PH-Directed assembly of four polyoxometalate-based supramolecular hybrids by using tritopic bridging ligand 1, 3, 5-tris-(1-imidazolyl)-benzene: Structures and electrocatalytic properties

Abstract

Four new inorganic-organic supramolecular compounds, namely, (H2tib)2[GeW12O40] (1), [Mn(Htib)4][HGeW12O40]2·4H2O (2), [Mn(tib)]2(H2O)6[GeW12O40]·4H2O (3) and [Mn(tib)]2(H2O)6[GeW12O40]·2H2O (4) (tib = 1, 3, 5-tris-(1-imidazolyl)-benzene), have been synthesized through the hydrothermal reaction of [GeW12O40]4- anions, MnII cations and tib ligands under different pH conditions. Compounds 1 and 2 were prepared at lower pH (pH ≈ 2.0 for 1 and 3.2 for 2). Compound 1 exhibits a simple monomer structure. In 2, the Mn cation is coordinated with four tib ligands and two [GeW12 O40]4- anions to form a dimer, in which each of [GeW12 O40]4- anion connects with one Mn cation. Compounds 3 and 4 were prepared at higher pH (pH ≈ 4.2 for 3 and 4.9 for 4), and compounds 3 and 4 display a one-dimensional (1D) chain and a (4, 4)-connected 2D wave-like layer, respectively, and in compound 3, each of GeW12 cluster connects two Mn atoms, however, compound 4: each of GeW12 cluster connects four Mn atoms. The isolation of these four compounds is very informative for systematically understanding the effect of the pH on assembly of polyoxometalate-based hybrids. Also, the electrocatalytic properties of 1–4-CPEs towards nitrite have also been investigated.