Synthesis, Structure, and Spectroscopic Properties of the New Lanthanum(III) Fluoride Oxomolybdate(VI) La 3 FMo 4 O 16

La 3 FMo 4 O 16 crystallizes in the triclinic crystal system with space group P $\bar {1}$ [ a = 724.86(2) pm, b = 742.26(2) pm, c = 1469.59(3) pm, α = 101.683(2)°, β = 102.118(2)°, γ = 100.279(2)°] with two formula units per unit cell. The three crystallographically independent La 3+ cations show a coordination number of nine each, with one F – and eight O 2– anions forming distorted monocapped square antiprisms. The fluoride anion is coordinated by all three lanthanum cations to form a nearly planar triangle. Besides three crystallographically independent tetrahedral [MoO 4 ] 2– units, a fourth one with a higher coordination number (CN = 4 +1) can be found in the crystal structure, forming a dimeric entity with a formula of [Mo 2 O 8 ] 4– consisting of two edge‐connected square pyramids. Several spectroscopic measurements were performed on the title compound, such as infrared, Raman, and diffuse reflectance spectroscopy. Furthermore, La 3 FMo 4 O 16 was investigated for its capacity to work as host material for doping with luminescent active cations, such as Ce 3+ or Pr 3+ . Therefore, luminescence spectroscopic as well as EPR measurements were performed with doped samples of the title compound. Both the pure and the doped compounds can be synthesized by fusing La 2 O 3 , LaF 3 and MoO 3 (ratio 4:1:12; ca. 1 % CeF 3 and PrF 3 as dopant, respectively) in evacuated silica ampoules at 850 °C for 7 d.