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

Abstract

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%.

Keywords:

• Polyoxometalates
• crystal structure
• supramolecular network
• 4,4′-dimethyl-2,2′-bipyridine
• proton conductivity

Funding

This work was supported by the National Natural Science Foundation of China [grant number 21171050], [grant number 201501047]; the Program for Innovative Research Team (in Science and Technology) in University of Henan Province [grant number 13IRTSTHN026].

Disclosure statement

No potential conflict of interest was reported by the authors.