Synthesis of divalent europium borate via in situ reductive techniques

A new divalent europium borate, Eu[B₈O₁₁(OH) ₄], was synthesized by two different in situ reductive methodologies starting with a trivalent europium starting material in a molten boric acid flux. The two in situ reductive techniques employed were the use of HI as a source of H₂ gas and the use of a Zn amalgam as a reductive, reactive surface. While both of these are known reductive techniques, the title compound was synthesized in both air and water which demonstrates that strict anaerobic conditions need not be employed in conjunction with these reductive methodologies. Herein, we report on the structure, spectroscopy, and synthetic methodologies relevant to Eu[B₈O₁₁(OH)₄]. We also report on a europium doping study of the isostructural compound Sr[B ₈O₁₁(OH)₄] where the amount of doped Eu ²⁺ ranges from 2.5 to 11%.