LiSr2SiO4H, an Air-Stable Hydride as Host for Eu(II) Luminescence.

LiSr2SiO4H is synthesized by solid-state reaction of LiH and α-Sr2SiO4. It crystallizes in space group P21/ m ( a = 658.63(4) pm, b = 542.36(3) pm, c = 695.01(4) pm, β = 112.5637(9)°) as proven by X-ray and neutron diffraction, is isotypic to LiSr2SiO4F, and exhibits isolated SiO4 tetrahedra. Hydride anions are located in Li2Sr4 octahedra, which share faces to form columns, with H-H distances of 271.18(2) pm. NMR, IR, and Raman spectroscopy, density measurements, elemental analysis, and theoretical calculations confirm these results. Despite its hydridic nature, it is stable in air up to 550 K. When doped with europium, it emits bright yellow-green light with an intensity maximum at 560 nm for LiSr1.98Eu0.02SiO4H. Even after treatment in water for several hours, the solid shows luminescence. The broad emission peak is attributed to the allowed 4f65d → 4f7 transition of divalent europium. LiSr2SiO4H is the first silicate hydride, a class of compounds that might have potential as host for luminescent materials.