The substituent and solvent effect on the salicylaldehyde-based azine ESIPT fluorophores

In this study, the mechanism of the excited state intramolecular proton transfer (ESIPT) process in thedonor-acceptor-structured salicylaldehyde-based unsymmetrical azine dyes L۱-L۳ was investigated by densityfunctional theory (DFT) and time-dependent density functional theory (TD-DFT) methods based on PBE۰functional and ۶-۳۱++g(d,p) basis set. Upon photoexcitation the intramolecular hydrogen bond strength wasenhanced at the S۱ state. The influence of electron-donating (−NH۲) and electron-withdrawing (–CN) groups onthe photophysical properties of these molecules was studied in the gas phase and three solvents with differentpolarities. The appearance of dual fluorescence emission bands in both gas phase and solution of enol and ketoforms of these dyes confirmed the occurrence of ESIPT in all the compounds in good agreement with thereported experimental results.

کلیدواژه ها:

ESIPT ، azine dye ، DFT ، TD-DFT