London Dispersion Interactions inside Macrocycles

我们建议研究伦敦色散相互作用(LDI)对大环分子识别过程的贡献，特别是对其内腔化学反应的控制。CBN是分子容器类型的水溶性大环宿主分子，即它们能够将大量的有机客体包裹在其疏水空腔中。CBN内腔内结合的驱动力主要可以追溯到疏水效应，但LDI是一个重要的调节剂。在最初的六条实验研究路线中，有五条将在第二项目阶段进一步进行：1)在我们对惰性气体(He、Ne、Ar、Kr和Xe)与最小的CBN同系物CB5结合时LDI进行量化的基础上，我们计划研究不同的对接阳离子在生成的CB5·惰性气体·阳离子络合物中调节LDI的潜力。2)我们将扩展我们对强极化(B12X12)2-型硼酸簇合物与取代碳硼烷的高亲和力结合的研究，与双阴离子的硼酸盐簇合物不同，它具有中性核。为了剖析LDI的溶剂效应，我们还将研究这类络合物的溶剂同位素效应。3)作为超分子催化的一个例子，我们研究了环戊二烯在CB7中的二聚反应，发现反应速率提高了百万倍；本研究将扩展到甲基环戊二烯，将化学选择性引入到催化反应中。4)我们建议评估气相中包合物和排斥络合物的相对丰度，作为一种有趣的方法来研究LDI。通过合作，我们已经开始研究气相中含有CB6的一系列有机铵离子。为了进行直接比较，在优先方案的第一阶段，我们已经测定了水中铵离子与CB6的结合常数。5)还将考察气相中CBN大环的反转过程，认为这是由分子内LDI驱动的。在整个项目中，将使用核磁共振光谱、等温滴定量热法、染料置换滴定、有机合成和量子化学计算来确定结合亲和力和热力学参数，从而评估LDI的重要性。

We propose to investigate the contribution of London dispersion interactions (LDI) to the molecular recognition process of macrocycles, prominently cucurbit[n|urils (CBn) and to the control of chemical reactions inside their inner cavity. CBn are water-soluble macrocyclic host molecules of the molecular container type, that is, they are able to encapsulate numerous organic guests inside their hydrophobic cavity. The driving force for binding inside the inner cavity of CBn is primarily traced back to a hydrophobic effect, but LDI present an important modulator. Out of the original six experimental lines of investigation, five will be further pursued in the second project phase: 1) Building up on our quantification of LDI in the binding of noble gases (He, Ne, Ar, Kr, and Xe) to the smallest CBn homologue, CB5, we plan to study the potential of different docking cations to modulate LDI in the resulting CB5•noble gas•cation complexes. 2) We will extend our investigation on the high-affinity binding of strongly polarizable borate clusters of the type (B12X12)2– to substituted carboranes, which in contrast to the dianionic borate clusters possess a neutral core. In order to dissect solvent effects from LDI, we will also study the solvent isotope effect for this type of complexes. 3) As an example of supramolecular catalysis, we have investigated the dimerization of cyclopentadiene inside CB7, for which we have found a million-fold rate enhancement; this study will be extended to methylcyclopentadiene to introduce chemoselectivity into the catalytic reaction. 4) We propose to assess the relative abundance of inclusion versus exclusion complexes in the gas phase as an interesting approach to study LDI. Through collaborations, we have started to investigate a series of organic ammonium ions with CB6 in the gas phase. For direct comparison, we already determined the binding constants of the ammonium ions to CB6 in water during the first phase of the priority programme. 5) The inversion process of CBn macrocycles in the gas phase will also be examined, which is thought to be driven by intramolecular LDI. Throughout the project, NMR spectroscopy, isothermal titration calorimetry, dye displacement titrations, organic synthesis and quantum-chemical calculations will be used to determine the binding affinities as well as thermodynamic parameters and, thus, to evaluate the importance of LDI.