Deuteron quadrupole coupling constants and rotational correlation times of N-D and O-D bonds involved in doubly ionic hydrogen bonds in ionic liquids and their mixtures by means of NMR liquid and solid state experiments

我们想要测定与离子液体(ILS)及其混合物的双离子氢键(DIHBs)有关的N-D和O-D分子载体的核磁共振质子四极耦合常数(DQCC)和旋转关联时间。通常，由于核磁共振时间尺度上的快速质子交换，需要昂贵的15N或17O增强的质子弛豫时间实验来确定准确的DQCC。为了避免合成高要求和昂贵的同位素取代化合物，我们最近开发了一种方法，根据密度泛函理论(DFT)计算的N-D DQCC和离子液体簇内N-H质子化学位移之间的关系来推导DQCC。通过对质子化学位移的简单测量，我们可以获得准确的液相DQCC。这种方法是有效的，而不受温度和溶剂的影响。作为概念的证明，我们可以证明这一关系也适用于分子液体，如氨或酰胺。在本项目中，将对阳离子的O-D/O-H键进行类似的计算。这两个关系式都适用于所研究液体中的所有N-D键或O-D键，无论是离子的还是分子的。为了进一步判断预测的DQCC，我们还将通过固体核磁共振测量固相中的这些耦合参数。可靠的DQCC是从核磁共振氚四极驰豫速率确定旋转关联时间的先决条件。利用这种方法，可以确定离子液体及其混合物的第一个可靠的单粒子旋转关联时间。他们将描述N-D和O-D键的旋转动力学，这些键涉及不同分子构型的DIHBs，如离子对或离子簇。关联时间将被确定为温度的函数，从而提供关于质子型离子液体(PILS)中非均质性的重要信息。此外，还将检验流体动力学模型对包含不同中性或离子聚集体的液体体系的适用性。第一个可靠的转动关联时间对于离子液体的力场发展也是重要的。早些时候，水和醇等分子液体已经证明了这一点。

We want to determine NMR deuteron quadrupole coupling constants (DQCCs) and rotational correlation times of N-D and O-D molecular vectors involved in doubly ionic hydrogen bonds (DIHBs) of ionic liquids (ILs) and their mixtures. Usually, due to fast proton exchange on the NMR time scale, expensive 15N- or 17O-enhanced proton relaxation time experiments are needed to determine accurate DQCCs for the liquid phase. To avoid the demanding and costly synthesis of isotopically substituted compounds, we recently developed a method for deriving DQCCs from a relation between density functional theory (DFT) calculated N-D DQCCs and N-H proton chemical shifts within clusters of ionic liquids. With simple measurements of the proton chemical shifts, we have access to accurate DQCCs in the liquid phase. This approach is valid regardless of temperature and solvent effects. As proof of concept, we could show that this relation also holds for molecular liquids, such as ammonia or amides. In this project, a similar relation will be calculated for O-D/O-H bonds of cations. Both relations are valid for all N-D or O-D bonds in the investigated liquids either being ionic or molecular. For further judgement of the predicted DQCCs, we will also measure these coupling parameters in the solid phase by means of solid state NMR. Reliable DQCCs are a prerequisite for the determination of rotational correlation times from NMR deuteron quadrupole relaxation rates. Using this approach, the first reliable single particle rotational correlation times can be determined for ionic liquids and their mixtures. They will describe the rotational dynamics for N-D and O-D bonds which are involved in DIHBs in different molecular configurations, such as ion pairs or ionic clusters. The correlation times will be determined as a function of temperature, providing important information about the heterogeneity in protic ionic liquids (PILs). Moreover, the applicability of hydrodynamic models will be tested for the liquid systems including different neutral or ionic aggregates. The first reliable rotational correlation times are also of importance for the force field development of ionic liquids. This has been demonstrated earlier for molecular liquids, such as water and alcohols.