Mechanochromic Luminescence from Crystals Consisting of Intermolecular Hydrogen‐Bonded Sheets

of functional groups that can form intermolecular hydrogen bonds into highly‐emissive luminophores is a promising way to induce mechanochromic luminescence. Herein, we report that a 9,10‐bis(phenylethynyl)anthracene derivative featuring two amide groups forms green‐emissive crystals based on two‐dimensional hydrogen‐bonded molecular sheets. Mechanical grinding changed the emission from green to yellow, owing to a transition from a crystalline to an amorphous phase. Infrared spectroscopy revealed that mechanical stimuli disrupted the linear hydrogen‐bonding formation. A thermal treatment recovered the original green photoluminescence.