Low dimensional materials: Syntheses, structures, and optical properties of Rb2CuTaS4, Rb2CuTaSe4, RbCu 2TaSe4, K3Ag3Ta2Se 8, and Rb3AgTa2Se12

Article abstract of DOI:10.1515/znb-2004-0910

The new compounds Rb₂CuTaS₄ (1), Rb ₂CuTaSe₄ (2), RbCu₂TaSe₄ (3), K ₃Ag₃Ta₂Se₈ (4), and Rb ₃AgTa₂Se₁₂ (5) have been synthesized by the reactive flux method at 773 or 873 K. Their crystal structures were determined by single crystal X-ray diffraction. Crystal data for 1: space group Fddd, a = 5.598(1), b = 13.512(4), c = 23.854(5) ?, Z = 8; Crystal data for 2: space group Fddd, a = 5.782(1), b = 13.924(3), c = 24.653(5) ?, Z = 8; Crystal data for 3: space group C2cm, a = 5.7218(3), b = 19.2463(13), c = 7.7456(5) ?, Z = 4; Crystal data for 4: space group C2/c, a = 25.1374(19), b = 6.1007(3), c = 14.4030(11) ?, β = 119.703(8), Z = 4; Crystal data for 5: space group P2₁/n, a = 9.8186(6), b = 13.7462(11), c = 15.7368(9) ?, β = 96.681(7)°, Z = 4. The compounds 1 and 2 are built up of _∞¹[CuTaQ₄]^2- anionic chains which are formed by edge-sharing CuQ₄ and TaQ₄ tetrahedra. The rubidium cations are located between the chains. Compound 3 consists of _∞²[Cu₂TaSe₄]^- anionic layers separated by rubidium cations. The anionic layers are formed by _∞¹[CuTaSe₄]^2- chains which are connected by CuSe₄ tetrahedra that share common edges with the TaSe₄ tetrahedra of neighboring chains. In compound 4 _∞¹[Ag₃Ta₂Se₈] ^3- anionic chains are found which are separated by potassium cations. These chains are formed by successive corner sharing of AgSe₄ tetrahedra and edge sharing between AgSe₄ and TaSe₄ tetrahedra. All three structures are closely related with the sulvanite (Cu ₃VS₄) structure type. Compound 5 contains a one dimensional _∞¹[AgTa₂Se₁₂] ^3- anionic chain formed by interconnection of AgSe₄ tetrahedra and [Ta₂Se₁₁] units. In the structure three monoselenide, three diselenide, and one triselenide anions are found. Raman and far-IR spectroscopic data of compounds 1 and 4 were collected and an interpretation is presented.