Shape-Dependent Photomechanical Motions of Cyanostilbene-Based Molecular Crystals

Photomechanical dynamic molecular crystals provide a platform for the transition from photo energy to mechanical motions. However, the development of modulating multiple photomechanical modes through crystal size tuning is in the preliminary stage. In this study, the shape-dependent photomechanical motions of molecular crystals based on a cyclohexyl-substituted cyanostilbene derivative (CSHe) are investigated. A series of crystals with different shapes, including ribbon, needle, and plate, are prepared from the same molecule by modulating the crystal culture conditions. These crystals exhibit excellent photo-induced mechanical behaviors caused by the efficient lattice deformation from [2 + 2] cycloaddition photoreaction in the crystal. With the variety of crystal size and shape of crystals, the crystal photomechanical motions are dominantly varied from the twisting of the ribbon to the disintegration of bulk crystals. Our work broadens the insight for developing the photoresponsive modes of dynamic stilbene molecular crystals.