Deuteron quadrupole coupling constants and reorientational correlation times in protic ionic liquids.
Deuteron quadrupole coupling constants and reorientational correlation times in protic ionic liquids.
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质子离子液体中的氘核四极耦合常数和重定向相关时间。
DOI：
10.1039/c6cp01462c
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
R. Ludwig
中科院分区：
文献类型：
--
作者：
M. Strauch;Anne;Benjamin Golub;V. Overbeck;D. Michalik;D. Paschek;R. Ludwig
本文描述了一种精确测定三乙基丙基质子离子液体中N-D键氘核四极偶联常数χD的方法。该方法首先由Wendt和Farrar引入到分子液体中的O-D键中，并基于氘子四极偶联常数χD与质子化学位移δ(1)H之间的线性关系，该关系是由DFT计算得到的不同大小化合物簇的性质。因此，δ(1)H的测量提供了对χD的准确估计，然后可以通过核磁共振氘核四极弛豫时间测量来推导重定向相关时间τND。该方法适用于含有不同强相互作用阴离子的纯pil。所得的χD值在152 ~ 204 kHz之间变化，这取决于阳离子-阴离子相互作用的强度，氢键的作用增强了这种强度。我们发现，在dft计算中考虑色散校正只会导致χD值略有下降。确定的重定向相关时间表明，这些粒子满足极端变窄条件。τc值与测量的粘度一起提供了溶液中存在的簇的体积/大小的估计。此外，通过分子动力学（MD）模拟对相关时间τc和h键聚集体进行了表征。
We describe a method for the accurate determination of deuteron quadrupole coupling constants χD for N-D bonds in triethylammonium-based protic ionic liquids (PILs). This approach was first introduced by Wendt and Farrar for O-D bonds in molecular liquids, and is based on the linear relationship between the deuteron quadrupole coupling constants χD, and the proton chemical shifts δ(1)H, as obtained from DFT calculated properties in differently sized clusters of the compounds. Thus the measurement of δ(1)H provides an accurate estimate for χD, which can then be used for deriving reorientational correlation-times τND, by means of NMR deuteron quadrupole relaxation time measurements. The method is applied to pure PILs including differently strong interacting anions. The obtained χD values vary between 152 and 204 kHz, depending on the cation-anion interaction strength, intensified by H-bonding. We find that considering dispersion corrections in the DFT-calculations leads to only slightly decreasing χD values. The determined reorientational correlation times indicate that the extreme narrowing condition is fulfilled for these PILs. The τc values along with the measured viscosities provide an estimate for the volume/size of the clusters present in solution. In addition, the correlation times τc, and the H-bonded aggregates were also characterized by molecular dynamics (MD) simulations.