Synthesis and crystal structures of four new bromo-chalcogenides: MnSbS2Br, MnBiSe2Br and two allotropic forms of MnSbSe2Br. Crystal chemistry of the MnPnQ2XMnPnQ2X family (Pn=SbPn=Sb, Bi; Q=SQ=S, Se; X=ClX=Cl, Br, I)

Four 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/mC2/m (No 12), with unit cell parameters a=12.669(3)a=12.669(3), b=3.8509(8)b=3.8509(8), c=9.585(2) Åc=9.585(2) Å, β=91.00(3)°β=91.00(3)°, V=467.54(3) Å3V=467.54(3) Å3, Z=4Z=4, R=0.0622R=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)a=9.995(2)/10.005(2), b=4.0275(8)/3.9720(8)b=4.0275(8)/3.9720(8), c=12.928(3)/12.871(3) Åc=12.928(3)/12.871(3) Å, V=520.44(3)/511.46(18) Å3V=520.44(3)/511.46(18) Å3, Z=4Z=4, R=0.0421/0.0523R=0.0421/0.0523, respectively. MnSbSe2Br presents a second allotropic form, orthorhombic, space group Pbam   (No 55), with a=10.046(2)a=10.046(2), b=25.994(5)b=25.994(5), c=3.9689(8) Åc=3.9689(8) Å, V=1036.4(1) Å3V=1036.4(1) Å3, Z=4Z=4, R=0.0545R=0.0545. This last structure is a 1:1 combination of the two previous types. The crystal chemistry of the MnPnQ2XPnQ2X family is discussed, and its structural types compared with similar (FeUS3) or homologous derivatives (pavonite series).

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