Synthesis, crystal structure, and optical properties of Ba2SbO2SX (X = Br, I) oxy-chalcohalides

Highlights: • Ba₂SbO₂SX (X = Br, I), which contain stable complex ternary-anionic fragments are reported. • The optical properties are investigated, which are mainly attributed to the S-3p →Sb-5ptransitions. • Ba₂SbO₂SI exhibits an emission peak at 579 nm under 375 nm radiation. -- Abstract: Two isostructural compounds, Ba₂SbO₂SX (X = Br, I), have been successfully synthesized via solid state reaction. Their structures belong to the space group $C_{2h}^2-P21/m$ (No. 11) of the monoclinic system. They feature a quasi-two-dimensional (2D) network of distorted capped trigonal prisms [XBa₇]¹³⁺ along the a-b plane intercalated by [SbSO₂]^3- triangular pyramid. The optical band gaps of Ba₂SbO₂SBr and Ba₂SbO₂SI are 1.93 eV ad 2.03 eV, respectively. Ba₂SbO₂SI also exhibits an emission peak at 579 nm under 375 nm radiation. First-principles calculation reveals that the optical absorptions of Ba₂SbO₂SX are mainly attributed to the S-3p→Sb-5p transitions. The photoluminescence emission of Ba₂SbO₂SI is mainly contributed by the excitation of the states of the Sb−S bonds.