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

Endowingfunction crystals with flexibility can furtherextendtheir applications in the field of flexible smart devices. Herein,a brittle, photo-driven dynamic crystal was successfully modifiedinto flexible dynamic crystals through a cocrystal strategy. The fluorescenceand photo-response properties of the crystals were simultaneouslyimproved. More importantly, the cocrystals can exhibit rare multipleflexibilities, including 2D elastic bending and twistable deformationproperties, which have not been reported before for cocrystals. Themechanisms of 2D elastic bending and twistable properties were investigatedthrough detailed crystallographic analysis, experimental tests, andtheoretical calculations. It was found that the 2D elastic bendingcan be attributed to strong & pi;-stacked columns connecting weakmolecular interactions and herringbone molecular arrangements in thecocrystals. The twistable deformation properties are closely relatedto the different orientations of intermolecular interactions and molecularrotation without spatial hindrance. Finally, taking advantage of themultiple flexibilities of the cocrystals, a flexible photo-controlledswitch was designed and tested. Endowinga brittle dynamic crystal with multiple flexibilitiesthrough a cocrystal strategy for flexible photo-controlled switches.