Macroscopic Homochiral Twist Enables Continuous In Situ Rotational Movement in Photomechanical Assemblies

Various light-driven motions have been reported with molecular assemblies, yet continuous in situ rotational movement is rare, which is essential to simulate biological rotary motors and achieve efficient energy transduction. Inspired by natural helical systems, here, we introduce the chirality into the assembly and construct a macroscopic homochiral twisted assembly at the microscale. This assembly (BNP twist) rotated continuously under UV light (365 nm) irradiation. The speed of BNP twist rotation is regulated by controlling both light intensity and assembly size, and the rotation direction is affected by the geometrically unequal light exposure due to the twisted structure. This light-driven continuous mechanical rotation is due to the high distortion caused by the effective transfer and amplification of molecular isomerization by supramolecular self-assembly, as well as the kinematic advantages and geometric properties conferred by the macroscopic chiral twisted structure. Our research results provide a possible method for the design of continuous photomechanical assemblies, which are in sight to be used in light-driven mechanical systems, micro/nanorobots, and photoelectric devices.