Synthesis,Structure and Bonding,Optical Properties of Ba4MTrQ6 (M=Cu,Ag; Tr=Ga,In; Q=S,Se)

Four new quaternary chalcogenides, Ba₄AgGaS₆ ( 1 ), Ba₄AgGaSe₆ ( 2 ), Ba₄CuInS₆ ( 3 ), and Ba₄AgInS₆ ( 4 ), were synthesized by solid‐state reactions and their structures were characterized through single‐crystal X‐ray diffraction. In spite of their similar chemical compositions, the flexible arrangement between the transition metals and the triel atoms leads to subtle differences in their polyanion structures. All structures feature similar MTrQ₆]^8? 1D polyanionic chains (M=Cu, Ag; Tr=Ga, In; Q=S, Se), which are constructed from corner‐sharing MQ₄ or TrQ₄ tetrahedra. However, the transition metals and triels are mixed in 1 , 2 , and 3 , but they occupy independent crystallographic sites in 4 . As a result, compounds 1 – 3 belong to the known Ba₂CoS₃ (Pnma No. 62) or Ba₂MnS₃ (Pnma No. 62) class, whereas 4 crystallizes in its own structural type within the monoclinic P2₁/c (No. 14) space group. The structural relationship among these new phases was also studied with the aid of DFT calculations and related optical properties are presented as well.