Designs, Synthesis And Property Of Inorganic-Organic Hybrid Proton Conductor Based On Heteropoly Salt

Heteropoly acid is a class of multi-core complex with oxygen bridge. in the solid state, it is mainly composed of protons, heteropoly anions and water (structural water and crystal water). Keggin structure heteropoly acid ion has a unique structure, is an excellent low-temperature proton conducting electrolyte.The main content of this paper is designed and synthesized a series of inorganic-organic complex based on the Keggin type polyanions building blocks. First, We succeeded in constructing six proton conducting inorganic–organic hybrid complexes by the self assembly of protonated water clusters, transition-metal ions water clusters, Keggin-type polyanions and isonicotinic acid N-oxide(HINO),namely, compounds 1-6. These compounds have been tested by the spectra Characterization, thermal analysis, crystallographic characterization, proton conductivity testing, and so on. They presented exactly the same 3D supramolecular frameworks by non-covalent interactions among organic molecules HINO, protonated water clusters H+(H₂O)n(n=2,2.5,3), transition-metal ions water clusters [M(H₂O)₈]²⁺(M=Co,Ni,Mn,Zn,Cu) and Keggin-type polyanions. Keggin-type polyanions, transition-metal ions water clusters, and protonated water clusters are regularly dispersed in the hydrogen bond network structures build by organic molecules HINO. Interestingly, Keggin-type polyanions formed one-dimensional polymeric anion. UV spectroscopy results showed that these compounds are insoluble in water; TG results showed that these compounds are stable below 100°C, the structure did not change. Although the loss of crystal water, its structure is relatively stable in 200°C; X-ray powder diffraction data showed that the proton conductivity of powder samples have the same super-molecular skeleton before and after the measurements, these compounds have not changed; Infrared analysis showed that the Keggin-type polyanions in the compounds and organic molecules HINO are free, the hydrogen bond network structure did not change. The conductivity of these compounds was the non-covalent anionic synergism results between organic molecular HINO, water clusters and Keggin-type polyanions. AC impedance test results showed that six compounds reached high proton conductivities 10^-3 S·cm^-1 in the temperature range 85-100°C under relative humidity 98%. The results shows that compounds 1-6 have a good conductivity, is a new type of low-temperature proton conducting materials.Secondly, an inorganic-organic compound was synthesized by N,N'-dioxide-4,4'-bipyridine (dpdo) as a ligand, metal rubidium ion Rb+ and Keggin-type polyanions, that is, compound 7. Keggin-type polyanions, coordination cations, protonated water clusters appeared alternately, they were dispersed in layered structure with hydrogen bond network construced by the organic molecular dpdo, forming a 3D inorganic-organic compound with a special 1D channel.Finally, We are synthesized two types supramolecular compounds based on Keggin-type polyanions and Metal-Schiff base coordination cations with 1,4-bis(4-imidazolyl)-2,3-diaza-1,3-butadiene (ligand L), transition metal nickel ions Ni²⁺ and Keggin-type polyanions. In compounds 8-9, Metal-Schiff base coordination cations formed cation layers by hydrogen-bonding, Keggin-type polyanions formed anionic layers, cation layers are alternately appeared with anion layers. Heteropolyanions not only influenced formation of the Metal-Schiff base Coordination cations, but also plays a role in balancing the charge.