Solvothermal (Hydrothermal) Synthesis Of Main-Group Elemental Chalcogenides

Studies on syntheses and structures of chalcogenides are of increasing interest because of their unique physical and chemical properties which are promising for applications in semiconductors, photoconductivity, non-linear optics, catalysis and ion exchange. This work focuses on the synthesis and characterization of some main-group elemental chalcogenides by using solvothermal or hydrothermal technique through selecting suitable solvent and templating agents. We aim to develop new chalcogenides with novel stuctures.Using ethylenediamine as a structure-directing agent in the mixture organic solvent, we have synthesized a new compound (EnH2)2Ge2S6 and crystal structure was determined by single crystal X-ray diffraction method. Structure analysis indicates that it crystallizes in a monoclinic system, space group P21/n with a=6.7125(5)A, b=11.2290(4) A, c=10.7518(4) A, α=90°, β=92.288(2)°, γ=90°.The compound comprises of isolated diborane-like Ge2S64-formed by edge-sharing of two tetrahedral GeS4. It is further characterized by EDS, IR, DSC-TG, powder XRD, the results indicate that the compound is stable below 200 °C and a semiconductor with an estimated bad gap of 3.9 eV.Using tetramethylammonium as a structure-directing agent, hydrothermal technique was used for the synthesis of double chain compound [(CH3)4N]As3S5 and crystal structure was determined by single crystal X-ray diffraction method. Structure analysis indicates that it crystallizes in triclinic, space group P1, a =9.554(3)A, b =10.4874(18) A, c =14.027(2) A, α=91.873(15)°, β=91.879(19) °, γ=92.86(2)°. The polymeric anion of [(CH3)4N]As3S5 consists of adjacent 1∞[AS3S5]- chains linked together into a 1∞ [As6S10]2- double chains through planar As2S2 rings . A relatively undistorted Ψ-AsS4 trigonal bipyramidal geometry is observed for the participating As atoms.Furthermore, we have discussed the synthetic factors affecting the crystallization of chalcogenides, such as solvent, structure-directing agent, temperature and pH value etc, and further summarized some synthetic regularities in synthesizing chalcogenides, which will be helpful for the design and synthesis of new chalcogenides.