Solid‐State Dynamics and High‐Pressure Studies of a Supramolecular Spiral Gear.

The structures and solid-state dynamics of the supramolecular salts of general formula [(12-crown-4) 2 DABCOH 2 ](X) 2 (where X=BF 4 , ClO 4 ) have been investigated as a function of temperature (from 100 K to 360 K) and pressure (up to 3.4 GPa), through the combination of variable temperature and variable pressure XRD techniques and variable temperature solid-state NMR spectroscopy. The two salts are isomorphous and crystallize in the enantiomeric space groups P3 2 2 1 and P3 1 2 1 . All building blocks composing the supramolecular complex display dynamic processes at ambient temperature and pressure. It has been demonstrated that the motion of the crown ethers is maintained on lowering the temperature (down to 100 K) or on increasing the pressure (up to 1.5 GPa) thanks to the correlation between neighboring molecules that mesh and rotate in a concerted manner similarly to spiral gears. Above 1.55 GPa, a collapse-type transition to a lower-symmetry ordered structure, not attainable at a temperature of 100K, takes place, proving, thus, that the pressure acts like the means to couple and decouple the gears. The relationship between temperature and pressure effects on molecular motion in the solid state has also been discussed.