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• Firstly locate a more reasonable structure for the product of DHADC reacted with CN−. • A new fluorescence quenching mechanism for DHADC has been proposed. • Photo-induced hydrogen bonding variations have been explored. In this work, we investigated the fluorescence mechanism of the probe (E)-3-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2,3-dihydrothiophene-2-carboxamide (DHADC) for both Zn2+ and CN− by using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Utilizing the constructed potential energy curves both in the ground and excited states as a function of the distance of N2···H1, the proton transfer process of DHADC has been explored. According to the calculated spectra, another more reasonable structure of DHADC-CN for the product of DHADC responding to CN− has been proposed. All of the simulated absorption and emission spectra in this work are in agreement well with those in the experiment. Furthermore, the excited state decay picture and the fluorescence quenching mechanism of DHADC , as well as the fluorescence mechanism for Zn2+ and CN− have been fully explored. [ABSTRACT FROM AUTHOR]