A Reversible Synthetic Rotary Molecular Motor

TLDR

The minimalist [2]catenane flashing ratchet design allows mechanistic comparison with the Smoluchowski‑Feynman ratchet and pawl. The study describes the circumrotation of a submolecular fragment in either direction within a synthetic molecular structure. The motor’s motion is driven by biased Brownian displacements that are kinetically captured and directionally released, with rotation sense determined by the sequence of orthogonal chemical transformations. Even without external work or net energy input, directional rotation requires finite energy conversion, whereas nondirectional rotation does not.

Abstract

The circumrotation of a submolecular fragment in either direction in a synthetic molecular structure is described. The movement of a small ring around a larger one occurs through positional displacements arising from biased Brownian motion that are kinetically captured and then directionally released. The sense of rotation is governed solely by the order in which a series of orthogonal chemical transformations is performed. The minimalist nature of the [2]catenane flashing ratchet design permits certain mechanistic comparisons with the Smoluchowski-Feynman ratchet and pawl. Even when no work has to be done against an opposing force and no net energy is used to power the motion, a finite conversion of energy is intrinsically required for the molecular motor to undergo directional rotation. Nondirectional rotation has no such requirement.