Solvent conditions effect on the excited state intramolecular proton transfer mechanism and photophysical property of 1′-hydroxy-2′-acetonaphthone: A DFT/TD-DFT analysis

Abstract

Recently, a fluorescence probe 1′-hydroxy-2′-acetonaphthone (HAN) detecting of metal ions is synthesized and characterized experimentally (Malini J, J. Photochem. Photobiol. A Chem., 2021, 418: 113431.). However, comprehensive research on its excited state intramolecular proton transfer (ESIPT) mechanism and photophysical property is required. In the present work, we select four solvents with different dielectric constant to investigate the effect on ESIPT process and photophysical property of HAN molecule. By means of the density functional theory (DFT) and time-density functional theory (TDDFT) methods, all theoretical calculations are accomplished. Through insights into the hydrogen bond geometrical parameters, infrared (IR) vibrational spectra, molecular electrostatic potential (MEP) surfaces, intramolecular hydrogen bond (IHB) strengthening mechanism can be verified, which providing powerful contribution to the occurrence of ESIPT reaction. Based on the analysis of frontier molecular orbitals (FMOs) and Mulliken’s charges and hole–electron, the intramolecular charge transfer (ICT) character is explained. Potential energy curves (PECs) reveal the proton transfer reaction take place more favorably in the S1 state under all solvent conditions. In addition, the energy barriers of QS molecule have ascended higher and higher from toluene (TOL) to sulfoxide (DMSO). The ESIPT behavior is preferred to proceed in the solvent with high dielectric constant instead of solvent with low dielectric constant.