Synthesis and crystal structures of four new bromo-chalcogenides: MnSbS2Br, MnBiSe2Br and two allotropic forms of MnSbSe2Br. Crystal chemistry of the MnPnQ(2)X family (Pn = Sb, Bi ; Q = S, Se ; X = Cl, Br, I)

International audienceFour new compounds, MnSbS2Br,MnBiSe2Br and two allotropic forms of MnSbSe2Br, were synthesized by solid state reaction at 500–600 ◦C. Their crystal structures were determined by single crystal X-ray diffraction. MnSbS2Br, isotypic with MnSbSe2I, is monoclinic, space group C2/m (No 12), with unit cell parameters a = 12.669(3), b = 3.8509(8), c = 9.585(2) Å, β = 91.00(3)◦, V = 467.54(3) Å3, Z = 4, R = 0.0622. MnBiSe2Br and one form of MnSbSe2Br, isotypic with MnSbS2Cl, are orthorhombic, space group Pnma (No 62), with unit cell parameters a = 9.995(2)/10.005(2), b = 4.0275(8)/3.9720(8), c = 12.928(3)/12.871(3) Å, V = 520.44(3)/511.46(18) Å3, Z = 4, R = 0.0421/0.0523, respectively. MnSbSe2Br presents a second allotropic form, orthorhombic, space group Pbam (No 55), with a = 10.046(2), b = 25.994(5), c = 3.9689(8) Å, V = 1036.4(1) Å3, Z = 4, R = 0.0545. This last structure is a 1:1 combination of the two previous types. The crystal chemistry of the MnPnQ2X family is discussed, and its structural types compared with similar (FeUS3) or homologous derivatives (pavonite series)