Theoretical Study on ESIPT for NHBQ‐NO2 and NHBQ‐NH2: A DFT/TDDFT Study

ABSTRACT Inspired by distinguished characteristics of novel optical materials, there has been significant research interest in organic molecules that present excited‐state intramolecular proton transfer (ESIPT) properties. Given the vital effects of substituent effect on molecular designs, in this study, we focus on probing into excited state behaviors of NHBQ‐NO 2 (i.e., submitted by strong electron‐withdrawing group ‐NO 2 ) and NHBQ‐NH 2 (i.e., submitted by strong electron‐donating group ‐NH 2 ). Exploring hydrogen bonding effects via photoexcitation, we verify the impact of substituent effect (‐NO 2 and ‐NH 2 ) on interactions involving photo‐induced hydrogen bonding effects, redistribution of charges, and associated phenomena related to ESIPT reaction. By comparing and quantifying the barriers for reactions in relative excited state, our results indicate electron‐donating substituent ‐NH 2 enhances the ESIPT reaction for NHBQ fluorophore.