基于阴离子配位的手性超分子体系的构筑与多级组装

Chirality is universal in nature and living systems. Due to the relevance of chirality to many important fields, such as life, materials science, and medicine, the study of chiral phenomenon and chiral compounds has been a hot topic in related areas. Chirality at the (small) molecular level (molecular chirality) has a long history, while supramolecular chirality, which results from symmetry breaking in the arrangement of molecules through noncovalent interactions during the self-assembling process, has emerged and developed rapidly in recent years. Despite the significant progress made in the construction of chiral supermolecules, there remain some fundamental problems in this filed, e.g. the lack of efficient methods for the construction of a pure supramolecular enantiomer and evaluation of the enantiomeric purity. To get closer solutions to such problems, this proposal aims at the construction of chiral supramolecular compounds and higher level assemblies by using a new method, i.e. the anion coordination strategy. We have been working in the field of anion coordination chemistry and have established a new approach to well-defined supramolecular structures, such as triple helicates and tetrahedral cages, by employing anions as the coordination centers. In this proposed project, chirality will be introduced to these supramolecular entities. By utilization of chiral guests or solvents, one of the enantiomers can selectively form rather than the initially racemic helical or caged compounds built from achiral ligands. Alternatively, chiral ligands will be designed by attaching chiral terminal substituents (chiral carbon centers) on the ligands to assemble chiral supramolecular systems. In addition, further derivation of the ligands with functional groups such as long alkyl chains will enable assembly of higher-level chiral supramolecular systems such as polymers and gels. The mechanism of the chiral induction, transfer and amplification during the hierarchical assembling process will be studied and monitored by using multiple techniques, including NMR, CD, CPL, MS, etc. Through these efforts, we hope to explore the chirality in anion coordination and its applications in recognition of chiral guests and synthesis of new anion-coordination based materials such as gels and smart materials.

手性是自然界普遍存在的现象，涉及到生命、材料、医药等重要领域，因而一直是研究热点。手性的形成可以有多种方法，其中超分子手性构筑是一个简单有效而且适用范围广的途径。尽管通过超分子组装构筑手性体系已有很大发展，但还有一些问题尚未完全解决，如精确形成单一手性的物质及其表征还缺乏有效手段。本申请项目瞄准这些问题，力图以一种新的超分子组装策略，即‘阴离子配位组装’来实现手性超分子体系的高效构筑。申请人一直致力于阴离子配位化学的研究，在阴离子配位超分子组装方面取得了良好的成果。在已有的工作基础上引入手性，包括应用手性配体或通过手性客体（或溶剂）诱导来构筑手性阴离子配位超分子结构，如双螺旋、三螺旋、四面体笼子等；进一步对配体进行衍生化，以组装更高级的手性超分子聚合物。研究此多级组装过程中的手性诱导、传递、放大作用及其机制，借此探索阴离子配位手性的特点，并开发其在手性客体识别及凝胶软物质等方面的应用。

手性与生命现象和高性能材料的发展密切相关。超分子手性组装不仅可以更简便地构筑功能化手性材料，还可以模拟生物过程，加深对生命科学的理解。然而，通过多级组装制备复杂的手性超分子是一项巨大的挑战。《多层次手性物质的精准构筑重大研究计划》，旨在从分子到超分子再到材料，不同层面的单一镜像异构体的高效制备和作用机制的寻找。本培育项目针对该计划中“超分子和材料层次上缺少获得单一镜像异构体的高效方法”的问题，拟通过阴离子配位组装策略获得单一手性的超分子及更高级的宏观聚集体。阴离子配位驱动组装（ACDA）是近年来本课题组发展的一种新的组装策略。前期得到的阴离子配位超分子体系如三螺旋体、四面体笼等，与对应的金属配位体系类似，也具有潜在的手征性，如三螺旋的P和M对映体，以及四面体的ΔΔΔΔ和ΛΛΛΛ对映体。在没有手性因素的情况下，一般以外消旋体的形式存在。我们通过以下策略获得了单一手性超分子体系：1）配体上引入碳（点）手性片段获得单一手性的配体，通过点手性传递到配位手性，进而传递到超分子手性组装成单一手性的超分子体系；2）在外消旋的超分子笼空腔中结合手性客体，通过客体对主体诱导获得单一手性的超分子体系；3）将诱导的单一手性四面体笼用结合能力更强的非手性客体取代，实现超分子手性的记忆；4）在手性三螺旋体末端引入可调节亲疏水性的基团，通过溶剂极性的调控堆积成更高级别单一手性的宏观超分子堆积结构。.这些结果充分说明阴离子配位的超分子组装体可以很好地实现手性的精准传递和多级组装。此外，由于这些体系由多个氢键结合而成，翻转能垒低，表现出一些与金属体系不同的特殊性质，是研究超分子手性的理想载体。已发表15篇SCI论文，包括J. Am. Chem. Soc. 2篇， Angew. Chem. Int. Ed. 3篇，CCS Chem 2篇等。此外，还有部分工作在审稿或完善整理中，后期将继续提交报道。