New class of Preyssler-lanthanide complexes with modified and extended structures tuned by the lanthanide contraction effect

A family of polyoxometalate compounds based on Preyssler anions and lanthanide cations, K ₅Na ₅[{Pr ₄(H ₂O) ₁₂(pydc) ₄}{Na(H ₂O)P ₅W ₃₀O ₁₁₀}]·46H ₂O (1, H ₂pydc = pyridine-2,6-dicarboxylic acid), Na ₇[{Pr ₄(H ₂O) ₂₀(pydc) ₂(Ac)}{Na(H ₂O)P ₅W ₃₀O ₁₁₀}]·23H ₂O (2), and Na ₁₀H ₂ [{Ln ₂(H ₂O) ₁₀(pydc) ₂}{Na(H ₂O)P ₅W ₃₀O ₁₁₀}]·XH ₂O (Ln = Sm 3, Eu 4, Gd 5; X = 11 for 3 and 5, 13 for 4), have been synthesized and characterized by elemental analysis and single crystal X-ray diffraction. Compound 1 exhibits a two-dimensional honeycomb layer which is built up from unique {Pr ₄} metallacycles and Preyssler anions. Remarkably, the strong involvement of the sodium countercations leads to the formation of a unique three-dimensional open architecture with one-dimensional channels. The 2D grid layer of compound 2 is constructed by the longest currently known rare-earth metal clusters {Pr ₈} and Preyssler anions. Isostructural compounds 3, 4, and 5, obtained by introduction of the intermediate lanthanide ions into the above reaction system, exhibit bisupporting [{Ln ₂(H ₂O) ₁₀(pydc) ₂}{Na(H ₂O)P ₅W ₃₀O ₁₁₀}] ^12- polyoxometalate cluster structures. The magnetic properties of compounds 1 and 2 and the luminescent properties of compounds 3 and 4 are discussed in this paper.