A supramolecular complex based on poly-Keggin-anion chains: synthesis, structure characterization, and conductivity

Abstract  

A proton-conductive supramolecular complex, {Cu(H₂O)₈]H(H₂O)₃](HINO)₄(PMo₁₂O₄₀)} _n , was constructed by a self-assembly of H⁺(H₂O)₃ clusters, Cu(H₂O)₈]²⁺ clusters, PMo₁₂O₄₀]³⁻ anions, and isonicotinic acid N-oxide (HINO). Single-crystal X-ray diffraction analysis at 293 K revealed that the complex presented the three-dimensional (3D) supramolecular framework built from non-covalent interactions. Interestingly, PMo₁₂O₄₀]³⁻ anions self-assembled into poly-Keggin-anion chains in the supramolecular framework. Thermogravimetric analysis shows no weight loss in the temperature range of 20–100 °C, indicating that all water molecules in the unit structure are not easily lost below 100 °C. Surprisingly, the proton conductivity of the complex in the temperature range of 85–100 °C under 98% RH condition reached good proton conductivity of 10⁻³ S cm⁻¹. A possible mechanism of the proton conduction was proposed according to the experimental results.