Designing Dynamic Crystals with Multiple Flexibilities through a Cocrystal Strategy for Flexible Photo-controlled Switches

Endowing function crystals with flexibility can further extend their applications in the field of flexible smart devices. Herein, a brittle, photo-driven dynamic crystal was successfully modified into flexible dynamic crystals through a cocrystal strategy. The fluorescence and photo-response properties of the crystals were simultaneously improved. More importantly, the cocrystals can exhibit rare multiple flexibilities, including 2D elastic bending and twistable deformation properties, which have not been reported before for cocrystals. The mechanisms of 2D elastic bending and twistable properties were investigated through detailed crystallographic analysis, experimental tests, and theoretical calculations. It was found that the 2D elastic bending can be attributed to strong π-stacked columns connecting weak molecular interactions and herringbone molecular arrangements in the cocrystals. The twistable deformation properties are closely related to the different orientations of intermolecular interactions and molecular rotation without spatial hindrance. Finally, taking advantage of the multiple flexibilities of the cocrystals, a flexible photo-controlled switch was designed and tested.