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. A good proton-conductive supramolecular complex was built from non-covalent interactions among HINO molecules, [Cu(H2O)8]2+ and H+(H2O)3 clusters, and [PMo12O40]3− anions, as well as its structure was determined by using single-crystal X-ray diffraction data.