X-Ray diffraction and NMR studies on the crystal structures of MABB and MABA at room temperature

Abstract We have investigated the structures of (CH3NH3)3Bi2Br9 (MABB) and (CH3 NH3)3Sb2Br9 (MABA) crystals by X-ray Fourier method and high resolution 15N-NMR in their prototypic phases. A doublet with intensity ratio 2:1 was observed in the NMR spectrum of MABB. The methyl ammonium cations also showed different electron density distributions at two non-equivalent sites. The distribution was examined in connection with splitting of the Br atoms and the NMR results.