Syntheses, structures, and properties of sulfides constructed by SbS4 teeter-totter polyhedra: Ba3La4Ga2Sb2S15 and BaLa3GaSb2S10

Two new pentanary sulfides Ba3La4Ga2Sb2S15 (1) and BaLa3GaSb2S10 (2) have been discovered by high temperature solid state reactions. Ba3La4Ga2Sb2S15 features a new zero-dimensional structure type, which consists of unique isolated Sb2S7 dimers and GaS4 tetrahedra. In contrast, with less GaS4 tetrahedra in the formula, BaLa3GaSb2S10 forms a one-dimensional structure which is constructed by teeter-totter (SbS4)n chains and isolated GaS4 tetrahedra. On the basis of UV/Vis spectroscopy, their band gaps are determined to be 2.42 and 2.15 eV, respectively, which are much wider than that of analogue La4FeSb2S10 (1.0 eV). In addition, theoretical studies illustrate the important role of Ga in expanding the band gaps with respect to Fe atoms. The calculated crystal orbital Hamilton population and electron localization function confirm that the long Sb–S bonds in Ba3La4Ga2Sb2S15 (2.932(2) Å) and BaLa3GaSb2S10 (3.216(5) and 3.219(5) Å) have weak but nonnegligible bonding interactions.