Novel Sandwiched Intermetallic Selenoantimonates: Soft Synthesis and Characterization of Cu₂SbSe₃·0.5en and Cu₂SbSe₃·en †

Two novel two-dimensional (layered) intermetallic copper selenoantimonates Cu_2SbSe3·O.5en (I) and Cu₂SbSe₃·en (II), have been prepared by soft solvothermal reactions of CuCl, SbCl₃, and Se with A₂Se (A = Na, K) in the presence of ethylenediamine. Single-crystal X-ray diffraction analyses show that both structures crystallize in the monoclinic crystal system. Compound I belongs to the P2₁/n (no. 14) space group with a = 6.399(1) Å, b = 18.858(4) Å, c = 6.786(1) Å, β = 113.23(3)°, Z = 4, V = 752.5(2) ų, and II belongs to the Pn (no. 7) space group with a = 6.321(2) Å, b = 11.841(2) Å, c = 6.932(2) Å, β = 111.59(2)°, Z = 2, V = 482.4(2) ų. Both compounds consist of Cu₂SbSe₃ layers separated by free ethylenediamine molecules. The intermetallic layers are very similar in I and II, but the orientations of the solvent molecules are different. Both compounds contain copper atoms of mixed-valence, Cu(I) and Cu(II), and both are semiconductors with intermediate band gaps (∼1.6 eV).