Heterometallic Clusters [CuSn3S9]5− and [Cu6Sn6S20]10−: Solvothermal Synthesis and Characterization of 4f–3d Thiostannates

Two types of 4f–3d thiostannates with general formula Hen]₂Ln(en)₄(CuSn₃S₉)] ? 0.5 en ( Ln1 ; Ln=La, 1 ; Ce, 2 ) and Hen]₄Ln(en)₄]₂Cu₆Sn₆S₂₀] ? 3 en ( Ln2 ; Ln=Nd, 3 ; Gd, 4 ; Er, 5 ) were prepared by reactions of Ln₂O₃, Cu, Sn, and S in ethylenediamine (en) under solvothermal conditions between 160 and 190 °C. However, reactions performed in the range from 120 to 140 °C resulted in crystallization of Sn₂S₆]^4? compounds and CuS powder. In 1 and 2 , three SnS₄ tetrahedra and one CuS₃ triangle are joined by sharing sulfur atoms to form a novel CuSn₃S₉]^5? cluster that coordinates to the Ln³⁺ ion of Ln(en)₄]³⁺ (Ln=La, Ce) as a monodentate ligand. The CuSn₃S₉]^5? unit is the first thio‐based heterometallic adamantane‐like cluster coordinating to a lanthanide center. In 3 – 5 , six SnS₄ tetrahedra and six CuS₃ triangles are connected by sharing common sulfur atoms to form the ternary Cu₆Sn₆S₂₀]^10? cluster, in which a Cu₆ core is enclosed by two Sn₃S₁₀ fragments. The topological structure of the novel Cu₆ core can be regarded as two Cu₄ tetrahedra joined by a common edge. The Ln³⁺ ions in Ln1 and Ln2 are in nine‐ and eightfold coordination, respectively, which leads to the formation of the CuSn₃S₉]^5? and Cu₆Sn₆S₂₀]^10? clusters under identical synthetic conditions. The syntheses of Ln1 and Ln2 show the influence of the lanthanide contraction on the quaternary Ln/Cu/Sn/S system in ethylenediamine. Compounds 1 – 5 exhibit bandgaps in the range of 2.09–2.48 eV depending on the two different types of clusters in the compounds. Compounds 1 , 3 , and 4 lost their organic components in the temperature range of 110–350 °C by multistep processes.