Unprecedented {Fe14 }/{Fe10 } polyoxotungstate-based nanoclusters with efficient photocatalytic H2 evolution activity: synthesis, structure, magnetism, and electrochemistry

Singh, V., Chen, Z., Ma, P., Zhang, D., Drew, M. G. B., Niu, J. and Wang, J. (2016) Unprecedented {Fe14 }/{Fe10 } polyoxotungstate-based nanoclusters with efficient photocatalytic H2 evolution activity: synthesis, structure, magnetism, and electrochemistry. Chemistry- A European Journal, 22 (31). pp. 10983-10989. ISSN 1521-3765 doi: 10.1002/chem.201601453

Abstract/Summary

Novel Fe10 and Fe14 clusters [Rb9Cs4H37Fe10O34(A-α-PW9O31)3(OH)3]⋅36 H2O (1) and [H3Rb3Fe14(OH)12(PO4)6(B-α-PW9O34)2]⋅21 H2O (2) were synthesized and characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis (TGA), and magnetic studies, and in solution by electrochemistry. Cluster 1 is a decameric FeIII polyanionic cluster encapsulating a cesium atom in the center. Cluster 2 is a unique tetradecanuclear FeIII sandwich structure with phosphate-linked units featuring two quasicubic Fe4O4 moieties. Apparently, 2 has the highest nuclearity of all known FeIII sandwich-type polyoxometalate clusters. Clusters 1 and 2 also act as photocatalysts with platinum as cocatalyst for H2 evolution from light-driven water splitting. Changes in the cyclovoltammetric patterns with variations in pH were observed for 1 and 2, most likely due to intermolecular interactions among the high-nuclearity FeIII cluster cores and subsequent changes in the acid–base properties of the two reduced POMs. Magnetic studies provide evidence of antiferromagnetic interactions in 1 and 2. TGA showed that complexes 1 and 2 decompose between 580 and 590 °C.