Aqua Complexes of Rare Earth Metals (Ce3+, Eu3+, Gd3+, and Yb3+) with closo-Dodecaborate Anion: Synthesis, Structure, and Properties

Aqua complexes M(H2O)82B12H123·15H2O (M = Eu3+, Gd3+, Yb3+) and Ce(H2O)92B12H123·15H2O stabilized by the closo-dodecaborate anion have been synthesized by neutralization of an (H3O)2B12H12 solution with rare earth (RE) oxides M2O3 (M = Eu3+, Gd3+, Yb3+) and CeO2. The structures of Eu(H2O)82B12H123·15H2O and Ce(H2O)92B12H123·15H2O have been determined by single-crystal X-ray diffraction analysis. It has been demonstrated that the reaction in the СеО2/(H3O)2B12H12 system is accompanied by the redox transformation Ce4+ → Ce3+, while for the M2O3 (M = Eu3+, Gd3+, Yb3+)/(H3O)2B12H12 systems, the oxidation state of the corresponding RE cation remains unchanged. Studying the luminescent properties of Ce(H2O)92B12H123·15H2O has shown that this compound emits in the near ultraviolet region with an emission maximum at 370 nm.