Temperature-induced reversible structural phase transition of 1,4-dimethyl-1,4-diazabicyclo[2.2.2]octane bis(perchlorate)

Abstract

octane bis(perchlorate), C 8 H 18 N 2 2+ ·2ClO 4 − , was synthesized. Differential scanning calorimetry (DSC) measurement detected that this compound underwent a reversible phase transition at ca. 201.7 K, which was also confirmed by dielectric measurements.The single crystal X-ray diffraction data suggests that the phase transition undergoes from a room temperature paraelectric phase with a space group of Pnma to a low temperature paraelectric one with a space group of P2 1 /n. The order-disorder transition of ClO 4 − anions and the ordering of twisting motions of dabco ring may drive the phase transition.

Switchable Dielectric Materials Based on a Diprotonated Organic Cation Containing Two Different Anions: (C5H16N2)BF4X (X = Cl, Br, NO3)

“…The N value is greater than 2, indicating that the compounds underwent order–disorder phase transition rather than displacement phase transition when stimulated by temperature. Notably, the phase transition temperature of 1 , 2 , and 3 is higher than that of most similar compounds previously reported. − …”

“…1H, 19F, 11B, and 13 C NMR spectra of all compounds were acquired in dimethyl sulfoxide on a Bruker AV NEO 600 MHz spectrometer with the BBFO probe. The frequency of 1 H, 19 F, 11 B, and 13 C is 600.13, 564.69, 192.55, and 150.90 MHz, respectively. Infrared spectra were recorded on a Bruker INVENIO R instrument with a resolution of 4 cm −1 ; the scanning time is 32 scans, and the range of the wave number is 4000− 400 cm −1 .…”

“…The successive reports of such molecular-based compounds with attractive properties (e.g., ferroelectricity and dielectricity) have prompted researchers to turn their attention to similar compounds with diprotonated organic cations. − For example, the switchable phase transition behavior of compounds based on protonated divalent organic cations such as (1-chlormethyl-dabco)­(ClO 4 ) 2 and (CH 3 -dabco-CH 3 )­(ClO 4 ) 2 has been proved to be related to the order–disordered dynamic change of the compounds. The reported charge-balanced of diprotonated organic cationic compounds mainly focus on the use of the same anion (such as ClO 4 − , BF 4 − , Br − , I − ), few use different anions to balance the charge of diprotonated organic cationic to construct stimulus-responsive materials, especially for molecular-based phase change materials.…”

Crystal structure, magnetism, and dielectric properties based on the axially chiral ligand 2,2′-dinitro-4,4′-biphenyldicarboxylic acid

“…The dielectric behaviors of MOFs, which are mostly caused by polarization, can be attributed to the hydrogen-bond interaction of polar guest molecules inside host frameworks and the order-disorder orientation arrangement or displacement and shift caused by atom vibration in crystal lattices. [53][54][55][56][57][58][59][60][61][62][63][64] The complex dielectric behavior ε (ε = ε′ − iε″, where ε′ and ε″ are the corresponding real part and imaginary part, respectively) is dependent on the temperature and electric field at various frequencies. 65 Herein we explored the dielectric properties of six MOFs 1-6 at 125-300 K and 500 Hz to 1 MHz based on pellets from their powdered samples due to the difficulty in obtaining enough large single crystals.…”

Four solid forms of tauroursodeoxycholic acid and solid-state transformations: effects of temperature and milling

“…Recently, solid-state transformation induced by various solvent-free technologies, as environmental-friendly methods to acquire relevant solid forms, including temperature-triggered transformation, 34,40,41 milling, 42,43 thermo-mechanical technology, 31 extrusion, 44 and pressure-induced transformation, 45 has rapidly developed and is attracting increasing attention from researchers. High-temperature-induced solid-state transformation has been reported in several pharmaceuticals.…”