关键词: 杂多酸, 晶体结构, 超分子复合物, 传导材料, N-氧化吡啶-4-甲酸

One organic/inorganic hybrid complex {[Co(H₂O)₈][H(H₂O)₃](HINO)₄(PW₁₂O₄₀)}_n, was constructed by a self-assembly of H⁺(H₂O)₃ clusters, [Co(H₂O)₈]²⁺ clusters, [PW₁₂O₄₀]^3- anions and isonicotinic acid N-oxide (HINO). It was characterized by X-ray diffraction analysis, elemental analysis, IR, TG, UV, XRD, proton conductivity analysis. In the synthetic procedure of title complex, a mixture of result heteropolyacid cobalt salts CoHPW₁₂O₄₀·nH₂O (90 mg, 0.03 mmol) and HINO (17 mg, 0.12 mmol) was dissolved in enough acetonitrile/water (1∶1, V/V) to form a homogeneous solution. Finally, the solution was filtered and the solvent left to evaporate at room temperature. A week later, light red crystals appeared and were collected and dried in air after quickly being washed with water. Single-crystal X-ray diffraction analysis at 293 K showed that complex 1 crystallizes in orthorhombic crystal system, Pnnm, and there was exactly a three-dimensional (3D) hydrogen-bonded network with large one-dimensional (1D) channels, in which [PW₁₂O₄₀]^3- anions just filled in the 1D channels and self-assembled into poly-Keggin-anion chains. The result of the UV spectra indicates that the saturated aqueous concentration of 1 is ca. 10^-5 mol/L and it is insoluble in water. Thermogravimetric analysis shows no weight loss in the temperature range of 20～100 ℃, indicating that all water molecules in the structure are not easily lost below 100 ℃. The powder X-ray diffraction data exhibits that although crystallized water molecules are lost at 200 ℃, the evacuated complex has the same structure as the single-crystal of 1. Moreover, the powder sample after the proton-conductive measurement has the same supramolecular framework as that of complex 1. Interestingly, the title complex was characterized by a satisfactory ionic conductivity (1×10^-3～2×10^-3 S·cm^-1) in the temperature range of 85 to 100 ℃ only. The mechanism of proton conduction of the title complex is, expected to be similar to that of the vehicle mechanism, that is, the direct diffusion of additional protons with water molecules (Grotthuss mechanism).

Key words: polyoxometalate, crystal structure, supramolecular complex, conducting materials, isonicotinic acid N-oxide