Autonomous fuelled directional rotation about a covalent single bond

Biology operates through autonomous chemically fuelled molecular machinery¹, including rotary motors such as adenosine triphosphate synthase² and the bacterial flagellar motor³. Chemists have long sought to create analogous molecular structures with chemically powered, directionally rotating, components^4-17. However, synthetic motor molecules capable of autonomous 360° directional rotation about a single bond have proved elusive, with previous designs lacking either autonomous fuelling^7,10,12 or directionality⁶. Here we show that 1-phenylpyrrole 2,2'-dicarboxylic acid^18,19 (1a) is a catalysis-driven^20,21 motor that can continuously transduce energy from a chemical fuel^9,20-27 to induce repetitive 360° directional rotation of the two aromatic rings around the covalent N-C bond that connects them. On treatment of 1a with a carbodiimide^21,25-27, intramolecular anhydride formation between the rings and the anhydride's hydrolysis both occur incessantly. Both reactions are kinetically gated^28-30 causing directional bias. Accordingly, catalysis of carbodiimide hydration by the motor molecule continuously drives net directional rotation around the N-C bond. The directionality is determined by the handedness of both an additive that accelerates anhydride hydrolysis and that of the fuel, and is easily reversed additive³¹. More than 97% of fuel molecules are consumed through the chemical engine cycle²⁴ with a directional bias of up to 71:29 with a chirality-matched fuel and additive. In other words, the motor makes a 'mistake' in direction every three to four turns. The 26-atom motor molecule's simplicity augurs well for its structural optimization and the development of derivatives that can be interfaced with other components for the performance of work and tasks^32-36.