A giant cuboctahedron based on imidazolium-terpyridine spacer

Abstract

Giant supramolecular polyhedra are fascinating because of their large cavity, with applications in enzyme-mimetic catalysis, host-guest chemistry, and drug delivery. We report a coordination-driven, cuboctahedron-shaped, imidazolium-terpyridine-based supramolecular cage structure of about 7.3 nm diameter consisting of 12 ligands, 24 Zn 2+ ions, and 60 or 72 anions. The steric hindrance effect from chains on the imidazolium group keeps it perpendicular to the central linkage, which readily undergoes endohedral or exohedral decoration in functionalization. A reversible pH-controlled ring closure and opening reaction of the imidazolium ligand leads to a supramolecular fusion process from a triangular prism to a cuboctahedron. The compounds were characterized unambiguously by NMR, ESI-TWIM-MS, gMS 2 , Cryo-EM, and synchrotron X-ray diffraction techniques. Being readily modifiable through endo and exo pathways, the cages may provide a platform for the investigation of the biological mimic systems, confined nanotechnology, and confined molecular arrangements. • Steric hindrance drives the formation of giant cuboctahedron-shaped structures • pH-induced ring closure/opening of imidazolium leads to in situ structural transformation • Anchored groups within the cage facilitate endo-/exohedral functionalization Accessing giant supramolecular cages capable of structural transformation and straightforward functionalization is a challenge. Tang et al. report a giant terpyridine-based cuboctahedron with modifiable sites pre-organized by rotatable imidazolium motifs, which undergoes structural conversion from triangular prism to cuboctahedron at low pH.