Cyano-Engineered Tetraphenylethene-Based Pd2L4 Metallacages for Iodide Detection

Selective recognition of iodide remains challenging because of its large ionic radius, weak hydration, and high polarizability. Herein, we report two tetraphenylethene-based Pd2L4 metallacages featuring cyano-vinylene spacers for confined-cavity engineering and iodide recognition. Structural analysis reveals that subtle ligand variation leads to distinct supramolecular microenvironments, in which inward-oriented cyano-vinylic hydrogen atoms generate an electron-deficient cavity favorable for anion binding. Both metallacages exhibit aggregation-induced emission and pronounced photoluminescence quenching in response to iodide, with high selectivity over competing anions. Solid-state sensing strips enable rapid, concentration-dependent visual iodide detection with minimal interference from counter cations or pH variations.