Theoretical study of solvent polarity on regulating the excited-state intramolecular proton transfer process of 2-(2′-hydroxyphenyl)benzimidazole derivative

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2025-01, Vol.458, p.115947, Article 115947
• Main Authors: Wang, Fuyang, Wang, Ye, Sun, Chaofan
• Format: Article
• Language: English
• Subjects: ESIPT; Fluorescence; Potential energy curves; Solvent polarity; TD-DFT
• ISSN: 1010-6030
• DOI: 10.1016/j.jphotochem.2024.115947

[Display omitted] •Increased solvent polarity weakens the strength of intramolecular hydrogen bond in BTEP.•Maximum emission spectrum of BTEP is blue-shifted with increasing solvent polarity and the intensity of the emission spectrum is less variable.•Both the increase in intramolecular hydrogen bond strength and intramolecular charge transfer promote the ESIPT process of BTEP.•ESIPT process of BTEP is more likely to occur in solvents with weak polarity. In this work, the solvent effect on the excited-state intramolecular proton transfer (ESIPT) mechanism of the derivative (BTEP) based on 2-(2′-hydroxyphenyl)benzimidazole (HBI) modification in cyclohexane, dichloromethane and acetonitrile solvents has been investigated by utilizing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The detailed study of the main geometrical parameters, infrared (IR) vibration spectra, and reduced density gradient (RDG) versus Sign(λ2)ρ(r) scatter plots related to intramolecular hydrogen bond (IHB) reveals that the IHB strength of BTEP is enhanced in the excited state comparing with that in the ground state and that the magnitude of the enhancement decreases as solvent polarity increased. In addition, analysis of the potential energy curves (PECs) at the S0 and S1 states revealed that the energy barrier of the ESIPT reaction increases with increasing solvent polarity. These analyses have shown that increasing solvent polarity makes the ESIPT reaction increasingly difficult, and we hope that our study can provide guidance for subsequent research into further application of BTEP to fluorescent probes.