In an early step towards emulating the dynamics of rotary biomolecular nanomachines, we report here the design and dynamics of a crystalline molecular rotor with a relatively large triptycene rotator. With cross-section and surface area that are two and three times larger than those of the phenylene rotators previously studied in the solid state, it was expected that van der Waals forces and steric hindrance would render the motion of the larger triptycene more difficult. To address this challenge, we used a molecular design that consists of a rigid, shape-persistent, shielding stator in a dendritic structure that reaches ca. 3.6 nm in length. Using variable temperature solid state 2H NMR we determined a symmetric three-fold rotational potential with a barrier of 10.2 kcal/mol and a pre-exponential factor of 1.1x1010 s-1, which correspond to ca. 4600 Brownian jumps per second at ambient temperature (300 K) in the solid state.

Rotation of a bulky triptycene in the solid state: Towards engineered nanoscale artificial molecular machines

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.