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

We report the design and synthesis of indanone derivatives 1-4 with RR'N-H⋯OC intramolecular hydrogen bonds, in which ESIPT takes place and its dynamics and thermodynamics correlate with H-bond strength, facilitated by electron-withdrawing R' groups. Compound 4 (R' = COCF) shows mechanically induced ESIPT for the first time, where -CF⋯HN- interaction plays a key role in the non-centrosymmetric crystal packing.