Photochromic diarylethene molecules and crystals

Some of the diarylethene derivatives were found to undergo photoisomerization reactions between two isomers even in the single-crystalline phase. The two isomers have different electronic as well as geometrical structures. The electronic structure change induces the reversible color change of the crystal. Single crystals composed of three different kinds of diarylethenes having similar geometrical structures, bisoxazolylethene, bisthiazolylethene, and bisthienylethene have been prepared. The crystals exhibited multicolor photochromism. The colorless crystals turned yellow, red, and blue upon irradiation with the appropriate wavelength of light. The geometrical structure change of component diarylethene molecules in crystals induces reversible surface morphology as well as shape and size changes of the crystals. The photoinduced geometrical structure changes of the molecules in the densely packed crystals were successfully linked to the macro-scale mechanical motion of the solid crystals and resulted in the net task of launching a tiny silica particle.