Orange -red-emitting Sr5(BO3)3H:Eu2+: The first representative of a new compound class.

The unprecedented borate hydride Sr 5 (BO 3 ) 3 H and Sr 5 (BO 3 ) 3 D crystallizing in an apatite-related structure iare reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu 2+ , it shows broad-band orange-red emission under UV excitation due to the 4f 6 5d-4f 7 transition of Eu 2+ . A number of characterization methods, including 1 H solid-state MAS NMR and vibrational spectroscopy together with quantum chemical calculations of the 1 H chemical shifts and vibrational spectra as well as X-ray and neutron powder diffraction, elemental analysis and luminescence spectroscopy of an Eu 2+ -doped sample were applied to study the compound. The observed 1 H chemical shift is in good agreement with previously reported 1 H chemical shifts of ionic metal hydrides as well as with quantum chemical calculations and very different from 1 H chemical shifts usually found for hydroxide ions in similar materials. FT-IR and Raman spectroscopy of different samples containing 1 H, 2 H, nat B and 11 B combined with calculations unambiguously prove the absence of hydroxide ions and the sole incorporation of hydride ions into the borate. The orange-red emission obtained via doping with Eu 2+ shows that the new compound class might be a promising host material for optical applications.