Photoisomerizations of 6-hydroxy-5,12-naphthacenequinone and its derivatives bearing methyl and phenyl group were theoretically investigated with density functional theory method and ab initio CIS method at the B3LYP 6-31G basis set, respectively. The obtained potential energy curves disclosed that a four-state cycle existed in the ground and excited states. It was also found that the activation energy for the methyl transfer was higher compared to the phenyl transfer, which was consistent to the experimental results that the photoisomerization of the phenyl substituted derivative was more rapid than the methyl substituted derivatives. Further hybrid time-dependent density functional theory (TD-DFT) was used to investigate the absorption and fluorescence spectra of these compounds under solvent effect condition. The calculated values were in agreement with the experimental results and the excitation condition of photochromic reactions.

Key words: naphthacenequinone, photochromism, photoisomerization, density functional theory, electronic spectra