Recently, the fluorescent phenomena of a new excited state intramolecular proton transfer (ESIPT) based fluorophore 3-hydroxy-2-(naphthalen-2-yl)-4H-chromen-4-one (HFN) has been reported experimentally. However, the first-hand dynamic information of its ESIPT process is still lacking theoretically. Based on density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, the luminescent features and ESIPT processes of HFN and its two derivatives were studied in detail. Two HFN derivatives, 3-mercapto-2-(naphthalen-2-yl)-4H-chromen-4-one (TFN1) and 3-hydroxy-2-(naphthalen-2-yl)-4H-chromene-4-thione (TFN2) were obtained by replacing the oxygen atom of proton donor and proton acceptor in HFN with sulfur atom, respectively. The changes and effects of fluorescent properties and ESIPT process generated by different proton donors and proton acceptors are demonstrated. The simulated maximum absorption and emission peaks of HFN are well consistent with the experimental data. After replacing the oxygen atoms in proton donor and proton acceptor with sulfur atoms, the absorption wavelength of HFN slightly blue-shifts and red-shifts, respectively. And the fluorescence wavelengths of HFN obviously red-shift. The S-0 -> S-1 transitions of HFN and TFN1 are dominated by pi pi* charge transfer transition, whereas the S-0 -> S-1/S-0 -> S-2 transition of TFN2 is a mixed charge transfer transition of n pi* and pi pi*. The substitution of oxygen atom by sulfur atom in the proton donor or proton acceptor of HFN obviously decreases or increases the ESIPT barrier, due to its stronger proton-donating ability of S-H group or weaker proton-accepting ability of sulfur atom, respectively.
