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

• Published in: Chemistry : a European journal Vol. 26; no. 22; pp. 5061 - 5069
• Main Authors: Fornasari, Luca, Olejniczak, Anna, Rossi, Federica, d'Agostino, Simone, Chierotti, Michele R., Gobetto, Roberto, Katrusiak, Andrzej, Braga, Dario
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 16.04.2020
• Subjects: Ambient temperature; Chain dynamics; Chemistry; Crown ethers; crystals; dynamic processes; Dynamic structural analysis; Ethers; Gears; Magnetic resonance spectroscopy; Molecular motion; NMR; NMR spectroscopy; non-ambient crystallography; Nuclear magnetic resonance; Pressure; Pressure effects; Salts; solid-state NMR spectroscopy; non-ambient crystallography; crystals; solid-state NMR spectroscopy; dynamic processes
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201905744

The structures and solid‐state dynamics of the supramolecular salts of the general formula [(12‐crown‐4)2⋅DABCOH2](X)2 (where DABCO=1,4‐diazabicyclo[2.2.2]octane, X=BF4, ClO4) have been investigated as a function of temperature (from 100 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 P3221 and P3121. 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, which mesh and rotate in a concerted manner similar to spiral gears. Above 1.55 GPa, a collapse‐type transition to a lower‐symmetry ordered structure, not attainable at a temperature of 100 K, takes place, proving, thus, that the pressure acts as 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. Supramolecular gears: The solid‐state dynamics of the supramolecular salts of the formula [(12‐crown‐4)2⋅DABCOH2](X)2 (DABCO=1,4‐diazabicyclo[2.2.2]octane, X=BF4, ClO4) have been investigated as a function of temperature and pressure by a combination of non‐ambient XRD techniques and variable‐temperature solid‐state NMR spectroscopy.