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

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