Development of novel supramolecular alignment media based on 1,3,5-benzenetricarboxamides (BTAs)

近年来，残余偶极偶联在蛋白质和有机结构分析中越来越重要。对准介质在这方面起着关键作用：偶极耦合是各向异性核磁共振相互作用，在各向同性条件下无法观察到。因此，用于观察各向异性核磁共振相互作用的核磁共振实验通常在液晶或各向异性膨胀凝胶中进行。到目前为止使用的大多数系统都有一个共同点，那就是它们都是基于经典的聚合物材料。就复杂和/或耗时的制备和纯化而言，这导致了重大挑战。为了解决这一问题，我们在有机溶剂中开发了第一个基于超分子聚合物的溶致液晶，它可以用作取向介质。用于此目的的1,3,5-苯三羧基酰胺（BTAS）是低分子量的单体化合物，其在溶液中自组装成大堆栈（由于氢键和pi-pi-堆叠）。从更广泛的意义上说，这些堆栈的行为类似于经典的聚合物链，包括它们的各向异性，这是建立液晶行为所必需的。应用超分子聚合物作为定位介质的一个巨大挑战是潜在自结合过程的动态性质：溶剂、分析物或杂质的干扰效应会对自结合过程产生负面影响，从而对获得的定位介质产生负面影响。这甚至会导致各向异性的破坏。缓解这些困难的一个出发点是所使用的BTA的结构。它包含一个主要负责自组装的核心和一个原则上可以自由选择的取代基。文献提供了巧妙选择取代基的起点。因此，本研究项目的目的是制备和测试已知的，以及开发新的替代bta，作为有机溶剂中的对准介质，以建立已知聚合物基系统的通用替代品。

In recent years residual dipolar couplings became more and more important in protein as well as organic structure elucidation. Alignment media play a key role in this respect: Dipolar couplings are anisotropic NMR interactions, which are not observable under isotropic conditions. Thus, NMR experiments for the observation of anisotropic NMR interactions are usually conducted either in liquid crystals or in anisotropically swollen gels. Most systems used so far have in common, that they are based on classic polymeric materials. This leads to significant challenges as far as a complicated and/or time consuming preparation and purification is concerned. To provide a solution for this problem we have developed the first lyotropic liquid crystals based on supramolecular polymers in organic solvents, which can be used as alignment media. The 1,3,5-benzene tricarboxamides (BTAS) used for this purpose are monomeric compounds of low molecular weight, which self-assemble in solution to large stacks (due to hydrogen bonding and pi-pi-stacking). These stacks behave – in the broader sense – analogously to classic polymeric chains, including their form anisotropy which is necessary for the establishment of a liquid crystalline behavior.A formidable challenge in the application of supramolecular polymers as alignment media is the dynamic nature of the underlying self-association process: disturbing effects of the solvent, the analyte or of impurities can have a negative impact on the self-association process and thus on the alignment medium obtained. This can even lead to the break-down of anisotropic properties. One starting point to alleviate these difficulties is the structure of the BTA used. It contains a core, which is mainly responsible for the self-assembly and a substituent, which can – in principle - be chosen freely. Starting points for a clever choice of substituents are provided by the literature. The aim of this research project is thus the preparation and testing of known, as well as the development of novel substituted BTAs for the use as alignment media in organic solvents to establish a versatile alternative to the known polymer-based systems.