The magnetic coupling of a diarylethene with two nitronyl nitroxide compounds, which exhibits excellent photoswitching performance, was investigated by means of the density functional theory combined with broken-symmetry approach (DFT-BS) method. The calculated results verify that the magnetic coupling is changed with opening and closure of the ring. The same method was used to study model molecules of dimethyl dihydro pyrene with two nitronyl nitroxides. It was also found that the magnetic behavior of the open structures is different from that of close structure for the model molecules, hence the designed model molecules may also have the photoswitching performance.

Key words: nitronyl nitroxide, diarylethene, dimethyl dihydro pyrene, magnetic coupling, density functional theory