Benzodifuranone Crystals with Solid‐State Emission Arising from the Introduction of Bulky Substituents

Benzodifuranone derivatives, structural analogues of widely studied diketopyrrolopyrrole, have been reported to show photoluminescence exclusively in solution states. Here, upon introducing bulky aromatic groups into benzodifuranone dyes, crystals with unprecedented solid‐state emission were obtained. A crystallographic analysis revealed that the emissive properties should most likely be attributed to the absence of stacking between the dye scaffolds. In addition to the solid‐state emission, the compound showed responsivity to external stimuli, i. e., luminescent mechanochromism and thermosalient effect.