Five New Chalcohalides, Ba3GaS4X (X = Cl, Br), Ba3MSe4Cl (M = Ga, In), and Ba7In2Se6F8: Syntheses, Crystal Structures, and Optical Properties

Five new chalcohalides, Ba3GaS4X (X = Cl, Br), Ba3MSe4Cl (M = Ga, In), and Ba7In2Se6F8, have been synthesized by conventional high-temperature solid-state method. These compounds crystallize in three different interesting structure types. Ba(3)GaQ(4)X (Q= S, X = Cl, Br; Q = Se, X = Cl) contain zigzag BaX pseudolayers and isolated GaQ(4) tetrahedra, while Ba3InSe4Cl possesses one Ba-In-Se pseudolayer and one Ba-Cl pseudolayer, which are stacked alternately along the c-direction. Ba7In2Se6F8 is comprised of one-dimensional (infinity)(1)[InSe3](3-) chains and unique [Ba7F8](6+) chains. In all those mixed anion compounds, the halide anions are only connected to alkaline-earth metal through strong ionic bonding, while the M (M = Ga, In) cations are only connected to chalcogenide anions through covalent bonding. UV-vis-NIR spectroscopy measurements indicate that Ba(3)GaQ(4)X (Q= S, X = Cl, Br; Q= Se, X = Cl) have band gaps of 2.14, 1.80, and 2.05 eV, respectively.