Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs₂NaLn(PS₄)₂ (Ln = La–Nd, Sm, and Gd–Ho)

Abstract

The effect of lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations were obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs2NaLn­(PS4)2 (Ln = La–Nd, Sm, and Gd–Ho) were grown as large single crystals (∼0.1–1 mm3) and characterized using single-crystal X-ray diffraction and magnetic susceptibility measurements. As we moved across the series, the structural studies revealed a change in the lanthanide coordination environment depending on the identity of the lanthanide. Although all compounds in the Cs2NaLn­(PS4)2 series crystallize in the same space group and have the same Wyckoff atom positions, a slight change in size between Sm3+ and Gd3+ causes a subtle change in coordination number from 9 (for Ln = La–Sm) to 8 (for Ln = Gd–Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Magnetic measurements performed on the Cs2NaLn­(PS4)2 (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

Synthesis of Hydrated Ternary Lanthanide-Containing Chlorides Exhibiting X-ray Scintillation and Luminescence

“…In this study, we observed that on moving across the lanthanide series (Eu–Lu), the symmetry of the compounds changes and the coordination number of the lanthanide cations decreases from 9 to 8, as a consequence of lanthanide contraction, resulting in six different compositions. By comparison, this effect was observed by Klepov et al where a minor change in size between the lanthanide cations causes a sharp change in the coordination environment and coordination number, resulting in different structure types . The lanthanide chloride compounds, although having different symmetries and compositions, all consist of lanthanide polyhedra that are isolated from each other but linked into a complex structure by Cs–Cl/Cs–O bonds and by extensive OH–O hydrogen bonding and OH–Cl interactions.…”

“…By comparison, this effect was observed by Klepov et al where a minor change in size between the lanthanide cations causes a sharp change in the coordination environment and coordination number, resulting in different structure types. 43 The lanthanide chloride compounds, although having different symmetries and compositions, all consist of lanthanide polyhedra that are isolated from each other but linked 5)°f orming a distorted square antiprism (Figure 2a). The Cs1− Cs2, Cl1−Cl7, and O1−O6 are located at positions of general crystallographic symmetry (Wyckoff site 8d), whereas Cs3− Cs8, Cl8−Cl10, and O7−O9 are located on or are disordered across (O9) mirror planes (Figure S3).…”

Li3La[PS4]2: The First Lithium Lanthanum Ortho‐Thiophosphate

“…The new lithium-containing lanthanum(III) ortho-thiophosphate(V) Li 3 La[PS 4 ] 2 crystallizes orthorhombically in the space group Pbca (no. 61) displaying the lattice parameters a = 1053.51(6) pm, b = 1920.62 (11) pm and c = 1165.83 (7) pm with Z = 8 (Table 1). There is only one crystallographically unique lanthanum position, three lithium, two phosphorus and eight sulfur sites, all located on the general Wyckoff position 8c, within the crystal structure of Li 3 La[PS 4 ] 2 (Table 2).…”

“…Alkali-metal containing lanthanoid(III) ortho-thiophosphates(V) occur with a rich variety of compositions, for example K 9 Ce-[PS 4 ] 4 , [1] K 3 Ce[PS 4 ] 2 , [2] K 6 Yb 3 [PS 4 ] 5 , [3] K 3 Nd 3 [PS 4 ] 4 , [4] Rb 3 Sm[PS 4 ] 2 , [5] Rb 3 Pr 3 [PS 4 ] 4 , [6] Cs 3 Sm[PS 4 ] 2 , [5] Cs 3 Nd[PS 4 ] 2 , [4] Cs 3 La 5 [PS 4 ] 6 [7] and Cs 3 Pr 5 [PS 4 ] 6 , [8] especially when the heavy representatives potassium, rubidium and cesium are considered. In their crystal structures the discrete [PS 4 ] 3À tetrahedra do not only provide coordination spheres with mostly eight sulfur atoms to the central Ln 3 + cations, as it is also the case for the ternary Ln[PS 4 ] phases (Ln = LaÀ Yb [9,10,11,12] except for Lu [13] with C.N.…”

“…Here the small Li + cations settle in four-to sixfold coordination of sulfur atoms. Owing to topological peculiarities, such as Li + -cation disorder and high anisotropic displacement parameters, they all should be suitable candidates for lithiumion conductors, as has already been proven for other sulfurbased lithium compounds, e. g. Li 3 [PS 4 ], [22] Li 4 [P 2 S 6 ], [23] Li 7 [PS 4 ][P 2 S 7 ] [24] or the lithium argyrodites Li 7 S 2 [PS 4 ], [25] Li 7À x S 2À x Cl x [PS 4 ] and Li 6 SCl-[PS 4 ], [23] to name just some thiophosphate examples. With extra cations like those of the alkali metals (A = LiÀ Cs) the three-dimensional framework of the Ln[PS 4 ] representatives (Ln = LaÀ Lu) becomes less cross-linked and structures with reduced dimensionalities emerge.…”