Synthesis, structure, electrochemistry and magnetism of cobalt-, nickel- and zinc-containing [M(OH)(HO)(α-SiWO)] (M = Co, Ni, and Zn).

Interaction of the trilacunary 9-tungstosilicate [A-α-SiWO] 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-containing heteropolytungstates [M(OH)(HO)(α-SiWO)] (M = Co (1), Ni (2), and Zn (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 Co ions in 1 can be oxidized to Co and the CVs of the W 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.