Theoretical Study on Esipt of Flavonol Galangin Molecules in Different Solvents

Abstract

In this study employed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to investigate the photophysical properties of Galangin in two solvents, DMSO and MeOH, focusing on the mechanisms of excited-state intramolecular proton transfer (ESIPT) and intermolecular proton transfer (ESPT). Potential energy curves (PECs) and frontier molecular orbitals (FMOs) were analyzed to elucidate the charge transfer process and the detailed proton transfer mechanism of the 3-OH group in Galangin were analyzed in different solvents. The results indicated that in DMSO, ESIPT was initiated due to the disruption of strong intramolecular hydrogen bonds at the 5-OH site by DMSO molecules. In contrast, in MeOH, ESPT was facilitated through the formation of intermolecular hydrogen bonds with the solvent. Enhanced hydrogen bonding in the S1 state was confirmed by increased electron density and bond energy. Furthermore, IR vibrational spectra showed redshifts in the S1 state, indicating stronger hydrogen bonds in both solvents. These findings provide theoretical insights into the solvent-dependent photophysical behavior of flavonol derivatives and offer guidance for the design of fluorescence probes.

Keywords: Flavonols, Galangin, Hydrogen bond, ESPT, ESIPT