A Rotary Molecular Motor Gated by Electrical Energy

DFT calculations predict that the chiral pentiptycene derivative E-1 possesses distinct rotational potential energy surfaces in the neutral vs the radical anionic (E-1•–) form such that continued electrochemical switching between E-1 and E-1•– could lead to a directional rotation of the pentiptycene rotor about the exocyclic C–C bond. The time scale of random Brownian rotation is ∼106 s for E-1 and ∼170 s for E-1•– at 150 K, and thus a switching time scale of 0.2 s could readily bias the rotation direction to >99% at 150 K. The synthetic feasibility, line-shape analysis on the VT 1H NMR spectra, and electrochemical redox switching of E-1 are demonstrated.