Synthesis, crystal and electronic structure of the quaternary sulfides Ln2CuMS5 (Ln=La, Ce; M=Sb, Bi)

•Ln2CuSbS5 are complex quarternary phases crystallizing in their own structure type.•Ln2CuSbS5 and Ce2CuBiS5 are new compound in the respective ternary phase diagrams.•Ln2CuSbS5 on one side, and Ln2CuBiS5 on the other are not isotypic.

The series of quaternary sulfides with general formula Ln2CuMS5 (Ln=La, Ce; M=Sb, Bi) have been synthesized by solid-state reactions. Three representative members have been structurally characterized by single-crystal X-ray diffraction. La2CuSbS5 crystallizes in a new structure type (space group Ima2 (no. 46), Z=4, a=13.401(2) Å, b=7.592(1) Å, c=7.598(1) Å, V=773.1(3) Å3). The bismuth analogs of composition La2CuBiS5 and Ce2CuBiS5 crystallize with the La2CuInSe5 structure type (space group Pnma (no. 62), Z=4). Lattice parameters for La2CuBiS5: a=11.9213(5) Å, b=3.9967(2) Å, c=17.0537(8) Å, V=812.56(7) Å3; lattice parameters for Ce2CuBiS5: a=11.9179(15) Å, b=3.9596(5) Å, c=16.955(2) Å, V=800.13(17) Å3). The similarities and the differences between the two structures are discussed. Electronic structure calculations for La2CuSbS5 and La2CuBiS5 are also presented; they suggest semiconducting behavior with energy gaps exceeding 1.7 eV.

Graphical abstractLa2CuSbS5 crystallizes in a new structure type (space group Ima2 (no. 46). Its bismuth analog La2CuBiS5 crystallizes in the La2CuInSe5 structure type (space group Pnma (no. 62)). Z=4, a=11.9213(5) Å, b=3.9967(2) Å, c=17.0536(10) Å, V=813.53(10) Å3). The structures are based on rare-earth metal atoms coordinated by S atoms in a trigonal-prismatic and/or square-antiprismatic fashion, Cu-centered tetrahedra, and pnictogen atoms in pyramidal or distorted octahedral coordination.Figure optionsDownload full-size imageDownload as PowerPoint slide