Theoretical studies on fluorescence of phenol and 1-naphthol in both acid and alkali solutions

The molecular structures of the ground state and the first singlet excited state for C6H5OH2+, C6H5OH, C6H5O−, C10H7OH2+, C10H7OH and C10H7O−, the forms of phenol and 1-naphthol in acid and alkali solutions, were optimized by ab initio HF and configuration interaction with singlet excitations (CIS) method, respectively. Their fluorescent spectra were obtained by the time-dependent density functional theory (TD-DFT) using the B3LYP method with the 6-31+G (d) basis set. The frontier molecular orbital characteristics, fluorescent spectrum and proton affinities had been analyzed systematically in order to study different fluorescence of phenol and 1-naphthol in acid and alkali solutions. It was found that C6H5OH and C6H5OH2+ are the main forms of phenol in acid solution, but C6H5O− in alkali solution; C10H7OH and C10H7O− are the main forms of 1-naphthol in alkali solution, but C10H7OH2+ in acid solution. The calculated results are in good agreement with the experimental data.