<p> Supplementary Materials</p><p>V 2+ A New Molybdophosphate constructed by {Mo 2O4(H2O)6} and 1-</p><p> hydroxyethylidenediphosphonate</p><p>Hua-Qiao Tan · Wei-Lin Chen · Ding Liu · En-Bo Wang</p><p>Figure S1. Polyhedral and ball-and-stick representation of polyoxoanion 1. Figure S2. Polyhedral and ball-and-stick representation of the 3D supramolecular structure of compound 1. Figure S3. Polyhedral and ball-and-stick representation of the 3D supramolecular structure of compound 1 viewed from a axis.</p><p>Figure S4. Polyhedral and ball-and-stick representation of the 3D supramolecular structure of compound 1 viewed from b axis. Figure S5. Polyhedral and ball-and-stick representation of the 3D supramolecular structure of compound 1 viewed from c axis. Figure S6. The UV-Vis spectrum for compounds 1 in the solid state. Figure S7. The TG curve of 1 exhibits three weight loss stages in the temperature ranges 30-600 °C. The first and second weight loss is 24.28% in the temperature</p><p>+ range 30-353 °C, corresponding to the release of all the NH4 ions and lattice water molecules in 1 (24.29%). After 353 °C, polyoxoanion 1 would be decomposed Figure S8. The cyclic voltammetry curve of compound 1. The electrochemical</p><p> behavior of compound 1 was investigated in pH = 5 (0.5 M H2SO4+Na2SO4) butter solution at the scan rate of 25 mVs-1. The CV of 1 possesses two irreversible redox</p><p> pairs at E1/2 = -0.060 and -1.011 V (E1/2 = (Epa+Epc)/2), which are responsible for redox processes of MoVI [1] and MoV [2] respectively.</p><p>[1] (a) L. Cheng, G. E. Pacey, and J. A. Cox (2001) Electrochimica Acta. 46, 4223; (b)</p><p>P. Wang, X. P. Wang, and G. Y. Zhu (2000) Elelctroanalysis. 12, 1493; (c) P.</p><p>Wang, Y. Yuan, Z. B. Han, and G. Y. Zhu (2001) J. Mater. Chem. 11, 549.</p><p>[2] A. Dolbecq, J. D. Compain, P. Mialane, J. Marrot, F. Sécheresse, B. Keita, L. R. B.</p><p>Holzle, F. Miserque, and L. Nadjo (2009). Eur. Chem. J. 15, 733.</p>