Crystal structure, spectroscopic properties, and magnetic behavior of the fluoride-derivatized lanthanoid(III) ortho-oxomolybdates(VI) LnF[MoO4] (Ln=Sm–Tm)

The fluoride-derivatized lanthanoid(III) ortho-oxomolybdates(VI) LnF[MoO4] (Ln=Sm–Tm) crystallize in the monoclinic space group P21/c with four formula units per unit cell (a=516–528 pm, b=1220–1248 pm, c=659–678 pm, β=112.5–113.1°). The structure contains one crystallographically unique Ln3+ cation surrounded by two fluoride and six oxide anions in a square antiprism (CN=8). The square antiprisms [LnF2O6] are interconnected via three edges to form layers ∞2{[LnF2/2eO4/2eO2/1t]6-} parallel (010), which are cross-linked along [010] by Mo6+ in tetrahedral oxygen coordination to form the three-dimensional crystal structure. The fluoride anions within this arrangement exhibit a twofold coordination of Ln3+ cations in the shape of a boomerang, which is connected to another F− anion to form planar [F2Ln2]4+ rhombuses. Magnetic measurements for GdF[MoO4], TbF[MoO4], and DyF[MoO4] show Curie–Weiss behavior, despite the peculiar arrangement of the lanthanoid(III) cations in layers comparable with those of gray arsenic. Furthermore, Raman, infrared, and diffuse reflectance spectroscopy data for these compounds were recorded and interpreted.

Graphical abstractView at the crystal structure of LnF[MoO4] (Ln=Sm–Tm) along [100] with special emphasis on the isolated [MoO4]2− tetrahedra (blue) and the [F2Ln2]4+ rhombuses (green).Figure optionsDownload full-size imageDownload as PowerPoint slide