Light-Triggered Reversible Helicity Switching of a Rotor by a Photo-Responsive Plier

Controlling synchronized motion and transmission of molecular motion to a remotely located guest is not trivial. Here, we demonstrate a light-triggered, scissor-like conformational change in a molecular plier to reversibly alter the conformation and helical chirality of a noncovalently bound rotor. The plier comprises three building blocks: an azobenzene unit that controls the open-close motion of the plier upon light-activated isomerization from E to Z, a BINOL unit that serves as both a hinge and a chiral inducer and two pyridine moieties that can form a complex with the rotor guest. The light-induced conformational alteration of the plier was unequivocally demonstrated by ¹H NMR, UV-Vis, and CD spectroscopy. The open-close motion of the plier was translated to the rotor via a 1 : 1 host-guest complex. Indeed, CD spectroscopy, NMR spectroscopy, thermal back isomerization studies, and molecular modelling confirm that the light-triggered conformational alterations of the plier can induce mechanical twisting and helicity switching in the rotor.