: By taking internal rotation of the CF₃ groups into account, we are able to determine correlation times compatible with our MD simulations.

温度相关的快速场循环（FFC）弛豫测定法和高分辨率NMR光谱相结合，可为研究离子液体的平移和旋转动力学提供超过五个数量级的频率范围。但是，要利用这一宽泛的频率范围，必须满足某些要求：液体的粘度必须处于正确的数量级，并且材料必须具有足够宽的液体范围。此外，必须在阳离子和阴离子上都（理想地）存在NMR敏感核，并且必须有适当描述分子动力学的适当弛豫模型。对于后者，分子动力学（MD）模拟非常适合建议有意义的松弛模型。₂ ]作为模型化合物，可深入了解分子动力学过程的细节。通过处理两个离子上不同的NMR敏感核，三乙基铵阳离子上的¹ H核和NTf ₂阴离子上的¹⁹ F ，我们可以同时获得两种物质的平移动力学和旋转动力学。获得的温度相关的平移扩散系数与我们的MD模拟一致，并且发现与文献中报道的数据一致。此外，两种类型的NMR弛豫过程用于研究分子内弛豫：（1）低频偶极弛豫（采用FFC），其寻址范围为¹ H和¹⁹F核，和（2）在高频处的四极弛豫，寻址² H核。与MD模拟几乎定量一致，我们表明，通过FFC获得的偶极弛豫和通过高场NMR获得的四极弛豫均导致一致的旋转相关时间，这表明阳离子的旋转运动主要是各向同性的。因此，通过FFC测定的阳离子的分子内¹ H弛豫速率可以通过单一旋转相关时间来适当表示，这与Bloembergen Purcell Pound（BPP）方法兼容。但是，NTf ₂阴离子的MD模拟表明，它的重取向动力学是强烈各向异性的。因此，对分子内的正确描述阴离子的¹⁹ F弛豫速率需要采用至少两个相关时间的BPP方法之外的更复杂的模型：通过考虑CF ₃基团的内部旋转，我们能够确定与MD模拟兼容的相关时间。