Supramolecular Chemistry of Boron Clusters with Cyclodextrins: From Synthesis to Applications

直到2015年，我们的团队不仅发表了第一份关于其主客体络合行为的研究报告，而且还报道了与环糊精(CD)的创纪录亲和力，这使得这一研究领域不仅具有原创性，而且在概念上也很有趣，在实践中也很有前途。十二硼酸根阴离子二十面体硼簇合物((B12X12)2−，X=H，CI，BrI)在水溶液中与大分子Cd(如β-，γ-和ε-Cd)形成包合物，具有很强的结合亲和力(Ka=10^3~10^6 M^(−1))。我们根据十二硼酸根阴离子的高极化率和超杂化性质解释了它们的高亲和力，揭示了杂化效应是破坏水结构的阴离子(杂化阴离子)与疏水空穴的内在结合的一般驱动力。如此高的结合亲和力为未来的应用提供了新的机会。通过这个项目，我们希望通过探索具有式(B10X10)^2-、(B12X12)^2-、(B21H18)^-和(B12X11R)^2-的新的硼簇衍生物来加强我们对这一新兴研究领域的贡献。通过改变取代基X(H、F、Cl、Br和I)，不仅可以系统地改变团簇的大小，而且可以改变其极化率。此外，根据化学式，电荷和分子的几何形状也可以改变。拟议的研究将涵盖母体和不同官能化的CD，以模拟不同类型的分子间相互作用，这些相互作用涉及形成的主客体络合物的稳定性，以及其他潜在的宿主分子(例如，不同大小的瓜环和杯芳烃)。此外，我们还提出了新的合成方法来实现硼原子簇的单功能化(卤化和非卤化)，这将是进一步修饰原子簇和打开未来应用前景的关键。用于展示十二硼酸结合基序的力量的应用，将在本提案的背景下进行探索，包括非共价标记、表面修饰、构建刺激响应系统、手性识别和拆分以及传感。为了完成这项任务，一个研究合成化学(DG)的小组和一个研究超分子化学(WN)的小组加入了他们的互补专业知识。

The host-guest chemistry of boron cluster compounds has remained unexplored until 2015, when our team not only published the first study on their host-guest complexation behavior, but also reported record affinities with cyclodextrins (CDs), which render this field of research not only original but also conceptually interesting and practically promising. Anionic icosahedral boron clusters of the dodecaborate type ((B12X12)2− with X = H, CI, Br, I) were found to form inclusion complexes with large CDs (e.g., β-,γ-, and ε-CD) in aqueous solution with exceedingly strong binding affinities (Ka =10^3 to 10^6 M^(−1)). We have interpreted the high affinities of the dodecaborate anions based on their high polarizability and the superchaotropic nature, revealing the chaotropic effect as a general driving force for the intrinsic binding of water-structure breaking anions (chaotropic anions) to hydrophobic cavities. Such high binding affinities offer new opportunities for future applications. Through this project, we would like to strengthen our contribution to this emerging research field by exploring new boron cluster derivatives with the formulae (B10X10)^2–, (B12X12)^2–, (B21H18)^–, and (B12X11R)^2–. Through changing the substituent X (H, F, Cl, Br, and I), not only the size of the cluster, but also its polarizability, can be systematically varied. Moreover, based on the chemical formula, the charge and the molecular geometries can also be varied. The proposed study will cover the parent and different functionalized CDs in order to mimic different types of intermolecular interactions, which are involved in the stability of the formed host-guest complexes, as well as other potential host molecules (e.g., cucurbiturils and calixarenes of different sizes). Moreover, we propose novel synthetic approaches for the monofunctionalization of boron clusters (halogenated and non-halogenated), which will be essential to further modify the clusters and open the perspective of future applications. Applications which serve to demonstrate the power of the dodecaborate binding motif, and which will be explored within the context of this proposal, include non-covalent labeling, surface modifications, constructing stimuli-responsive systems, chiral discrimination and resolution, and sensing. In order to tackle this task, a group working on synthetic chemistry (DG) and a group working on supramolecular chemistry (WN) have joined their complementary expertise.