Supramolecular Construction of a [16]‐Imidazolium Cage via a Quadruple [2+2] Photocycloaddition and Its Selective Fluorescent Recognition of Pyranine (HPTS).

Polyimidazolium‐based cages are considered promising materials based on their fascinating properties and potential applications. These three‐dimensional functional structures are highly desirable for the recognition of particular guest molecules, however, their synthesis remains challenging. In this work, we have designed and synthesizes a pure [n]‐imidazolium (n=16) cage, the hexadecakisimidazolium salt H16‐2(PF6)16, from tetragonal octakisimidazolium salt H8‐1(PF6)8. The synthetic method involves formation of metal‐carbene templates, a quadruple photochemical [2+2] cycloaddition reaction and subsequent removal of metal ions. Specifically, the synthesized cage, featuring sixteen imidazolium moieties, demonstrated high efficiency for the selective fluorescent recognition of 8‐hydroxy‐1,3,6‐pyrene trisulfonate (HPTS). The present work not only further develops the metal‐carbene template strategy by exploiting a new type of polyimidazolium cage, but also provides encouraging prospects for the design of versatile imidazolium‐based functional acceptors. [ABSTRACT FROM AUTHOR]