Li₂Eu₃Br₂[BO₃]₂: A New Europium(II) Halide Oxoborate with Yellow Luminescence

Abstract

The europium(II) oxoborate Li2Eu3Br2[BO3]2 featuring lithium and bromide ions was synthesized by the reaction of Eu2O3 with Li[BH4] as lithium‐ and boron‐ as well as EuBr3 as bromide‐source at 750 °C for 24 h in silica‐jacketed sealed niobium capsules. The yellow, air‐stable and yellow fluorescent compound crystallizes in the trigonal space group R3m (a = 1049.06(7) pm, c = 2993.1(3) pm, c/a = 2.853, Z = 12). The two crystallographically distinguishable Eu2+ cations show either an eightfold coordination as bicapped trigonal prism ([EuO6Br2]12–) or a ninefold coordination as monocapped square antiprism ([EuO5Br4]12–). All oxygen atoms stem from isolated triangular [BO3]3– anions and the Li+ cations reside in octahedral voids provided by both oxygen atoms and Br– anions.