Turning on Solid‐State Fluorescence with Light

A bioinspired fluorophore that is analogous to the substrate in the bioluminescence of fireflies was prepared and reacts when exposed to weak blue LED light. Upon excitation, this material is photodecarboxylated with a nearly 81‐fold enhancement of the solid‐state emission, the fluorescence quantum yield of the product in solution is approximately 90 %, and violent disintegrative effects occur as a result of the release of carbon dioxide. Crystallographic and computational results, together with global spectral analysis of the kinetics, confirmed that most of the emission observed in the decay‐associated spectra is intrinsic to the product molecule, with only a minor contribution from an excimer through π–π stacking of the molecules in the crystal.