Detecting and quantifying doubly hydrogen bonded anionic dimers in ionic liquids

检测和定量离子液体中的双氢键阴离子二聚体

• 批准号: 470038970
• 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/470038970?language=en
• 关键词: Detecting; quantifying; doubly; hydrogen; bonded

Dicarboxylate species including both dicarboxylate anions and dicarboxylic acids are mostly relevant in biological, atmospheric and industrial processes. The use for reception, hosting, complexation or sensing strongly depends on non-covalent bonding, which is a paradigm of supramolecular chemistry. In this project, we want to synthesize and characterise ionic liquids, including trialkyl ammonium cations and singly deprotonated dicarboxylic acid anions. The idea is to design hydrogen bonded structural motifs in the liquid phase, strengthened or weakened by attractive or repulsive Coulomb interactions. The key motif includes the intriguing double hydrogen bonded cyclic arrangement between the carboxyl groups of two anions, wherein short-range directional hydrogen bonding overcomes the long-range repulsive Coulomb forces, monitored by varying the distance between the carboxyl and carboxylate groups within each anion. We have charge-assisted +NH…O− and charge-opposed −OH···O− single or double hydrogen bonds that control aggregation and dynamical properties of these model ionic liquids. The non-covalent forces and hydrogen bonding arrangements will be studied by far infrared (FIR) and terahertz (THz) spectroscopy that allow addressing the vibrational signatures of the intermolecular hydrogen bonds of varying strength directly. For understanding the influence of hydrogen bonding on the dynamics, we measure the deuteron NMR relaxation times of cations and anions. We compare the measured spectroscopic properties such as IR frequencies, NMR chemical shifts and quadrupole coupling constants with calculated properties from quantum chemical calculations of complexes and aggregates showing similar structural motifs and bonding. The spectroscopic descriptors will be analysed by means of the natural bond orbital (NBO) approach, revealing the correlation between these properties. A final but ultimate goal is stripping the counter ions from the neutral species for isolating the pure anionic dimers from these ionic liquids, providing the first thermodynamically stable dimers of like-charged ions detected in the gas phase by means of cryogenic ion vibrational (CIV) spectroscopy.

包括二羧酸根阴离子和二羧酸在内的二羧酸根物质主要与生物、大气和工业过程相关，其用于接收、容纳、络合或传感很大程度上依赖于非共价键合，这是超分子化学的范例。我们想要合成和表征离子液体，包括三烷基铵阳离子和单去质子化的二羧酸阴离子，其想法是设计氢键结构。液相中的基序，通过吸引或排斥库仑相互作用增强或减弱关键基序包括两个阴离子的羧基之间有趣的双氢键环状排列，其中短程定向氢键克服了长程排斥库仑力。 ，通过改变每个阴离子内的羧基和羧酸根基团之间的距离来监测我们有电荷辅助的 +NH…O− 和电荷相反的 -OH−O− 单氢键或双氢键来控制。这些模型离子液体的聚集和动力学特性将通过远红外（FIR）和太赫兹（THz）光谱来研究，这些光谱可以直接解决不同强度的分子间氢键的振动特征。为了了解氢键对动力学的影响，我们测量了阳离子和阴离子的氘核核磁共振弛豫时间，并比较了测量的光谱特性，例如红外频率、核磁共振。化学位移和四极耦合常数以及通过对具有相似结构基序和键合的复合物和聚集体进行量子化学计算而计算出的特性将通过自然键轨道（NBO）方法来分析光谱描述符，揭示这些特性之间的相关性。最终但最终的目标是从中性物质中剥离抗衡离子，以便从这些离子液体中分离出纯阴离子二聚体，提供第一个热力学稳定的同电荷离子二聚体通过低温离子振动 (CIV) 光谱在气相中检测。