Collaborative Research: Ionic Liquids- Cations in the Spotlight and Single Atom Changes with Large Consequences.

美国国家科学基金会化学部的化学结构、动力学和机理计划支持ASSOC的合作研究工作。克劳迪奥·马古利斯教授(P.I.)在爱荷华州大学系。和小爱德华·W·卡斯特纳教授。(共同P.I.)在系里。罗格斯大学化学和化学生物学系，新泽西州立大学。我们的目标是使用Marguis小组的理论和计算方法结合Castner小组的实验研究详细研究离子液体的结构和动力学性质。离子液体由柔性的、不对称的分子阳离子和阴离子组成。一些报告表明，对离子液体的阳离子或阴离子组分进行非常微小的修饰就可以使其性质发生巨大变化。例如，用磷原子取代四烷基铵阳离子的中心氮原子可以导致液体粘度下降两倍。我们目前对这些液体的理解并不能直接解释这些结果；我们的目标是将对这些液体的X射线和核磁共振实验与详细的分子模拟和理论分析相结合来解释这一现象。观察到的具有相同双(三氟甲基磺酰)酰胺阴离子的离子液体的X射线散射图谱非常相似。这是因为阴离子比碳氢基阳离子具有更多的富电子原子。因此，虽然阳离子可能是许多液体中最重要的组织成分，但X射线散射中的信息含量主要提供了关于阴离子的详细信息，关于阳离子的信息仅是间接获得的。我们将通过制备具有较小阴离子(如硝酸盐、二氰胺和醋酸酯)的离子液体来扭转这种情况，以便观察到的X射线散射图案主要来自阳离子的散射。这将为研究离子液体的结构提供一个新的视角。它还将有助于测试和设计更好的模拟参数。虽然这项研究是基础性的，但其结果将为离子液体的设计、测试和选择提供信息，用于一系列电解液应用以及与生物分子和组件的相互作用。这些液体为能源储存、纳米技术、生物质加工和制药研究中的许多重大挑战提供了解决方案。本科生、研究生和博士后研究人员将接受最新实验方法的培训，包括基于同步加速器的X射线散射实验、二维核磁共振光谱、分子动力学模拟以及应用于复杂液体统计物理的理论方法。

The Chemical Structure, Dynamics and Mechanisms Program of the NSF Chemistry Division supports a Collaborative Research effort by Assoc. Prof. Claudio J. Margulis (P.I.) at the University of Iowa Dept. of Chemistry and by Prof. Edward W. Castner, Jr. (co-P.I.) at the Dept. of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey. The goal is to study in detail the structural and dynamical properties of ionic liquids using a combination of theoretical and computational methods from the Margulis group with experimental investigations done by the Castner group. Ionic liquids consist of flexible, asymmetric molecular cations and anions. Several reports have shown that very small modification of either the cation or the anion components of the ionic liquid can make dramatic changes to its properties. For example replacing the central nitrogen atom of a tetralkylammonium cation by a phosphorus atom can lead to a drop in the liquid viscosity by a factor of two. Our current understanding of these liquids does not provide a straightforward explanation of these results; our goal is to combine x-ray and NMR experiments on these liquids with detailed molecular simulations and theoretical analyses to explain this phenomenon.The observed x-ray scattering patterns from ionic liquids that all share the same bis(trifluoromethylsulfonyl)amide anion are remarkably similar. This is because the anions have more electron-rich atoms than the hydrocarbon-based cations. Thus, whereas the cations may be the most important organizational components in many liquids, the information content in the x-ray scattering provides mostly detailed information about the anions with information about the cations being obtained only indirectly. We will invert this circumstance by preparing ionic liquids with smaller anions such as nitrate, dicyanamide and acetate, so that the observed x-ray scattering patterns result predominantly from scattering by the cations. This will provide a new perspective on the structure of ionic liquids. It will also help in testing and designing better parameters for simulations.While the research is of a fundamental nature, the outcomes will inform the design, testing and selection of ionic liquids for a range of electrolyte applications and interaction with biological molecules and assemblies. These liquids are providing solutions to a number of significant challenges in energy storage, nanotechnology, processing of biomass, and pharmaceutical research. Undergraduate students, graduate students and postdoctoral researchers will receive training in the latest experimental methods, including synchrotron-based x-ray scattering experiments, two-dimensional NMR spectroscopy, molecular dynamics simulations, and theoretical methods applied to the statistical physics of complex liquids.