Solvothermal syntheses, structures and properties of quaternary alkaline earth metal sulfides BaCu6Ge2S8 and BaCuAsS3.

Two quaternary alkaline earth metal sulfides, BaCu 6 Ge 2 S 8 (1) and BaCuAsS 3 (2), were synthesized under low-temperature solvothermal conditions. Compound 1 features a three-dimensional (3D) [Cu 6 Ge 2 S 8 ] n 2n- framework comprising CuS 3 , CuS 4 , and GeS 4 units, with Ba2+ cations occupying the channels. Compound 2 exhibits a one-dimensional (1D) chained structure, with Ba2+ cations situated between the chains. Alkaline earth metal ions exhibit a structural directing effect that is distinct from that of other guest cations. Specifically, Compound 1 presents a rare instance of a 3D Cu-Ge-S framework formed by condensation of two parallel layers. Compound 2 is the first 1D A-Cu-As-S compound (where A represents guest cations). Additionally, compound 2 presents the first example of AⅡ-Cu-As-S (where AⅡ represents alkaline earth metal cations) compounds. Their optical properties and theoretical calculations were also investigated. Our results demonstrate that solvothermal synthesis is a promising method for obtaining multinary alkaline earth metal sulfides with diverse structures and properties. [Display omitted] • Two quarternary alkaline earth metal sulfides were prepared using the low-temperature solvothermal method. • The solvothermal method reduces the synthesis temperature and is beneficial for obtaining thermodynamic metastable phases. • Compound 2 presents the first example of AⅡ-Cu-As-S (AⅡ = alkaline earth metal cations). [ABSTRACT FROM AUTHOR]