Investigation of a new organic/inorganic hybrid crystal tri(p-chloro-anilium) pentabromocadmate(II) by in situPXRD and FTIR methods: Thermal stability and the route to suppress its decomposition

Abstract

A new organic/inorganic hybrid crystal tri(p-chloro-anilium) pentabromocadmate(II) ((p-Cl-C₆H₄-NH₃)₃CdBr₅) was grown by a programmed cooling method, and its structure was determined using an X-ray diffraction method. This hybrid crystal crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 15.033(2) Å, b = 8.0189(12) Å, c = 23.103(4) Å, β = 99.649(8)°, V = 2745.6(7) ų, Z = 4, R[F² > 2σ(F²)] = 0.0538, wR(F²) = 0.0833. The heating processes of the hybrid crystals were investigated by TGA-DTA, in situ X-ray diffraction (XRD) and Fourier transform infrared (FTIR) measurements. The results revealed that the crystal decomposed in two stages. First, p-chlorobenzenamine hydrobromide (p-Cl-C₆H₄-NH₂HBr) was produced from the crystal when subjected to temperatures above 170 °C, the gas products of p-Cl-C₆H₄-NH₂HBr then followed as the temperature increased continuously. Furthermore, the in situ FTIR spectra collected at high pressure demonstrated that its dissociation temperature increased by ∼22 °C in a nitrogen atmosphere of 4.0 MPa.