Supramolecular order controls the rotation frequency of artificial molecular motors

Artificial molecular motors convert light into rotary motion and are central components of synthetic molecular machineries. Their rotation frequency is key to their performance and is typically rationalized in terms of intrinsic molecular structure and solvent viscosity, while the influence of supramolecular organization remains largely unexplored. Here, we show that motor rotation is governed not only by viscosity but also by the supramolecular organisation of the surrounding medium. Thermodynamic analysis reveals that, beyond the viscosity-related increase observed in the isotropic phase of the same host, nematic order introduces an additional enthalpic penalty of 10-14 kJ mol^-1 for the rate-determining thermal helix inversion. The magnitude of this penalty follows the alignment of the metastable cis-states involved in helix inversion, consistent with an order-dependent elastic resistance. These findings identify supramolecular order as a kinetic control parameter for artificial molecular motors and reveal reciprocal coupling between molecular-machine operation and soft-matter organization.