Fig. 2: Characterization of the redox state and electrically driven operation of the [3]catenane molecular motor [3]CMM.

a, Structural formula for the oxidized state [3]CMM¹³⁺ with an optimized quantum mechanical model structure (M06-2X/6-31G* basis set, in tubular with superimposed space-filling representation) and the ¹H NMR spectrum (500 MHz, CD₃COCD₃, 298 K), in which all the proton assignments are labelled. b, X-ray single-crystal structure of the reduced state [3]CMM^7+6• depicted by tubular with superimposed space-filling representations. Solvent molecules, counterions and hydrogen atoms are omitted for the sake of clarity. c, Vis/NIR spectra of the reduced state [3]CMM^7+6• (purple) and the oxidized state [3]CMM¹³⁺ (blue) during the electrically driven operation of the molecular motor. Conditions: [3]CMM (30 μM), MeCN solution with TBAPF₆ (0.1 M) as the supporting electrolyte, reduction potential −0.5 V (versus Ag/AgCl) for 10 min, oxidation potential +0.7 V (versus Ag/AgCl) for 15 min. Insets are photographs of the two solutions in the oxidized (colourless) and reduced (purple) states. d, Absorption intensities of [3]CMM^7+6• (purple) and [3]CMM¹³⁺ (blue) at 1,122 nm, showing the reversible switching between the two redox states during each cycle. Abs, absorption; ppm, parts per million.