摘要: The photochromic mechanism of 1-phenyl-3-methyl-4-(6-hydro-4-amino-5-sulfo-2,3-pyrazine)-pyrazole-5-one has been investigated using the density functional theory (DFT). The solvent effect is simulated using the polarizable continuum model (PCM) of the self-consistent reaction field theory. According to the crystal structure of the title compound, an intramolecular proton transfer mechanism from enol to keto form was proposed to interpret its photochromism. Bader's atom-in-molecule (AIM) theory is used to investigate the nature of hydrogen bonds and ring structures. Time-dependent density functional theory (TDDFT) calculation results show that the photochromic process from enol to keto form is reasonable. The conformation and molecular orbital analysis of enol and keto forms explain why only intramolecular proton transfer is possible. The results from analyzing the energy and dipole moments of enol form, transition state and keto form in the gas phase and in different solvents have been used to assess the stability of the title compound.