Abstract
The scandium oxodiselenate(IV) Sc2[Se2O5]3 was synthesized via solid-state reactions between scandium sesquioxide (Sc2O3) and selenium dioxide (SeO2) with thallium(I) chloride (TlCl) as fluxing agent in molar ratios of 1:4:2. Evacuated fused silica ampoules were used as reactions vessels for annealing the mixtures for five days at 800 °C. The new scandium compound crystallizes in the triclinic space group P 1 ¯ with the lattice parameters a = 663.71(5) pm, b = 1024.32(7) pm, c = 1057.49(8) pm, α = 81.034(2)°, β = 87.468(2)°, γ = 89.237(2)° and Z = 2. There are two distinct Sc3+ positions, which show six-fold coordination by oxygen atoms as [ScO6]9− octahedra (d(Sc–O) = 205–212 pm). Three different [Se2O5]2− anions provide these oxygen atoms with their terminal ligands (Ot). Each of the six selenium(IV) central atoms exhibit a stereochemically active lone pair of electrons, so that all [Se2O5]2− anions consist of two ψ1-tetrahedral [SeO3]2− subunits (d(Se–Ot) = 164–167 pm, d(Se–Ob) = 176–185 pm, ∢(O–Se–O) = 93–104°) sharing one bridging oxygen atom (Ob) with ∢(Se–Ob–Se) = 121–128°. The vibrational modes of the complex anionic [Se2O5]2− entities were characterized via single-crystal Raman spectroscopy.
Highlights
Owing to their potential as materials with an inorganic antenna effect [1] within energy transfer processes for lighting applications, many rare-earth metal(III) oxoselenates(IV) were published with different structural characteristics in the past decades
A numerical absorption correction was carried out with the program HABITUS [26], but the structure solution and refinement was performed with the program SHELX-97 [27,28]
Three different complex anionic [Se2 O5 ]2− groups occur in the crystal structure (Figure 3), showing different dihedral angles between the two (O,O,O)-faces ((O1,O2,O3)–(O3,O4,O5) = 121.2◦ ; (O6,O7,O8)–(O8,O9,O10) = 146.0◦ ; (O11,O12,O13)–(O13,O14,O15) = 152.2◦ )
Summary
Owing to their potential as materials with an inorganic antenna effect [1] within energy transfer processes for lighting applications, many rare-earth metal(III) oxoselenates(IV) were published with different structural characteristics in the past decades. Oxoselenates(IV) with the simple formula RE2 [SeO3 ]3 (≡ RE2 Se3 O9 ; RE = Sc, Y, La–Lu) [2,3,4,5,6,7,8,9,10,11,12] show a cornucopia of structure and space-group types. The RE2 [SeO3 ]3 -type phases with lanthanum and cerium show an orthorhombic structure in space-group Pnma [2,4]. All further rare-earth metals(III) (RE = Y, Sm–Lu) [6,7,10] adopt the same triclinic crystal structure for their
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