The indanone N–H type excited-state intramolecular proton transfer (ESIPT); the observation of a mechanically induced ESIPT reaction

We designed and synthesized indanone derivatives with ESIPT, correlated to H-bond strength. Compound 4 shows mechanically induced ESIPT for the first time, with –CF 3 –HN– interactions crucial for non-centrosymmetric crystal packing.