Insights into the translational and rotational dynamics of cations and anions in protic ionic liquids by means of NMR fast-field-cycling relaxometry.
Insights into the translational and rotational dynamics of cations and anions in protic ionic liquids by means of NMR fast-field-cycling relaxometry.
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通过 NMR 快速场循环弛豫测量深入了解质子离子液体中阳离子和阴离子的平移和旋转动力学
DOI：
10.1039/d0cp05440b
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
R. Ludwig
中科院分区：
文献类型：
--
作者：
V. Overbeck;H. Schröder;A.-M. Bonsa;K. Neymeyr;R. Ludwig
理解氢键质子离子液体（PIs）中阳离子和阴离子的平移和旋转动力学仍然是一个挑战。在这项研究中，我们确定的自扩散系数和旋转相关时间的两个离子在三乙铵基PIL的NMR快场循环（FFC）弛豫法。1H和19 F核磁弛豫色散（NMRD）曲线的全球拟合允许适当的分离到两个NMR敏感核的分子内和分子间弛豫速率，从而可靠地描述两种离子的平移和旋转运动。在室温下，阳离子的扩散系数约为6 × 10−11 m2 s−1，比阴离子的扩散系数大50%。阳离子和阴离子在两个PIL的扩散系数进行了比较，我们来自应用一个通用的色散幂律和那些已知的脉冲场梯度（PFG）NMR研究。考虑到能斯特-爱因斯坦方程，摩尔电导率由阳离子和阴离子扩散系数计算，并与直接测量的摩尔电导率相关，从而可以测定解离度。旋转相关时间τR范围从50 ps到2 ns作为温度的函数进行了比较，从高场NMR四极弛豫时间测量明确解决NH矢量的旋转，并给出洞察酸性质子迁移率。应用Stokes-Einstein和Stokes-Einstein-Debye关系将扩散系数和旋转相关时间与宏观体粘滞系数联系起来。还针对典型的PIL硝酸乙铵讨论了结果。
Understanding the translational and rotational dynamics of cations and anions in hydrogen bonded protic ionic liquids (PIls) is still a challenge. In this study, we determine self-diffusion coefficients and rotational correlation times of both ions in triethylammonium based PILs by means of NMR Fast-Field-Cycling (FFC) relaxometry. Global fits of 1H and 19F nuclear magnetic relaxation dispersion (NMRD) curves allowed proper separation into intra and inter molecular relaxation rates for both NMR sensitive nuclei and thus a reliable description of translational and rotational motion for both ions individually. The diffusion coefficients of the cations are in the order of 6 × 10−11 m2 s−1 at room temperature and about 50 per cent larger than those of the anions. The diffusion coefficients of cations and anions in both PILs were compared with those we derived from applying an universal dispersion power law and those known from pulsed field gradient (PFG) NMR studies. Considering the Nernst–Einstein equation, molar conductivities were calculated from cationic and anionic diffusion coefficients and related to directly measured molar conductivities, allowing the determination of the degree of dissociation. The rotational correlation times τR ranging from 50 ps up to 2 ns as a function of temperature were compared with those obtained from high-field NMR quadrupolar relaxation time measurements addressing explicitly the rotation of the NH vector and giving insights into the acidic proton mobility. The Stokes–Einstein and Stokes–Einstein–Debye relations were applied to relate the diffusion coefficients and rotational correlation times to the macroscopic bulk viscosity. The results were also discussed with respect to the archetypical PIL ethylammonium nitrate.
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DOI：
10.1088/0022-3719/14/4/018
发表时间：
1981-02
期刊：
Journal of Physics C: Solid State Physics
影响因子：
--
作者：
C. A. Sholl
通讯作者：
C. A. Sholl
影响因子：
4.4
作者：
Kruk, D.;Meier, R.;Roessler, E. A.
通讯作者：
Roessler, E. A.
液体中氘四极耦合常数的间接测量方法
影响因子：
1.7
作者：
M. Wendt;T. Farrar
通讯作者：
T. Farrar
影响因子：
5.7
作者：
Honegger, Philipp;Overbeck, Viviane;Steinhauser, Othmar
通讯作者：
Steinhauser, Othmar
影响因子：
5.7
作者：
Blanchard, John W.;Belieres, Jean-Philippe;Holland, Gregory P.
通讯作者：
Holland, Gregory P.