A time‐dependent density functional theory study on the excited state behavior of a novel T2(OH)B molecule

Abstract

AbstractA novel pH‐sensitive fluorescent probe T2(OH)B was selected to theoretically investigate its excited state hydrogen bonding effects and excited state intramolecular proton transfer (ESIPT) process. First, it was verified that one intramolecular hydrogen bond is formed spontaneously in T2(OH)B itself. Given the geometrical changes, we further confirm that the hydrogen bond should be strengthened in the first excited state. When it comes to the photoexcitation process, we present the charge redistribution around hydrogen bonding moieties facilitate the ESIPT tendency. The increased electronic densities around acceptor promote the attraction of hydrogen protons. The potential energy barrier in the constructed potential energy curves reveals that the ESIPT process of the T2(OH)B system should be ultrafast. And comparing several nonpolar solvents, we deem solvent polarity plays little role in the ESIPT reaction. Furthermore, we also search the S1‐state transition state structure along with the ESIPT path, based on which we simulate the intrinsic reaction coordinate path. We not only confirm the ESIPT mechanism presented in this work but also clarify the ultrafast excited state process and explain previous experiment. We sincerely hope that our theoretical work could guide novel applications based on the T2(OH)B system in future.