Character and influence of hydrogen bonding on the microstructures of ionic liquids by means of neutron diffraction and molecular dynamics simulations

通过中子衍射和分子动力学模拟研究氢键特征及其对离子液体微观结构的影响

• 批准号: 450088079
• 负责人: Professor Dr. Ralf Ludwig
• 金额: --
• 依托单位: Lehrstuhl für Allgemeine Physikalische und Theoretische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/450088079?language=en
• 关键词: Character; influence; hydrogen; bonding; microstructures

In this project, we want to study the double-faced nature of hydrogen bonding in hydroxyl-functionalized ionic liquids (ILs) by means of neutron diffraction (ND) and molecular dynamics (MD) simulations. In recent experimental studies, we have shown that in this IL family, two distinct types of hydrogen bonds (HBs) coexist: The conventional HBs between cation and anion (ca) and elusive HBs between two cations (cc) that are supposed to be much weaker due to the repulsive Coulomb force between the like-charged ions. Despite this expectation, however, we observed structural motifs involving hydrogen-bonded cationic clusters in the bulk liquid and the gas phase. In preliminary ND experiments on pure hydroxyl-functionalized ILs, we have measured the distances for both type hydrogen bonds, showing that the (cc) HBs are 10 ppm shorter than the (ca) HBs despite the repulsive interaction between the cations. The double-faced nature of hydrogen bonding in hydroxyl-functionalized ILs allows tackling fundamental questions, which we address here. Firstly, mixing OH-functionalized with non-functionalized ILs provides information about the influence of OH-defects on the size and distribution of (ca) and (cc) clusters in ILs. Secondly, mixing the IL with alcohol molecules mimicking the IL cation, allows studying the liquid nanostructures upon charge-defects by changing from the ionic to the ML. Thirdly, adding a strong polar proton acceptor molecule competing for the OH-groups in the IL opens a path for controlling the HB distribution by an OH-catcher. Varying the size and distribution of hydrogen bonded clusters upon hydroxyl- and charge-defects or introducing OH-catchers, allows tuning the properties of ILs and their mixtures, which are both attracting increasing interest in science and technology. The direct determination (H…O) and (O…O) bond distances, indicating the HB strengths in hydroxyl-functionalized ionic and molecular liquids, is only accessible through ND experiments and support of MD simulations.

在这个项目中，我们希望通过中子衍射（ND）和分子动力学（MD）模拟研究羟基官能化离子液体（ILS）中氢键的双面性质。在最近的实验研究中，我们表明，在这个IL家族中，两种不同类型的氢键（HBS）共存：阳离子和阴离子之间的常规HBS（CA）之间的常规HBS以及两个阳离子（CC）之间的HBS（CC）之间的常规HB，由于类似带电的离子之间的排斥力，它们由于排斥力而弱得多。尽管如此，尽管如此，我们还是观察到涉及大体液体和气相中含有氢键的阳离子簇的结构基序。在对纯羟基功能化IL的初步ND实验中，我们测量了两种类型的氢键的距离，表明（CC）HBS（CC）HBS比（Ca）HBS Dospite短10 ppm，阳离子之间的排斥相互作用。羟基功能化IL中氢键的双面性质允许解决基本问题，我们在这里解决。首先，将OH官能化与非功能化IL混合提供有关OH-缺陷对ILS（CA）和（CC）簇的大小和分布的影响的信息。其次，将IL与模仿IL阳离子的酒精分子混合，允许通过从离子到ML更改电荷缺失时研究液体纳米结构。第三，在IL中添加强大的极性质子受体分子竞争了OH组，为OH捕获器控制HB分布的路径开辟了一条路径。在羟基和电荷缺失或引入OH捕获器上改变氢键簇的大小和分布，可以调整ILS及其混合物的特性，这两者都引起了对科学和技术的兴趣。直接测定（H…O）和（O…O）键距离，表明仅通过ND实验和对MD模拟的支持才能访问羟基官能化离子和分子液体中的HB强度。