A nanometre-sized hexahedral coordination capsule assembled from 24 components

Molecular capsules consist of closed, hollow frameworks within which encapsulated molecules are isolated from interaction with external molecules1. In this environment, otherwise reactive molecules can be stabilized2,3,4,5. Although some molecular capsules have been prepared by conventional synthetic chemistry1, recent progress in non-covalent synthesis has allowed the creation of capsules held together by hydrogen bonds6,7,8,9. Here we report the use of transition-metal-based coordination chemistry10,11,12,13,14,15,16,17,18,19 to assemble a stable, nanometre-scale capsule from 24 small components: 18 metal ions and six triangular ligands. The capsule is roughly hexahedral and comprises six edge-sharing triangles with two metal ions on each edge. The internal space has a volume of 900 Å3 and is fully closed to all but very small molecules.