Inorganic–organic hybrid supramolecular architectures based on Keggin polyoxometalates and crown ether: synthesis, crystal structure and electrochemical properties

Two novel supramolecular assemblies built from Keggin-type polyoxometalate and [18]-crown-6 ether building blocks, (K+)4([18]-crown-6)4(CH3CN)2[SiM12O40] (M = Mo (1), W (2)), have been synthesized and characterized via single-crystal/powder X-ray diffraction and a wide range of analytical methods, including FT-IR, UV-vis, Raman, and NMR spectroscopy, thermogravimetric analysis, and density functional theory (DFT) calculations. This POM-based supramolecular architecture is the first example of a Keggin-type POM linked to four 18-crown-6 components forming unique propeller-like supramolecular host–guest structures via crown–metal–O(POM) bonds in the forms of the isostructural compounds 1 and 2. In addition, the electrochemical behaviors and electrocatalytic properties toward the reduction of sodium nitrite (NaNO2) were also investigated via cyclic voltammetry in acidic solution.