Two proton-conductive hybrids based on 2,2′-biimidazole molecules and Keggin-type heteropolyacids

Two proton-conductive organic/inorganic complexes were constructed by Keggin-type heteropolyacids and 2,2′-biimidazole molecules. Single-crystal X-ray diffraction analyses revealed that two complexes crystallized in the triclinic space group Pī, exhibited very close unit cell parameters, and presented similar three-dimensional (3D) hydrogen-bonded networks constructed by H2biim, [PM12O40]3− (M=W for 1 and Mo for 2) and solvent molecules. The results of thermogravimetric analyses (TG) suggest that two supramolecular complexes have similar thermal stability based on the same 3D packing. Two complexes at 100 °C under 98% relative humidity showed a good proton conductivity of about 10−4 S cm−1. A possible mechanism of the proton conduction was proposed according to the experimental results.