Wydział Chemii

Daria Budzikur-Maciąg

Przemysław Szklarz

Vasyl V. Kinzhybalo

Katarzyna A. Ślepokura

2020

Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials

76

939-947

10.1107/s2052520620011439

Naukowa

Angielski

Artykuł

Two imidazolium hypodiphosphates, (C₃H₅N₂)(H₃P₂O₆) (I) and (C₃H₅N₂)₂(H₂P₂O₆) (II), have been synthesized and structurally characterized. In both metal-free organic–inorganic hybrids (I) and (II), the hypodiphosphate mono- and dianions, (H­₃P₂O₆)⁻ and (H₂P₂O₆)²⁻, form hydrogen-bonded frameworks of different types, to which the organic cations are linked via N—HO and C—HO hydrogen bonds. The purity of the compounds was confirmed by powder X-ray diffraction. Differential scanning calorimetry of compound (I) revealed two structural phase transitions: continuous at 311.8 K [cooling/heating; from high-temperature phase (HTP) to room-temperature phase (RTP)] and a discontinuous one at 287.9/289.2 K [RTP → low-temperature phase (LTP)]. Compound (I) is characterized in a wide temperature range by single-crystal and powder X-ray diffraction methods. Crystal structures of high- and low-temperature phases are determined, which show orthorhombic (HTP, Pnna, No. 52) → monoclinic (LTP, P2₁/n11, No. 14, a-axis doubled) structural change on cooling with an intermediate incommensurately modulated phase (RTP). Dynamic properties of polycrystalline (I) were studied by means of dielectric spectroscopy. The dielectric behaviour is explained by the motion of imidazolium cations.

imidazolium hypodiphosphate, crystal structure, order–disorder phase transition, thermal analysis, dielectric properties, metal-free organic–inorganic hybrid, hypodiphosphate salts, imidazolium salts, hypodi­phospho­ric acid, phase transition

http://dx.doi.org/10.1107/s2052520620011439