Positive/Negative Phototropism: Controllable Molecular Actuators with Different Bending Behavior

Herein, a series of molecular actuators based on the crystals of (E)‐2‐(4‐fluorostyryl)benzo[d]oxazole (BOAF4),(E)‐2‐(2,4‐difluorostyryl)benzo[d]oxazole (BOAF24), (E)‐2‐(4‐fluorostyryl)benzo[d]thiazole (BTAF4) and (E)‐2‐(2,4‐difluorostyryl)benzo[d]thiazole (BTAF24) showed unprecedented different bending behavior under UVirradiation. BOAF4 and BTAF4 bent towards light, whereas BOAF24 and BTAF24 bent away from light.Although the chemical structures of these compounds are similar, we found out the F‒H‒C interaction wasthe main driving force for the different molecular packing in the crystals, which led to the positive/negativephototropism of the actuators. Moreover, the theoretical calculation was carried out to reveal the mechanicalproperties of the crystals. Taking advantage of the photo responsive property, we achieved the potentialapplication in pushing objects, as well as enriching and removing pollutants. This system not only achieved aclass of molecular actuators with different bending behavior through introducing different number of F atom,but also realized pushing and catching behavior within one molecule, which opens a novel gate for crystalengineering