Effects of solvents on excited‐state proton transfer behaviors and photophysical properties of 3NTF

Abstract

In this work, we systematically investigate the effects of solvent on the mechanism of excited‐state proton transfer and photophysical properties of 3NTF using density functional and time‐dependent density functional. The geometry of 3NTF (normal structure and isomer structure) was optimized. Based on the optimized geometry, the parameters related to hydrogen bond indicate that the hydrogen bond is strengthened in the S1 state. Further, reduced density gradient functions provide a more intuitive proof of the excited hydrogen bond strengthening mechanism. The analysis of frontier molecular orbitals shows that the charge density of the S0 and S1 states has changed significantly, which is the driving force for proton transfer in the excited state. The infrared vibrational spectra show that the hydrogen bond strength decreases with the increase of solvent polarity. The absorption and fluorescence spectra of the molecules are very sensitive to the solvent polarity. Through the analysis of the potential energy curves, it is concluded that the decrease of solvent polarity will promote the occurrence of the excited state proton transfer process.