Enhanced molecular spur gear dynamics can be achieved through a careful selection of constituent molecular components that favorably position the two gears in a meshed configuration and result in high gearing fidelity. Here we report the synthesis of a new macrocyclic molecular spur gear that utilizes a bibenzimidazole and naphthyl diphosphine gold complex stators which position symmetric 9,10-diethynyl triptycene cogs at the optimal distance for gearing. The formation of the macrocycle and proper alignment of the triptycene cogs were confirmed with microelectron diffraction, but gearing dynamics were not observable with variable-temperature <sup>1</sup>H NMR. To explore the effect of macrocyclization, we used a combination of molecular dynamics (AMBER) and metadynamics (NAMD) simulations. The calculated barriers for gearing and slippage were ca. 4 kcal/mol and ca. 9 kcal/mol, respectively, and the system was characterized by enhanced gearing fidelity achieved by rigidification of the structure that locks the triptycenes in the preferred orientation for gearing.

Towards molecular spur gears: The importance of macrocyclization on gearing fidelity

ACS Spring Meeting 2021

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