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

Abstract

The structures and solid-state dynamics of the supramolecular salts of the generalf ormula [(12-crown-4) 2 ·DABCOH 2 ](X) 2 (whereD ABCO = 1,4-diazabicyclo[2.2.2]octane, X = BF 4 ,C lO 4 )h ave been investigated as af unction 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.T he two salts are isomorphous and crystallize in the enantiomeric space groups P3 2 2 1 and P3 1 2 1 .A ll 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) thankst ot he correlation between neighboring molecules, whichm esh and rotate in ac oncerted manner similar to spiralg ears. Above 1.55 GPa, ac ollapse-type transition to al ower-symmetry ordered structure, not attainable at at emperature 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.[a] Dr.

Compression and Thermal Expansion in Organic and Metal–Organic Crystals: The Pressure–Temperature Correspondence Rule

“…Alterations in temperature and pressure can affect the molecular aggregation in crystals and lead to solid-state phase transitions or chemical reactions, − and formation of different polymorphs − or pseudopolymorphs. − Moreover, the pressure or temperature changes can cause visible macroscopic effects in the color and shape of the crystal − and thermosalient behavior, − or can alter the molecular motions in crystalline molecular machines. − Although pressure and temperature can lead to the same kinds of phenomena (phase transitions, shape changes, etc. ), it is natural to expect that response can differ, both qualitatively and quantitatively.…”

Stepwise Stress‐Induced Transformations of Metal‐Organic Polyhedral Cluster‐Based Assemblies: Where Conformational and Supramolecular Features Meet

“…Our groups have a long‐standing interest in the elucidation of factors controlling self‐organization processes of metal complexes, [33,39,43] the design and construction of porous molecular crystals, [27,33,40,41,44] the investigation on dynamics of supramolecular networks, [45–48] and the search for new polymorphs [49–51] . Based on these experiences, we purposefully selected a polyhedral zinc‐oxo cluster incorporating monoanionic N , N’ ‐diphenylformamidinate ( dipf ) ligands, [(μ 4 −O)Zn 4 ( dipf ) 6 ] ( 1 ).…”

Engineering plastic phase transitions via solid solutions: the case of “reordering frustration” in ionic plastic crystals of hydroxyquinuclidinium salts

“…13 C CPMAS spectra were acquired at a spinning speed of 12 kHz, using a ramp cross-polarization pulse sequence with a 90°1H pulse of 3.60 μs, contact time of 3 ms, optimized recycle delays between 0.5 and 8 s, number of scans in the range 150-800, depending on the sample. 15 N CPMAS spectra were acquired at a spinning speed of 9 kHz using a ramp cross-polarization pulse sequence with a 90°1H pulse of 3.60 μs, contact time of 4 ms, optimized recycle delays between 0.5 and 8 s, number of scans in the range 8000-10000, depending on the sample. 31 P CPMAS spectra were acquired at a spinning speed of 12 kHz using a ramp cross-polarization pulse sequence with a 90°1H pulse of 3.60 μs, contact time of 4 ms, optimized recycle delay of 0.6 s and 200 scans.…”

“…To this end, we synthesized a series of [QH]X salts with various counter-anions, including the tetrahedral anions sulfate (SO 4 ), see Scheme 2, by the metathesis of [QH]Cl using metal salts of the corresponding anions. A combination of solid-state techniques, including variable temperature XRD, thermal analyses, multinuclear ( 11 B, 13 C, 15 N, 19 F and 31 P) solid-state NMR spectroscopy, variable temperature wideline 19 F T 1 relaxation measurements and micro-Raman spectroscopy, was used to elucidate crystal structures and phase transition behavior of the so-obtained materials.…”