Solid-State Dynamics and High-Pressure Studies of a Supramolecular Spiral Gear |
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Authors: | Dr Luca Fornasari Dr Anna Olejniczak Dr Federica Rossi Dr Simone d'Agostino Prof Michele R Chierotti Prof Roberto Gobetto Prof Andrzej Katrusiak Prof Dario Braga |
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Institution: | 1. Dipartimento di Chimica G. Ciamician, Università di Bologna, Via Selmi, 2, 40126 Bologna, Italy;2. Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland;3. Department of Chemistry and NIS Centre, University of Torino, Via Giuria 7, 10125 Torino, Italy |
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Abstract: | 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-diazabicyclo2.2.2]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. |
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Keywords: | crystals dynamic processes non-ambient crystallography solid-state NMR spectroscopy |
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