Phototunable Polychromatic Luster in Microcrystalline Film Using Photocyclization-Cycloreversion and Photochemical Side Reactions of Diarylethene

We report a phototunable polychromatic luster material based on photocyclization-cycloreversion and photochemical side reactions of diarylethene. Through recrystallization, the open-ring isomers formed plate-like microcrystals, which were then laminated to form a film. The silver-colored textured film was produced through a combination of the absence of absorption in the visible light region of diarylethene and specular reflection from the surface of the stacked microcrystals. This film showed a change in color to navy blue due to the generation of closed-ring isomers by the photocyclization of diarylethene upon UV light irradiation. The film reverted to its original color upon visible light irradiation due to the photocycloreversion reaction of the diarylethene. Further UV light irradiation of the navy blue film produced reddish-purple photounresponsive fused-ring isomers by a photochemical side reaction. Accordingly, a phototunable polychromatic luster film was achieved by light manipulation of open-, closed-, and fused-ring isomers of diarylethene.