Assembly of Three Ni<sup>II</sup>–Bis(triazole) Complexes by Exerting the Linkage and Template Roles of Keggin Anions

Three inorganic–organic hybrid compounds based on Keggin-type polyoxometalate (POM) and Ni<sup>II</sup>-bis(triazole) complexes, namely, [Ni<sub>2</sub>(<b>L</b><sup><b>1</b></sup>)<sub>4</sub>(SiW<sub>12</sub>O<sub>40</sub>)]·H<sub>2</sub>O (<b>1</b>), [Ni<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>(<b>L</b><sup><b>2</b></sup>)<sub>4</sub>(H<b>L</b><sup><b>2</b></sup>)<sub>2</sub>][PMo<sub>12</sub>O<sub>40</sub>]<sub>2</sub>·2H<sub>2</sub>O (<b>2</b>), and [Ni<sub>3</sub>(<b>L</b><sup><b>1</b></sup>)<sub>5</sub>][PMo<sub>12</sub>O<sub>40</sub>]<sub>2</sub>·14H<sub>2</sub>O (<b>3</b>) (<b>L</b><sup><b>1</b></sup> = 1,4-bis(1,2,4-triazol-1-yl)butane, <b>L</b><sup><b>2</b></sup> = 1,6-bis(1,2,4-triazol-1-yl)hexane), have been obtained under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compound <b>1</b> exhibits a (6<sup>6</sup>) three-dimensional (3D) Ni-<b>L</b><sup><b>1</b></sup> framework with hexagonal channels, in which [SiW<sub>12</sub>O<sub>40</sub>]<sup>4–</sup> anions have been accommodated as tetradentate linkages. In compound <b>2</b>, the Ni-<b>L</b><sup><b>2</b></sup> motif exhibits a 3D supramolecular network templated by [PMo<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> (PMo<sub>12</sub>) anions. In compound <b>3</b>, the Ni-<b>L</b><sup><b>1</b></sup> motif is a two-dimensional (2D) layer, which is linked by PMo<sub>12</sub><sup>a</sup> anions to construct a 3D framework. The 3D frameworks interpenetrate with each other to form a 2-fold interpenetrating structure, which exhibits two kinds of channels. The other discrete PMo<sub>12</sub><sup>b</sup> anions, acting as inorganic templates, are embedded in the larger channels. The Keggin anions in <b>3</b> exert not only linkage but also template roles. In addition, electrochemical properties of <b>1</b>-bulk modified carbon paste electrode (<b>1</b>–CPE) and <b>3</b>–CPE have been studied in 1 M H<sub>2</sub>SO<sub>4</sub> aqueous solution.