Comment on “1,4-Diazabicyclo[2.2.2]octane-based disalts showing non-centrosymmetric structures and phase transition behaviors” by X.-B. Han, P. Hu, C. Shi and W. Zhang, CrystEngComm, 2016,18, 1563

Abstract

This Letter is in response to a paper by Han et al. (CrystEngComm, 2016, 18, 1563–1569) on the structures and isostructural phase transitions in (dabcoH2)(BF4)2·H2O and (dabcoH2)(ClO4)2·H2O. It is shown that the phase transitions in these compounds have a second-order character and their low-temperature phases exhibit ferroelastic properties. Thus, the transitions cannot be isostructural. The redeterminations of both crystal structures as a function of temperature evidence that at the transition points the symmetry is reduced from orthorhombic to triclinic.