An equatorial tri-iron substituted Wells–Dawson type tungstophosphate with magnetic and bifunctional electrocatalytic properties

Interaction of the hexa-lacunary polyanion precursor [α-H2P2W12O48]12− and the FeIII in aqueous solution results in the formation of an equatorial tri-iron substituted Wells–Dawson type compound, K4Cs2Fe2[P2W15(FeOH)3O59]·22H2O (1). Compound 1 was characterized by IR, elemental, single-crystal X-ray diffraction, thermogravimetric, magnetic, as well as electrochemical analysis. The polyoxoanion [P2W15(FeOH)3O59]12− can be viewed as a derivative of the parent polyoxoanion [α-P2W18O62]6− by removal of three belt WO groups and then inhabited by three FeOH groups. The compound 1-modified carbon paste electrode (1-CPE) presents good electrocatalytic activity not only toward the reduction of nitrite which is attributed to the function of tungstophosphate, but also toward the oxidation of ascorbic acid which is primarily attributed to the function of FeIII. The magnetic properties of 1 have been studied by magnetic susceptibility and fitted according to an isotropic exchange model. Compound 1 exhibits strong antiferromagnetic spin exchange interactions between the FeIII centers.