Synthese und Kristallstrukturen von Bromid—Thiosilicaten Ln3Br[SiS4]2 der Lanthanide (Ln = La, Ce, Pr, Nd, Sm, Gd)

Abstract

Inhaltsübersicht. Einkristalle der BromidϪThiosilicate Ln 3 Br[SiS 4 ] 2 wurden durch Reaktion von Lanthanidmetall (Ln ϭ La, Ce, Pr, Nd, Sm, Gd), Schwefel, Silicium und elementarem Brom in Quarzglasampullen dargestellt. Die Thiosilicate kristallisieren monoklin in der Raumgruppe C2/c (Z ϭ 4) isotyp zu den IodidϪAnaloga Synthesis and Crystal Structures of Lanthanide Bromide Thiosilicates Ln 3 Br[SiS 4 ] 2 Abstract. Single crystals of the bromideϪthiosilicates Ln 3 Br[SiS 4 ] 2 were prepared by reaction of lanthanide metal (Ln ϭ La, Ce, Pr, Nd, Sm, Gd), sulfur, silicon and bromine in quartz glass tubes. The thiosilicates crystallize in the monoclinic spacegroup C2/c (Z ϭ 4) isotypically to the iodide analogues Ln 3 I[SiS 4 ] 2 and the AϪtype chlorideϪoxosilicates Ln 3 Cl[SiO 4 ] 2 with the following lattice constants: La 3 Br[SiS 4 ] 2 : a ϭ 1583.3(4) pm, b ϭ 783.0(1) pm, c ϭ 1098.2(3) pm, β ϭ 97.33(3)°C e 3 Br[SiS 4 ] 2 : a ϭ 1570.4(3) pm, b ϭ 776.5(2) pm, c ϭ 1092.2(2) pm, β ϭ 97.28(2)°P r 3 Br[SiS 4 ] 2 : a ϭ 1562.6(3) pm, b ϭ 770.1(2) pm, c ϭ 1088.9(2) pm, β ϭ 97.50(2)°E

Controlling the Luminescence of Rare-Earth Chalcogenide Iodides RE3(Ge1–xSix)2S8I (RE = La, Ce, and Pr) and Ce3Si2(S1–ySey)8I

“…The monoclinic crystal structure (La 3 Si 2 O 8 Cl-type, space group C 2/ c ) of these compounds consists of two RE , one Tt , four Ch , and one I site (Figure a). This structure type was known so far for RE 3 Si 2 O 8 Cl, ,, RE 3 Si 2 S 8 X ( X = Cl, Br, and I), − and RE 3 Ge 2 S 8 I, with RE restricted to the early rare-earth metals. Isolated TtCh 4 tetrahedra are arranged in one-dimensional stacks, which are grouped in opposite-pointing pairs aligned along the c -direction.…”

“…Among these compounds, those containing rare-earth ( RE ) metals could exhibit interesting magnetic and optical properties arising from the localized f-electrons of the RE cations, but they remain relatively rare, numbering around 50 . Within the family of quaternary sulfide halides RE 3 Si 2 S 8 X ( RE = early rare-earth metals; X = Cl, Br, and I), the Ce-containing members were first reported to exhibit strong luminescence in the blue region. − Subsequently, La 3 Si 2 S 8 Br was exploited as a host to prepare phosphors that give broad-band emissions in the cyan region when doped with Ce 3+ or in the red-orange region when doped with Eu 2+ , demonstrating promise for applications in phosphor-converted white light-emitting diodes . Luminescent materials based on sulfides provide advantages over oxides because their greater covalency tends to shift the emission wavelengths toward the visible region; thus, SrS, ZnS, and SrGa 2 S 4 are well known to act as hosts in electroluminescent devices. − On the other hand, these sulfides tend to be less stable and require encapsulation.…”

5 Carbon, silicon, germanium, tin and lead

“…75 The chemistry of the [SiS 4 ] 4Ϫ ion as been advanced by the report of the synthesis of KCe 77 Further new examples are given by the series of compounds Ln 3 Br[SiS 4 ] 2 (Ln = La, Ce, Pr, Nd, Sm and Gd) prepared from the elements. 78 Elemental sulfur reacts with Eu 2 Ge to give α-Eu 2 GeS 4 , a compound that has magnetic characteristics (µ = 7.85 µ B /Eu) which indicate that europium is present as Eu(). The compound orders antiferromagnetically with a T N of 5.0 K and, despite the presence of two distinct Eu centres in the crystal structure, the 197 Eu Mössbauer spectrum shows a single signal δ = Ϫ12.4 mm s Ϫ1 at 78 K. 79…”

Samarium chloride sulfide thiosilicate, Sm3ClS2[SiS4]

“…The structures of compounds in the system of lanthanide, sul®de, silicon and halide have been one of our focuses over the last two years. Up to now, the following homologue groups have been published: the lanthanide iodide thiosilicates Ln 3 I[SiS 4 ] 2 (Ln = La±Nd, Sm and Tb) (Gauthier et al, 1998a,b;Hatscher & Urland, 2001, 2002c, the lanthanide bromide thiosilicates Ln 3 Br[SiS 4 ] 2 (Ln = La±Nd, Sm and Gd) (Hatscher & Urland 2002a), and the lanthanide chloride thiosilicates Ln 3 Cl[SiS 4 ] 2 (Ln = La±Pr) (Hatscher & Urland, 2002b), all crystallizing in the monoclinic space group C2/c. These compounds are isotypic with the so called A-type of the lanthanide chloride oxosilicates, ®rst discovered by Gravereau et al (1988).…”