An ionothermal synthesis study of transition metal phosphates using the ionic liquid 1-butyl-4-methylpyridinium hexafluorophosphate [C4mpy]­[PF6] yielded four new, different open framework manganese compounds, that is, K2Mn3(HPO4)2(PO3F)­F2 (1), (NH4)2Mn3(HPO4)2(PO3F)­F2 (2), KMn3(H2PO4)­(HPO4)2F2 (3), and (NH4)­Mn3(H2PO4)­(PO3F)2F2 (4). The obtained products not only feature new framework topologies unprecedented in the family of phosphates but also interesting properties as the transition metal gives rise to both luminescent (rendering them potential nonrare earth containing red emitting phosphors) and unconventional magnetic properties governed by geometric frustrations. Aside from the structural analysis (powder and single-crystal X-ray diffraction, infrared spectroscopy), a variety of characterization methods (photoluminescence spectroscopy and magnetic measurements) were applied to study the material’s properties. Single crystal X-ray studies reveal that 1 (P21/c with a = 5.501(1), b = 14.203(3), c = 16.905(4) Å, β = 108.65(3)°, V = 1251.4 Å3, and Z = 4) and 2 (P2 1 /c with a = 5.587(1), b = 14.507(3), c = 17.364(3) Å, β = 108.75(3)°, V = 1332.6(5) Å3, and Z = 4) feature S-shaped 18-ring channels along [100], which are formed by trimer-Mn3O9F2 chains parallel to [100] and interconnecting PO3(OH) and PO3F tetrahedra. The structure of compounds 3 (C2/c with a = 20.307(4), b = 7.635(1), c = 7.834(2) Å, β = 103.26(3)°, V = 1182.2(4) Å3, and Z = 4) and 4 (C2/c with a = 20.402(4), b = 7.673(1), c = 7.845(2) Å, β = 103.56(3)°, V = 1193.8(4) Å3, and Z = 4) are characterized by layers, which are built of Mn3O8F4 octahedra trimers, with Kagomé topology parallel to the bc plane featuring 3,6-ring channels. The layers are stacked according to a sequence of AA i along the a axis. Taking into account the [P(2)­O3(OH)/P­(2)­O3F] tetrahedra, the Kagomé layers are replenished to a Mn3O2(HPO4)/Mn3O2(PO3F) composition, which are interlinked by [P(1)­O2(OH)2] forming 10-ring channels parallel to [001]. Charge compensation of the macroanions is achieved by K+ (1 and 3) and (NH4)+ (2 and 4) cations. At room temperature, compounds 1–4 demonstrate a reddish orange emission ascribed to the spin-forbidden 4T1g(4G) → 6A1g(6S) transition of the Mn2+ ions. Upon lowering the temperature to 77 K, the emission of each compound is red-shifted and becomes pure red. Compounds 1 and 2 contain spin trimers with a presumable doubled ground state. The intertrimer magnetic coupling is relatively weak, and small ferrimagnetic domains are possible in 1. The magnetic behavior of 3 and 4 can be considered as antiferromagnetic. This can be understood as their staircase Kagomé lattices are distorted, meaning that the intrinsic geometrical frustration is lifted.

Abstract. The lanthanide(III) chloride oxidotungstates(VI) with the formula Ln 3 Cl 3 [WO 6 ] for Ln = La -Nd, Sm -Tb were synthesized by solid-state reactions utilizing the respective lanthanide trichloride, lanthanide sesquioxide (where available), and tungsten trioxide together with lithium chloride as flux. The title compounds crystallize hexagonally in space group P6 3 /m (no. 176, a = 941-909, c = 543-525 pm, Z = 2). The structures comprise crystallographically unique Ln 3+ cations surrounded by six O 2-and four Cl -anions (C.N. = 10) forming distorted tetracapped trigonal prisms as well as rather uncommon trigonal prismatic [WO 6 ] 6-units, whose edges are coordinated by

Pale yellow crystals of LnSb2O4Br (Ln = Eu–Tb) were synthesized via high temperature solid-state reactions from antimony sesquioxide, the respective lanthanoid sesquioxides and tribromides. Single-crystal X-ray diffraction studies revealed a layered structure in the monoclinic space group P21/c. In contrast to hitherto reported quaternary lanthanoid(III) halide oxoantimonates(III), in LnSb2O4Br the lanthanoid(III) cations are exclusively coordinated by oxygen atoms in the form of square hemiprisms. These [LnO8]13− polyhedra form layers parallel to (100) by sharing common edges. All antimony(III) cations are coordinated by three oxygen atoms forming ψ1-tetrahedral [SbO3]3− units, which have oxygen atoms in common building up meandering strands along [001] according to {[SbO2/2vO1/1t]–}∞1 (v = vertex-sharing, t = terminal). The bromide anions are located between two layers of these parallel running oxoantimonate(III) strands and have no bonding contacts with the Ln3+ cations. Since Sb3+ is known to be an efficient sensitizer for Ln3+ emission, photoluminescence studies were carried out to characterize the optical properties and assess their suitability as light phosphors. Indeed, for both, GdSb2O4Br and TbSb2O4Br doped with about 1.0–1.5 at-% Eu3+ efficient sensitization of the Eu3+ emission could be detected. For TbSb2O4Br, in addition, a remarkably high energy transfer from Tb3+ to Eu3+ could be detected that leads to a substantially increased Eu3+ emission intensity, rendering it an efficient red light emitting material.

The lanthanide(III) chloride oxidomolybdates-(VI) with the empirical formula Ln 3 Cl 3 [MoO 6 ] (Ln = La, Pr, and Nd) were synthesized by solid-state reactions utilizing the respective lanthanide trichloride, lanthanide sesquioxide (where available), and molybdenum trioxide together with lithium chloride as a fluxing agent. The title compounds crystallize in hexagonal space group P6 3 /m (a = 942−926 pm, c = 542−533 pm, Z = 2). Besides tetracapped trigonal prismatically coordinated Ln 3+ cations, noncondensed trigonal prismatic [MoO 6 ] 6− entities are found in the crystal structure. In addition to X-ray diffraction, the title compounds were also characterized by single-crystal Raman and infrared spectroscopy as well as measurements to determine their magnetic susceptibility and behavior at low temperatures. The most outstanding properties of the Ln 3 Cl 3 [MoO 6 ] representatives (Ln = La, Pr, and Nd), however, are of an optical nature, because their band gaps, determined by diffuse reflectance spectroscopy, show a significant shift toward lower energies compared to those of other rare-earth metal chloride molybdates with a different polyhedral arrangement. This culminates in La 3 Cl 3 [MoO 6 ]:Eu 3+ exhibiting luminescence, which can be excited in the visible range of the electromagnetic spectrum by a blue light-emitting diode.