X-ray diffraction, vibrational properties, and dielectric studies of 3-ammoniumpropyl imidazolium pentabromoantimonate (III)

Abstract

A new organic–inorganic material 3-ammoniumpropyl imidazolium pentabromoantimonate (III) was reported. The title compound was synthesized at room temperature by slow evaporation and then characterized by single-crystal and powder X-ray diffraction, spectroscopic measurements, thermal analysis, and dielectric technique. It crystallizes in the non-centrosymmetric space group P2₁2₁2₁ with the following unit cell parameters: a = 8.7120(7), b = 12.6608(1), c = 14.3498(1) Å with Z = 4. The crystal is built up of separated SbBr₅ ²⁻ polyhedra anions and 3-ammoniumpropyl imidazolium cations. The cohesion of the structure is ensured by network of N–H…Br hydrogen bonds between the 3-ammoniumpropyl imidazolium cations and [SbBr₅]²⁻ anions, in which they may be effective in the stabilization of the crystal structure. The Raman and infrared spectra confirm the presence of both cationic [C₆H₁₃N₃]²⁺ and anionic [SbBr₅]²⁻ entities. Dielectric data were analyzed using complex permittivity ε* and complex electrical modulus M* for the sample at various temperatures. The conductivity follows the Arrhenius low. The Z′ and Zʺ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination of bulk resistance Rp and constant phase elements CPE. [C₆H₁₃N₃]SbBr₅ crystals undergo one endothermic peak at 333 K. This transition was detected by DSC and by dielectric measurements using the impedance and modulus spectroscopy techniques.