Chloride Derivatives of Lanthanide Ortho‐Oxomolybdates: 1. Structural Comparison, Magnetic Properties, and Luminescence of the LnCl[MoO4] Representatives with the Smaller Lanthanides (Ln = Sm–Lu)

Abstract

AbstractThe lanthanide chloride ortho‐oxomolybdates LnCl[MoO4] (Ln = Sm–Yb) crystallize in the monoclinic space group C2/m (a = 1035–1010 pm, b = 736–713 pm, c = 691–678 pm, β = 106.7–107.4°, Z = 4), while LuCl[MoO4] displays a triclinic structure (space group P, a = 591.42(2) pm, b = 716.19(3) pm, c = 681.44(3) pm, α = 93.724(2)°, β = 102.463°, γ = 122.134(2)°, Z = 2). The isotypical monoclinic derivatives exhibit one crystallographically unique site for the lanthanide cations with a coordination number of eight (2 × Cl– and 6 × O2– arranged as trigonal dodecahedra). The Lu3+ cations in LuCl[MoO4] also occupy a single crystallographic position, but with a coordination number of only seven (2 × Cl– and 5 × O2–, arranged as monocapped trigonal prisms). The coordination polyhedra around the lanthanide cations in the LnCl[MoO4] representatives (Ln = Sm–Yb) are connected to each other via three common edges, building up a ∞2{[LnCl2/2eO4/2eO2/1t]6–} layer parallel to the ab plane. These layers are cross‐linked along [001] by Mo6+ cations, which on their part form tetrahedral ortho‐oxomolybdate units [MoO4]2–. In LuCl[MoO4] only two edges of the [LuCl2O5] polyhedra are interconnected, constituting a ∞1{[LuCl2/2eO2/2eO3/1t]6–} chain along [100]. These chains arrange as a sheered primitive rod‐packing with the Mo6+ cations connecting these strands to each other, again by the formation of tetrahedral [MoO4]2– entities. Magnetic measurements were performed for GdCl[MoO4] and DyCl[MoO4], exhibiting Curie‐Weiss behaviour for both compounds. Luminescence and excitation spectra of EuCl[MoO4] and TbCl[MoO4] were measured. Under UV excitation both bulk materials show intense red and green luminescence, respectively. This is slightly uncommon, since most bulk compounds do not show intense luminescence due to concentration quenching.