Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr 5 (BO 3 ) 3 H and Sr 5 ( 11 BO 3 ) 3 D.

The unprecedented borate hydride Sr ₅ (BO ₃ ) ₃ H and deuteride Sr ₅ ( ¹¹ BO ₃ ) 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 Eu ²⁺ , it shows broad-band orange-red emission under violet excitation owing to the 4f ⁶ 5d-4f ⁷ transition of Eu ²⁺ . 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 Eu ²⁺ shows that the new compound class might be a promising host material for optical applications.
(© 2020 The Authors. Published by Wiley-VCH GmbH.)