La₂CuS₄: A Lanthanum Copper Sulfide with Discrete Anion Triples [S₃Cu⋅⋅⋅SS⋅⋅⋅CuS₃]¹²⁻ Based on La₄[Cu₂S₆(S₂)]

Abstract

Some unusual material properties of solid-state compounds are due to the special coordination geometry of the ions in the crystal structure. For example, the superconductivity of YBa 2 Cu 3 O 7Àd (04 j d j 41) [1] is, in part, the result of the valence of the copper ions being greater than + ii and their coordination by oxygen atoms in many different ways: Certain Cu + cations are surrounded by O atoms in a squarepyramidal arrangement, whereas others adopt an almost square-planar (for d = 0) or linear coordination geometry (for d = 1). The properties of these rare-earth copper oxides change when oxygen is substituted by other chalcogens such as sulfur. Thus, studies of rare-earth/copper/sulfur systems should provide results on new ternary or quaternary rareearth copper chalcogenides. Mainly those substances that exhibit both unusual oxidation states and coordination geo-

Combined computational and experimental investigation of the La 2 CuO 4– x S x (0 ≤ x ≤ 4) quaternary system

“…2 28 and La 3 CuO 2 S 329 appear, and when x=4, LaCuS 2 and La 2 CuS 430 phases dominate. Except for these overall observations, side-by-side comparisons of the reactions have also revealed several interesting aspects of this system.…”

Synthesis, Crystal and Electronic Structure of La2SiP4

“…La 2 SiP 4 crystallizes in the La 2 CuS 4 structure type; [30] however, unlike Cu in the sulfide, Si atoms in the crystal structure of La 2 SiP 4 are tetrahedrally coordinated with four P atoms. The distances in SiP 4 tetrahedra vary in the 2.191–2.232 Å range, which is in good agreement with other ternary metal silicon phosphides [12,21,31–33] .…”

“…The La 2 SiP 4 crystal structure is related to the structure of La 2 CuS 4 ternary metal sulfide (Figure 4). [30] La 2 CuS 4 crystallizes in the same space group ( P 2 1 / c ), but is characterized by discrete anion triplets [S 3 Cu−S−S−CuS 3 ] 12− , where slightly out‐of‐plane [CuS 3 ] 5− triangles are bridged by disulfide anions [S 2 ] 2− . La 3+ cations are surrounded by bicapped trigonal prims of sulfur.…”

“…Here we report the newest member of the 2‐1‐4 family, La 2 SiP 4 , crystallizing in the monoclinic P 2 1 / c space group. This structure is related to the ternary sulfide, La 2 CuS 4 ; [30] however unlike the latter, which has isolated CuS 3 triangles bridged by disulfide ions, the phosphide has SiP 4 tetrahedra connected via P−P bonds forming 1D zig‐zag chains along the [001] direction.…”

Syntheses, Structure, Magnetism, and Optical Properties of the Ordered Interlanthanide Copper Chalcogenides Ln2YbCuQ5 (Ln = La, Ce, Pr, Nd, Sm; Q = S, Se): Evidence for Unusual Magnetic Ordering in Sm2YbCuS5

“…Rare-earth copper chalcogenides have been the source of considerable interest, not only because of their diverse structures and electronic properties, but also because of some unusual coordination geometries and oxidation states of copper that they exhibit. − The large number of rare-earth copper chalcogenides can be divided into two groups, based on different interactions between chalcogenides. In the Group 1 phases, there are no Q−Q (Q = S, Se, Te) interactions.…”