Lanthanide–tungstobismuthate clusters based on [BiW9O33]9− building units: synthesis, crystal structures, luminescent and magnetic properties

Abstract

The reaction of Na₁₂[Bi₂W₂₂O₇₄(OH)₂]·44H₂O, Na₉[BiW₉O₃₃]·16H₂O, lanthanide chloride and Na₂CO₃ in aqueous solution at a pH value of about 7.0 resulted in the three unprecedented giant lanthanide–tungstobismuthate clusters Na_xH_22−x[(BiW₉O₃₃)₄(WO₃){Bi₆(μ₃-O)₄(μ₂-OH)₃}(Ln₃(H₂O)₆CO₃)]·nH₂O {Ln = Pr³⁺ (1), Nd³⁺ (2), La³⁺ (3), x = 22 (1), 22 (2), 20 (3), n = 95 (1), 91 (2), 73 (3)}. These three complexes represent the first examples of lanthanide ions encapsulated in polyoxotungstobismuthates and the largest polytungstobismuthates so far. Furthermore, a [{Bi₆(μ₃-O)₄(μ₂-OH)₃}]⁷⁺ polyoxo cation was incorporated into the structure of these compounds. All complexes are characterized by single-crystal X-ray diffraction, IR spectra, electronic spectroscopy, thermogravimetric and elemental analysis. Magnetic investigation revealed that the progressive depopulation of excited Stark sublevels of the lanthanide ions at low temperature and the weak antiferromagnetic interaction between the neighboring metal centres are responsible for the magnetic properties of 1 and 2. The original synthesis strategy in this work may open a gateway to assembly of large lanthanide–tungstobismuthates clusters and novel multifunctional solid materials in aqueous solution under mild conditions.