Crystal Structure and Phase Transitions of [C(NH2)3]3l3Sb2Cl9· 0.9 H2O

Abstract

Abstract The room temperature structure of [C(NH2)3]3Sb2Cl9 · 0.9 H2O (GNCA) was solved. It crystal­ lizes in the monoclinic C2/c space group with a = 15.275, b = 8.794, c = 17.904 (in Å), β = 96.40°, V = 2390 Å3, Z = 4. Refinement of the atomic parameters by a least squares methods gave R = 0.042, wR = 0.039 for 1958 reflections with F>4σ(F). The structure consists of polyanionic (Sb2Cl9 3-)n layers built of deformed corner connected SbX6 3-octahedra. Two crystallographically inequivalent guanidinium cations are present, one situated between polyanionic layers, the other one together with a disordered water molecule inside cavities formed by polyanions. Temperature X-ray scattering experiments together with DSC studies were carried out above room temperature. Temperature dependence of the lattice parameters between 300 K and 380 K was determined and a phase transition of mixed order at 364 K was revealed.