Structural phase transitions in [C₆H₅NH₃]₂SiF₆: differential scanning calorimetry and Raman studies

Abstract

Phenylammonium hexafluorosilicate, [C 6 H 5 NH 3 ] 2 SiF 6 , crystallizes at room temperature in the orthorhombic system with probable space group Pmmm. Two structural phase transitions were detected at 226 and 280 K by means of differential scanning calorimetry and basic thermodynamic data were determined for these transitions. The internal vibrational modes of [C 6 H 5 NH 3 ] 2 SiF 6 were studied at room temperature and through the phase transitions by using Raman spectroscopy. These studies indicate that the vibrational state of the phenyl cations is weakly changed during these two phase transitions.

Order-Disorder Phase Transition, Anisotropic and Switchable Dielectric Constants Induced by Freeze of the Wheel-Like Motion in a Hexafluorosilicate-Based Crystal

“…For example, bis(tris(hydroxymethyl)methylammonium) hexafluorosilicate undergoes a phase transition induced by a freezing of reorientational motion of the hexafluorosilicate anion . And motions of the hexafluorosilicate moiety contribute to the mechanism of the first‐order phase transition at around 280/286 K in phenylammonium hexafluorosilicate . However, to the best of our knowledge, only these two hexafluorosilicate‐drived phase transition materials were reported.…”

Distinct phase transitions and dielectric anomalies in two 4-methylanilinium salts

“…Both compounds belong to a family of organic-inorganic hybrid compounds synthesized from bases and acids, such as aniline and its derivatives with various inorganic acids [12][13][14][15][16][17][18][19][20][21][22]. Differential scanning calorimetry (DSC), temperature-dependent single-crystal X-ray diffraction and dielectric studies reveal interesting structural phase transitions and dielectric anomalies in the two compounds.…”