Dynamic supramolecular snub cubes

Abstract

Mimicking the superstructures and properties of spherical biological encapsulants such as viral capsids1 and ferritin2 offers viable pathways to understand their chiral assemblies and functional roles in living systems. However, stereospecific assembly of artificial polyhedra with mechanical properties and guest-binding attributes akin to biological encapsulants remains a formidable challenge. Here we report the stereospecific assembly of dynamic supramolecular snub cubes from 12 helical macrocycles, which are held together by 144 weak C–H hydrogen bonds3. The enantiomerically pure snub cubes, which have external diameters of 5.1 nm, contain 2,712 atoms and chiral cavities with volumes of 6,215 Å3. The stereospecific assembly of left- and right-handed snub cubes was achieved by means of a hierarchical chirality transfer protocol4, which was streamlined by diastereoselective crystallization. In addition to their reversible photochromic behaviour, the snub cubes exhibit photocontrollable elasticity and hardness in their crystalline states. The snub cubes can accommodate numerous small guest molecules simultaneously and encapsulate two different guest molecules separately inside the uniquely distinct compartments in their frameworks. This research expands the scope of artificial supramolecular assemblies to imitate the chiral superstructures, dynamic features and binding properties of spherical biomacromolecules and also establishes a protocol for construction of crystalline materials with photocontrollable mechanical properties. Left- and right-handed snub cubes show photocontrollable elasticity and hardness, in addition to the ability to encapsulate different small molecules in distinct compartments simultaneously, with potential applications in the development of advanced biomimetic materials.