A series of POM-based hybrid materials with different copper/aminotriazole motifs

By controlling the reaction temperature, pH value of the system and the polyanion templates, three inorganic-organic hybrid materials based on Keggin polyoxometalate building blocks combined with Cu^I/II and 4-amino-1,2,4-triazole (4atrz) have been obtained by hydrothermal methods, namely, [Cu₃(μ₃-OH)(4atrz)₆][SiW₁₂O₄₀]·I·3H₂O (1), [Cu₄(4atrz)₆][SiW₁₂O₄₀] (2) and [Cu₆(4atrz)₆][PMo₁₂O₄₀]₂·H₂O (3). Crystal structure analysis reveals that the Cu^I/II/4atrz complexes in the three materials show tri-, tetra- and hexanuclear models, respectively. In compound 2, the copper clusters link the polyoxometalates into the chains by weak Cu-O bonds; while in the compounds 1 and 3, the copper clusters and the polyoxometalates stack by the ionic interactions. These compounds are further characterized by powder XRD, elemental analyses, FT-IR and thermogravimetric (TG) analyses. The electrochemical behavior of 3-CPE has been studied in the 1 M H₂SO₄ solution. The results exhibit that there are four pairs of redox waves attributable to the four consecutive two-electron processes of Mo(VI/V) couples and the redox process is surface-controlled.