This paper describes an electric molecular motor based on a [3]catenane, where two cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺) rings circumrotate unidirectionally around a 50-membered loop powered by electricity. The loop's design ensures highly unidirectional ring movement (85%) guided by a flashing energy ratchet, with ring interactions creating a two-dimensional potential energy surface similar to F₀F₁-ATP synthase. Unidirectionality is achieved through oscillating voltage or redox potential modulation. A [2]catenane analogue showed insufficient kinetic asymmetry for unidirectional movement, prompting the use of a second CBPQT⁴⁺ ring for symmetry breaking. This electrically driven, waste-product-free circumrotatory motion is a significant step toward surface-bound electric molecular motors.

Long Zhang, Yunyan Qiu, Wei-Guang Liu, Hongliang Chen, Dengke Shen, Bo Song, Kang Cai, Huang Wu, Yang Jiao, Yuanning Feng, James S. W. Seale, Cristian Pezzato, Jia Tian, Yu Tan, Xiao-Yang Chen, Qing-Hui Guo, Charlotte L. Stern, Douglas Philp, R. Dean Astumian, William A. Goddard III, J. Fraser Stoddart