Isostructural phase transition in m-carboxyphenylammonium monohydrogenphosphite

Abstract

Crystals of m-carboxyphenylammonium monohydrogenphosphite, C7H8NO2+.H2PO3- (m-CPAMP), space group P2(1)/c, grown from aqueous solution undergo a reversible first-order single-crystal phase transition at Tc = 246 (2) K with a hysteresis of 3.6 K. The thermal behaviour of the sample was characterized by differential scanning calorimetry (DSC) experiments. Variations of the unit-cell parameters versus temperature between 100 and 320 K are reported. The transition from the higher-temperature phase (HTP) to the lower-temperature phase (LTP) is characterized by a unit-cell volume contraction of 1.77%. The average structure and unit-cell packing of m-CPAMP at lower temperature (100 K) are reported from accurate X-ray data sets and compared with those of the higher-temperature phase (293 K) in order to investigate the mechanism of the phase transition. The reciprocal lattice reconstruction showed a few very weak satellite reflections which will be discussed in a forthcoming paper.

Thermal, Spectroscopic, and Ab Initio Structural Characterization of Carprofen Polymorphs

“…Polymorphic transformations that do not imply a dramatic change of the unit cell parameters and the crystal symmetry but are only associated with topographically different (or differently oriented) H bonds and different intermolecular interactions induced by variations of torsion angles, although uncommon, are known in literature. 39,40 Polymorphism should, however, in such cases be assessed with particular caution, especially when polymorphic studies are conducted in nonambient conditions. Unusual anisotropic thermal expansions of the cell parameters have been, in fact, observed in situ as a function of temperature, which were intricate to clearly distinguish from isostructural conformational polymorphism.…”

Polymorphism and Solvatomorphism 2005

“…The 2005 literature also contained a number of additional reports that summarized investigations of the phase transitions among polymorphs and solvatomorphs of various organic compounds, and the thrust of these159–166 have been summarized in Table 3.…”

Following an isosymmetric phase transition by changes in bond lengths and anisotropic displacement parameters: the case of meta-carboxyphenylammonium phosphite

“…1 On the basis of the temperature evolution of the unit-cell parameters, this isosymmetric phase transition was shown to be reversible and first-order with a hysteresis of 3.6 K (see Fig. 4 of Bendeif et al, 2005). Although the phase transition induces a significant reorganization of the molecular packing (see Figs.…”

“…Recently, we have reported on an original isosymmetric single-crystal phase transition at 246 (2) K in a new phosphite salt (m-carboxyphenylammonium monohydrogenphosphite, m-CPAMP, C 7 H 8 NO þ 2 , HPO 3 H À ; Bendeif et al, 2005). 1 On the basis of the temperature evolution of the unit-cell parameters, this isosymmetric phase transition was shown to be reversible and first-order with a hysteresis of 3.6 K (see Fig.…”