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Crystal structures and phase transitions of imidazolium hypodiphosphates
Author(s) -
Budzikur Daria,
Szklarz Przemysław,
Kinzhybalo Vasyl,
Ślepokura Katarzyna A.
Publication year - 2020
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520620011439
Subject(s) - monoclinic crystal system , orthorhombic crystal system , differential scanning calorimetry , crystallography , atmospheric temperature range , crystallite , phase (matter) , dielectric , materials science , powder diffraction , phase transition , crystal (programming language) , crystal structure , chemistry , analytical chemistry (journal) , organic chemistry , thermodynamics , physics , optoelectronics , computer science , programming language
Two imidazolium hypodiphosphates, (C 3 H 5 N 2 )(H 3 P 2 O 6 ) (I) and (C 3 H 5 N 2 ) 2 (H 2 P 2 O 6 ) (II), have been synthesized and structurally characterized. In both metal‐free organic–inorganic hybrids (I) and (II), the hypodiphosphate mono‐ and dianions, (H 3 P 2 O 6 ) − and (H 2 P 2 O 6 ) 2− , form hydrogen‐bonded frameworks of different types, to which the organic cations are linked via N—H…O and C—H…O 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, P 2 1 / n 11, 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.