Synthesis, structure, electrochemistry and magnetism of cobalt-, nickel- and zinc-containing [M₄(OH)₃(H₂O)₂(-SiW_{10< /sub>O36.5)2]^13- (M = Co²⁺, Ni²⁺, and Zn²⁺)}

Interaction of the trilacunary 9-tungstosilicate [A-alpha-SiW9O34](10-) with cobalt(ii), nickel(ii) and zinc(ii) ions in pH 9 aqueous medium at room temperature led to the formation of the respective M-4-containing heteropolytungstates [M-4(OH)(3)(H2O)(2)(alpha-SiW10O36.5)(2)](13-) (M = Co2+ (1), Ni2+ (2), and Zn2+ (3)). Polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR spectroscopy, and thermogravimetric and elemental analyses. Electrochemical studies showed that the Co2+ ions in 1 can be oxidized to Co3+ and the CVs of the W-VI centers of the polyanions feature well-defined and chemically reversible reduction waves. Magnetic measurements on 1 and 2 showed paramagnetism with complex ferromagnetic and antiferromagnetic interactions. A model was presented for extracting the exchange constants for the magnetic exchange interaction.