Synthesis, Crystal Structure and Electrochemical Properties of a New Adduct of Benzo-15-crown-5 and H3PMo12O40

A new crown ether-POM (POM = polyoxometalate) adduct with the molecular formula [(C14H20O5)4(H3O)3]PMo12O40 · 0.5CH3CN (1) was isolated from the mixed solvent of acetonitrile and methanol. The adduct is constructed from Keggin [PMo12O40]3− anions and [(C14H20O5)(H3O)] and [(C14H20O5)2(H3O)] cations via electrostatic and hydrogen bonding interactions. The supramolecular interactions combine the crown ether with oxonium ions. In the [(C14H20O5)(H3O)] moieties, the oxonium ions reside out of the planes defined by the oxygen atoms of the crown ether. The [(C14H20O5)2(H3O)] moieties exhibit a sandwich structure. There exist hydrogen bonds between the oxonium ions of the [(C14H20O5)(H3O)] cations and the acetonitrile molecules and the terminal and bridging oxygen atoms of the [PMo12O40]3− anions. The adduct has been used as a bulk-modifier to fabricate a chemically modified carbon paste electrode (MCPE), which displays well-defined cyclic voltammograms with three reversible two-electron redox couples in acidic aqueous solution, and electrocatalytic activities towards the reduction of H2O2 and NO2−.