Structural characterisation, BFDH morphology, DSC, infrared and Raman studies of the disordered tetramethylammonium nonachlorodibismuthate [(CH3)4N]3Bi2Cl9

Abstract

The present paper reports on synthesis method, X-ray diffraction, DSC, Infrared and Raman spectroscopy studies carried out on [(CH3)4N]3Bi2Cl9. The structure of this hybrid material is refined by the Reitveld method in the space group P63/mmc (Z = 2), with unit cell parameters: a = 9.2581(2) Å, c = 21.9223(6) Å, V = 1627(1)Å3. It consists from isolated Bi2Cl93- dimer anions composed of two distorted octahedra BiCl63- sharing three chlorine atoms’ face, and three disordered cations (CH3)4N+, forming an organic–inorganic network. There are two disordered cations types: one cation totally disordered with N(1) atom placed in special Wyckoff positions (2b) of (-6m2) site symmetry, and Carbon atoms C1 and C2 are three-fold disordered; the two others cations N(2) observed on special positions (4f) of site symmetry (3 m) are partially disordered, with C4 atom is three-fold disordered and C3 atom is ordered. The BFDH crystal morphology predicted from the Laue symmetry (6/mmm) gives hight faces characterized by two <h k l> faces indices, with their center-to-plane distance dhkl and their growth rates. The simulated model from the space group symmetry (P63/mmc) gives three < h k l > faces indices, which highlights the screw axis 63 and the glide plane c effects in reducing the Importance morphology. The DSC analysis showed that the compound undergoes a reversible phase transition at 74 °C/69 °C (heating/cooling). The Infrared-Raman spectra are studied based by developing theoretical vibrations modes of cations and anions in the crystal; the study confirms the presence of (CH3)4N+ cations and Bi2Cl93- anions, which are linked by CH….Cl hydrogen bonding types.