LAUSR

Skeletal or concave polyhedral crystals appear in a variety of synthetic processes and natural environments. However, their morphology, size, and orientation are difficult to control because of their highly kinetic growth character. We report a methodology to achieve synchronous, uniaxial, and stepwise growth of micrometer-scale skeletal single crystals from planar-chiral double-decker molecules. Upon drop-casting of a heated ethanol solution onto a quartz substrate, the molecules spontaneously assemble into standing vessel-shaped single crystals uniaxially and synchronously over the wide area of the substrate, with small size polydispersity. The crystal edge is active even after consumption of the molecules and resumes stereoselective growth with successive feeding. The resultant morphology can be packed into polycyclic aromatic hydrocarbon–like microarchitectures and behaves as a microscopic container. Description Growing crystalline containers Hierarchical crystals are often found in nature, and biological processes delicately control their growth and patterning. For synthetic systems, this process remains challenging. For example, skeletal crystals with concave morphology usually require additives and complicated temperature control. Oki et al. succeeded in growing teacup-shaped microcrystals in a controlled, uniaxial manner by casting a solution of a planar-chiral molecule on a clean quartz substrate and evaporating it, causing supersaturation and crystal growth. The authors show that despite the overall geometrical complexity of the crystal, it emerges from the highly symmetric ordering of the chiral planar molecules that stack on one another with a counterclockwise rotation of 60° along a crystallographic sixfold screw axis. —MSL A planar-chiral double-decker molecule forms skeletal concave crystals with synchronous and uniaxial growth.