Confined Chiral Microenvironments in Discrete Supramolecular Assemblies.

Chirality is a fundamental feature of nature, governing the structure and function of biological systems. Translating molecular chirality into well-defined supramolecular architectures is crucial for understanding chiroptical phenomena and developing advanced chiral functional materials. In this Account, we summarize our research efforts over the past decade focused on the rational design and self-assembly of discrete chiral metallacycles and cages. We highlight how simple chiral building blocks can be programmed to spontaneously form complex two and three-dimensional architectures with confined chiral microenvironments. Our work begins with the precise construction of chiral metallacycles, including triangles, squares, and hexagons, where we demonstrate effective chirality transfer from the ligand to the metal center. These assemblies not only exhibit structural elegance but also serve as versatile platforms for studying chirality amplification. We then extend this strategy to three-dimensional chiral cages, including helicates, tetrahedra, octahedra, and nonclassical polyhedra. By engineering specific functional groups, such as NH, OH, or metal-salen sites within the confined cavities, we achieve precise control over the microenvironment. We further discuss the functional applications of these assemblies. The confined chiral spaces enable exceptional performance in enantioselective recognition, separation, and transmembrane transport, often mimicking the selectivity of natural enzymes. Moreover, we showcase how these cages function as supramolecular catalysts, where the confined nanospace significantly enhances reactivity and stereocontrol compared to nonencapsulated systems. Finally, we provide our perspective on the future challenges in this field, including the construction of nonclassical and defective structures, the hierarchical organization of discrete assemblies into extended materials, and the pursuit of biomimetic functions. This work aims to bridge the gap between molecular chirality and emergent supramolecular function, providing a comprehensive insight into the development of adaptive chiral materials.