Phenylene Cage Synthesized by Metal‐mediated Assembly of Phenylene Macrocycle and its Piezofluorochromic Behavior

A phenylene macrocycle containing two meta‐phenylene units positioned opposite each other was used as a building block to construct phenylene cages via platinum‐mediated C–C coupling. A phenylene cage (PC[10]3), consisting of three phenylene macrocycle units, was successfully synthesized and thoroughly characterized using nuclear magnetic resonance (NMR) spectroscopy and single‐crystal X‐ray diffraction. PC[10]3 exhibited significant backbone strain and displayed bright blue emission with a quantum yield of 96%. Additionally, PC[10]3 exhibited a broader and more pronounced piezofluorochromic response compared to its macrocyclic unit, undergoing a distinct photoluminescence shift from blue to yellow‐green under pressure. This work opens new avenues for designing and synthesizing hydrocarbon nanocages.