Ferroelasticity and piezoelectricity of organic–inorganic hybrid materials with a one-dimensional anionic structure: so similar, yet so different

The synthesis, structural aspects, thermal and dielectric analysis for new members of the ferroic family, polynuclear Bi( iii ) and Sb( iii ) halide complexes based on a pyrazolium cation with the formulas (C 3 N 2 H 5 )[BiCl 4 ]·H 2 O and (C 3 N 2 H 5 )[SbCl 4 ]·H 2 O, are presented. The former compound was found to undergo a ferroic phase transition of the ferroelastic type at 213/219 K (cooling/heating scans), whereas, the latter one exhibited a piezoelectric feature in the dielectric response function. The molecular motions of pyrazolium cations were analyzed based on the spin–lattice relaxation time of 1 H NMR measurements.