Predesigned Cluster-Based Spacers for Versatile Luminescent Metallacages

Luminescent metal–organic cages are of great interest in contemporary research; however, their designed synthesis remains challenging. Here, we created metal-cluster-derived spacers, where emissive C₃-symmetric Cu₄ clusters have three arms modified by benzene alkynyl ligands, which are terminally functionalized by extensile −COOH and 15-crown-5-ether groups with directional coordination ability. Through vertex orientation, −COOH-functionalized cluster-based spacers coassembled with paddle-wheel Cu­(I)_xZn­(II)_2‑x(COO)₃ nodes in 3+3 mode, generating an emissive cubic cage, which subsequently gave another distorted cubic cage by synthetic modification on the nodes. Through face orientation, 15-crown-5-ether-containing cluster-based spacers capturing K⁺ ions in 3+2 mode produced an octahedral cage whose empty phase showed dual emission peaks, leading to diverse stimuli-responsive photoluminescence. This work provides new design and synthesis strategies for the integration of nodes and spacers based on metal clusters for cage materials as well as prototypes of luminescent metal-cluster cages for important sensing applications.