ESIPT-active cinnamoyl pyrones are bright solid-state emitters: Revisited theoretical approach and experimental study

Excited-state intramolecular proton transfer (ESIPT) is a photophysical process that may lead to superior emission properties. For long time, cinnamoyl pyrone (CP) derivatives have been classified as non-ESIPT molecules. With the exception of those bearing strong electron-donor substituent, they considered no interest from spectroscopic point view, because are virtually not fluorescent in solution. Revisiting their behaviour solution shows complexity mechanisms involved. It appeared CPs with or weak substituents indeed undergo ESIPT, but facile access conical intersection subsequently induces non-radiative deactivation, hence extinction fluorescence When substituted by an electron-donating diethylamino group, molecules deactivate through radiative charge (ICT) state following ESIPT process. In solid state, restricted (RACI) makes most CP strongly fluorescent. Whatever strength these become good emitters ranging turquoise blue deep red. Although need extensive purification, one-step synthesis and spectacular aggregation-induced (AIE) properties make candidates for applications field AIE-probes photoluminescent materials.