Heat-induced ʻparallelʼ to ʻorthogonalʼ switching of fluorophores and reversible luminescence changes in divinylbenzene-benzoxazole crystals

Organic crystals that exhibit reversible solid-state luminescence triggered by heat stimulus have garnered great research interest in recent years. In this work, we demonstrate thermoresponsive, reversible color and photoluminescence switching in divinylbenzene-benzoxazole derivatives. The fluorescence switching is caused by differential chromophore packing and the resulting charge transfer On/Off states induced by heat. It is noteworthy that the reversibility, range of colors, and transition temperature associated with the luminescence switching are dependent on the length of the alkyl chains. Our results suggest that controlling charge-transfer interactions in chromophore assemblies may offer a versatile approach for creating functional organic materials with switchable, high-contrast solid-state luminescence. These findings have implications for the development of sensors, data storage devices, dynamic optical materials, and security inks.