Effects of Rotational Symmetry Order on the Solid State Dynamics of Phenylene and Diamantane Rotators

摘要

The potential of controlling rotary dynamics at the molecular level has been recognized by several authors. In that context, we have been interested in structures that emulate macroscopic gyroscopes while in the rigid environment of their crystalline solids. Up to now, these have been constructed with phenylene rotators linked by dialkynyl axles to bulky triarylmethanes (trityls) or triptycenes. Using solid state H NMR, we have shown that the rotary dynamics depend primarily on steric shielding. While structures with simple triptycyls are static, molecular gyroscopes with trityl groups display 180° rotation with rates of ca. 500 Hz at 300 K, and compounds with terf-butyl-substituted trityl frames reach rates that are > 100 MHz at the same temperature (Figure 1).