Janus‐Type ESIPT Chromophores with Distinctive Intramolecular Hydrogen‐bonding Selectivity

Abstract Excited‐state intramolecular proton transfer (ESIPT)‐based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of Janus‐type ESIPT chromophores featuring distinctive hydrogen bond (H‐bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H‐bonds with imines in imine‐modified 2‐hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone‐modified HBT chromophores. Imine‐derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone‐derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H‐bonds and their impact on the ESIPT process. This Janus‐type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.