Synthesis, crystal structures and spectroscopic properties of pure YSb(2)O(4)Br and YSb(2)O(4)Cl as well as Eu(3+)- and Tb(3+)-doped samples

The quaternary halide-containing yttrium(iii) oxidoantimonates(iii) YSb(2)O(4)Cl and YSb(2)O(4)Br were synthesised through solid-state reactions from the binary components (Y(2)O(3), Sb(2)O(3) and YX(3), X = Cl and Br) at 750 °C in evacuated fused silica ampoules with eutectic mixtures of NaX and CsX (X = Cl and Br) as fluxing agents. YSb(2)O(4)Cl crystallizes tetragonally in the non-centrosymmetric space group P42(1)2 with unit-cell parameters of a = 773.56(4) pm and c = 878.91(6) pm, whereas YSb(2)O(4)Br is monoclinic (space group: P2(1)/c) with a = 896.54(6) pm, b = 780.23(5) pm, c = 779.61(5) pm and β = 91.398(3)°, both for Z = 4. The two new YSb(2)O(4)X compounds contain [YO(8)](13−) polyhedra, which are connected via four common edges to form [Image: see text] layers (d(Y(3+)–O(2−)) = 225–254 pm) without any Y(3+)⋯X(−) bonds (d(Y(3+)⋯X(−)) > 400 pm). Moreover, all oxygen atoms belong to ψ(1)-tetrahedral [SbO(3)](3−) units, which are either connected to four-membered rings [Sb(4)O(8)](4−) in the chloride (Y(2)[Sb(4)O(8)]Cl(2) for Z = 2) or endless chains in the bromide (Y(1/2)(SbO(2))Br(1/2) for Z = 8) by common vertices. With distances of 307 pm in YSb(2)O(4)Cl and 326 pm in YSb(2)O(4)Br there are not even substantial bonding Sb(3+)⋯X(−) (X = Cl and Br) interactions at work. Luminescence spectroscopy on samples doped with trivalent europium and terbium showed an energy transfer from the oxidoantimonate(iii) moieties as the sensitizer in the host structure onto the lanthanoid activators.