The novel excited state intramolecular proton transfer broken by intermolecular hydrogen bonds in HOF system

2-(4-(Dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4Hchromen-4-one (HOF) was synthesized in experiment (Wang et al., Sensor. Actuat. B-Chem. 277 (2018) 484), and its photophysical and photochemical properties was reported. However the corresponding full theoretical interpretation of mechanisms is inadequate. In the present research, the intermolecular hydrogen bond structure of HOF-methanol complex (HOF-2M) was found, and mechanism of alcohols monitoring of HOF was deeply studied using the density functional theory (DFT) and time-dependent density functional theory (TDDFT). The enhancing mechanism of the excited state hydrogen bond is verified by analyzing the hydrogen bond parameters, infrared spectra and frontier molecular orbitals. Importantly, the reduced density gradient visual analysis and topological quantificational analysis confirm that the intramolecular hydrogen bond of HOF is broken by strong intermolecular hydrogen bonds of HOF-2M using the Atoms-In-Molecule theory. The obtained absorption and emission spectra are found to agree well with the experimental results and the complete quenched keto-emission in methanol and ethanol solvents provide a suitable sensing mechanism for detecting alcohols. The reaction path of the excited state intramolecular proton transfer for HOF is explained in detail through the constructed potential energy curves.