Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅...

The unprecedented borate hydride Sr₅ (BO₃ )₃ H and deuteride Sr₅ (¹¹ BO₃ )₃ D crystallizing in an apatite-related structure are reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu²⁺ , it shows broad-band orange-red emission under violet excitation owing to the 4f⁶ 5d-4f⁷ transition of Eu²⁺ . The observed ¹ H NMR 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. FTIR 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 by doping with Eu²⁺ shows that the new compound class might be a promising host material for optical applications.