Anisotropic bending and twisting behaviour of a twin crystal composed of a diarylethene

Abstract

Here, we found that crystals consisting of 1,2-bis(2-methyl-5-(4-undecyloxyphenyl)-3-thienyl)-perfluorocyclopentene (1a) exhibit unusual photomechanical bending. Upon irradiation with ultraviolet (UV) light, the crystal bent toward the incident light, but the velocity of the bending depended on the illumination directions. When irradiated from the left and right sides of the crystal, the velocities of the bending were different from each other. We found that the crystal is a “twin crystal”, as confirmed by X-ray crystallography. The bending mechanism of the twin crystal can be interpreted from the content of twin components, the absorption anisotropy of diarylethene molecules and the degree of the crystal twisting.