A Diverse Array of Large Capsules Transform in Response to Stimuli

The allosteric regulation of biomolecules, such as enzymes, enables them to adapt and alter their conformation to fit specific substrates, expressing different functionalities in response to stimuli. Different stimuli can also trigger synthetic coordination cages to change their shape, size, and nuclearity by reconfiguring the dynamic metal-ligand bonds that hold them together. Here we demonstrate an abiological system consisting of different organic subcomponents and Zn^II metal ions, which can respond to simple stimuli in complex ways. A Zn^II₂₀L₁₂ dodecahedron transforms to give a larger Zn^II₃₀L₁₂ icosidodecahedron through subcomponent exchange, as an aldehyde that forms bidentate ligands is displaced in favor of one that forms tridentate ligands together with a penta-amine subcomponent. In the presence of a chiral template guest, the same system that produced the icosidodecahedron instead gives a Zn^II₁₅L₆ truncated rhombohedral architecture through enantioselective self-assembly. Under specific crystallization conditions, a guest induces a further reconfiguration of either the Zn^II₃₀L₁₂ or Zn^II₁₅L₆ cages to yield an unprecedented Zn^II₂₀L₈ pseudo-truncated octahedral structure. The transformation network of these cages shows how large synthetic hosts can undergo structural adaptation through the application of chemical stimuli, opening pathways to broader applications.