A complex based on a decorated Keggin-type cluster from Cu(II) and 4,4′-dimethyl-2,2′-bipyridine: synthesis, structure and proton conductivity

A proton-conductive complex based on decorated Keggin-type cluster, {[Cu(dmbipy)(H2O)3]2[SiW12O40]}·7H2O (where dmbipy is 4,4′-dimethyl-2,2′-bipyridine) (1), was synthesized by reaction of CuSiW12O40·nH2O and dmbipy at room temperature. The product was characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction analysis. Single-crystal X-ray diffraction analysis at 293 K revealed that 1 crystallized in the monoclinic space group C2/c and has a 3-D supramolecular network with 1-D hydrophilic channels constructed by a decorated Keggin-type cluster, [Cu(dmbipy)(H2O)3]2SiW12O40, and solvent water molecules via hydrogen-bonding interactions. Thermogravimetric analysis suggests that 1 has high-thermal stability and good water binding in 1-D hydrophilic channels from 20 to 100 °C. Compound 1 exhibits good proton conductivities (over 10−3 S cm−1) at 100 °C in the relative humidity range 35–98%.