Cucurbituril-likeGiant PolyOxoThiometalate: StructuralAnalysis and Solution Studies

Polycondensation processes of metalate ions in the presence of a dinuclear linker {Mo₂E₂S₂}²⁺ (E = O, S) and weakly chelating ligands such as acetate or sulfate lead to giant polyoxometalate species, assembled through the connection of pentagonal metal-oxo units. While the most popular structural archetype is undoubtedly the Keplerate-type capsule, topologically reminiscent of the fullerene C₆₀, we report here on the formation conditions of a new giant polyoxothiometalate, whose large cylindrical shape resembles that of organic cucurbituril. The [(SO₄)₂₀(H₁₂₀W₈₀Mo₄₀S₄₀O₃₆₀)]^40– anion has been isolated as single crystals suitable for X-ray diffraction analysis, highlighting the large dimensions of the cucurbituril-like assembly, which reaches 24 Å in length and 14 Å in diameter. The solution behavior of this gigantic polyanion was investigated by Raman, UV–vis spectroscopy, and small-angle X-ray scattering, revealing that its structure is maintained in aqueous solution. These overall results open relevant perspectives in the field of supramolecular chemistry.