Monolacunary Keggin polyoxometalates connected to ten 4d or 4f metal atoms

Abstract

The rational self-assembly of mono-lacunary Keggin clusters with 4d and 4f metal salts via a conventional method has yielded two novel polyoxometalate-based 4d–4f heterometallic compounds containing lacunary Keggin anions connected to ten metal atoms: {[Ag{Ag₂(H₂O)₄}{Ln(H₂O)₆}₂H ⊂ {SiW₁₁Ln(H₂O)₄O₃₉}₂]·nH₂O (Ln = Ce and n = 7 for 1, Ln = Pr and n = 3 for 2). Their structures were determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. A structural feature in 1 and 2 is that each [SiW₁₁O₃₉]⁸⁻ cluster (SiW₁₁) is connected to ten metals (five Ag⁺ and five Ln³⁺ cations), representing the highest number of connected metal atoms to any mono-lacunary Keggin anion to date. This large connectivity leads to a structure with a purely inorganic 3D framework with two kinds of channels along the [100] and [010] directions. The magnetic properties of both compounds show the expected magnetic moments (0.8 and 1.6 amu K mol⁻¹ per Ce³⁺ and Pr³⁺ ion, respectively) and confirm the presence of isolated Ce³⁺ and Pr³⁺ ions.