An electric molecular motor.

Macroscopic electric motors continue to have a large impact on almost every aspect of modern society. Consequently, the effort towards developing molecular motors ^1-3 that can be driven by electricity could not be more timely. Here we describe an electric molecular motor based on a [3]catenane ^4,5 , in which two cyclobis(paraquat-p-phenylene) ⁶ (CBPQT ⁴⁺ ) rings are powered by electricity in solution to circumrotate unidirectionally around a 50-membered loop. The constitution of the loop ensures that both rings undergo highly (85%) unidirectional movement under the guidance of a flashing energy ratchet ^7,8 , whereas the interactions between the two rings give rise to a two-dimensional potential energy surface (PES) similar to that shown by F _O F ₁ ATP synthase ⁹ . The unidirectionality is powered by an oscillating ¹⁰ voltage ^11,12 or external modulation of the redox potential ¹³ . Initially, we focused our attention on the homologous [2]catenane, only to find that the kinetic asymmetry was insufficient to support unidirectional movement of the sole ring. Accordingly, we incorporated a second CBPQT ⁴⁺ ring to provide further symmetry breaking by interactions between the two mobile rings. This demonstration of electrically driven continual circumrotatory motion of two rings around a loop in a [3]catenane is free from the production of waste products and represents an important step towards surface-bound ¹⁴ electric molecular motors.
(© 2023. The Author(s).)