Synthesis and Structures of the New Group IV Chalcogenides NaCuTiS₃ and NaCuZrQ₃ (Q = S, Se, Te)

The new compounds NaCuTiS₃ and NaCuZrQ₃ (Q = S, Se, Te) have been synthesized through reaction of the elements with a Na₂Q_n flux. The compounds NaCuTiS₃, NaCuZrSe₃, and NaCuZrTe₃ crystallize in space group D¹⁶_2h-Pnma of the orthorhombic system with four formula units in cells of dimensions a = 12.738(10), b = 3.554(3), c = 9.529(8) Å for NaCuTiS₃; a = 13.392(5), b = 3,833(1), c = 10.250(4) Å for NaCuZrSe₃; a = 14.34(4), b = 4.06(1), c = 10.93(3) Å for NaCuZrTe₃ (T = 113 K). NaCuZrS₃ crystallizes in space group D¹⁷_2h -Cmcm of the orthorhombic system with four formula units in a cell of dimensions a = 3.688(1), b = 12.838(5), c = 9.726(3) Å. The structures of all four compounds have been determined by single-crystal X-ray methods. The structures are composed of ²_∞[CuMQ^-₃] (M = Ti, Q = S; M = Zr, Q = S, Se, Te) layers separated by Na⁺ cations. The Cu atoms are tetrahedrally coordinated and the M atoms are octahedrally coordinated. NaCuZrS₃ is isostructural with the recently reported series of compounds KCuZrQ₃ (Q = S, Se, Te). NaCuTiS₃, NaCuZrSe₃, and NaCuZrTe₃ represent a new structure type with the ²_∞ [CuMQ^-₃] layer being composed of alternating pairs of CuQ₄ tetrahedra and MQ₆ octahedra in the [001] direction. The Na¹ cations are coordinated by seven chalcogen atoms in a monocapped trigonal prismatic arrangement.