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

近年来，残馀偶极偶联在蛋白质和有机物结构解析中的作用越来越重要。取向介质在这方面起着关键作用：偶极耦合是各向异性的NMR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NMR相互作用的NMR实验通常在液晶或各向异性溶胀凝胶中进行。迄今为止使用的大多数系统都有一个共同点，即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，这导致重大挑战。为了解决这个问题，我们开发了第一种基于有机溶剂中的超分子聚合物的溶致液晶，其可用作取向介质。用于此目的的1，3，5-苯三甲酰胺（BTAS）是低分子量的单体化合物，其在溶液中自组装成大堆叠（由于氢键和π-π堆叠）。这些叠层的行为-在更广泛的意义上-类似于经典的聚合物链，包括它们的形式各向异性，这是建立液晶行为所必需的。超分子聚合物作为取向介质的应用中的一个巨大挑战是潜在的自缔合过程的动态性质：溶剂、分析物或杂质的干扰效应会对自缔合过程产生负面影响，从而对所获得的取向介质产生负面影响。这甚至会导致各向异性特性的破坏。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。文献提供了聪明选择取代基的起点。因此，该研究项目的目的是制备和测试已知的，以及开发新型取代的BTA，用于在有机溶剂中用作取向介质，以建立已知的基于聚合物的系统的通用替代品。

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.