Syntheses And Properties Of The Clusters Based On Heteropoly Salts And 2,2'-bipyridine Derivatives

Solid proton conductors is a kind of important functional materials using protons as charge carriers.They can be used as a variety of solid electrolyte electrochemical devices,including the hydrogen fuel cell,the electrolyte,biological medicine etc and have important application value and broad application prospects.Typically,Keggin-type heteropoly acid consisting of protons and heteropoly anion is a kind of good low temperature proton conductor.Organic molecules 2,2 '-pyridine derivatives?4,4'-dimethyl-2,2 '-pyridine and 2,2'-Bipyridine-4,4'-dicarboxylic acid?can be used as a kind of good organic ligands.The substituentments of 4,4'-dimethyl-2,2 '-pyridine are hydrophobic methyl groups;the substituentments of2,2'-Bipyridine-4,4'-dicarboxylic acid are hydrophilic carboxylic groups which itself can also provide protons.In this case,we assume that combined the Keggin-type heteropoly acid salt with two kinds of 2,2 '-pyridine derivatives together to form the decorated heteropoly anion clusters.These clusters may be good proton conductors.In this paper,we have successfully synthesized two decorated heteropoly anion clusters that based on Keggin-type heteropolyacids,transition metal ions Cu²⁺ and 4,4 '-dimethyl-2,2'-pyridine?dmbipy?.The two compounds were characterized by elemental analysis,single-crystal X-ray diffraction analysis,infrared spectroscopy,thermogravimetric analysis,X-ray powder diffraction analysis.Among them,Single-crystal X-ray diffraction analysis at 293 K revealed that these two compoundswere:{[Cu?dmbipy??H₂O?₂Cl_0.5][PW₁₂O₄₀]}2·7H₂O?compound1?and{[Cu?dmbipy??H₂O?₃]₂[SiW₁₂O₄₀]}·7H₂O?compound 2?,and the two compounds were crystallized in the monoclinic space group C2/c and presented a 3D supramolecular network with 1D hydrophilic channels constructed by decorated Keggin-type cluster,heteropoly acid anion and 4,4 '-dimethyl-2,2'-pyridine played as a bidentate ligand exist in the structure of clusters;Infrared spectrum data showed the characteristic peaks of organic ligand and heteropoly anion;The result of thermogravimetric analysis suggests that compound 1 and compound 2 has high thermal stability and good water holding in 1D hydrophilic channels in the temperature range 20¹00 °C;The results of A.C impedance of the two compounds indicated that they have achieved good proton conductivities?10-4¹0-3 S·cm-1?in the temperature 100 ° C under relative humidity range 35%-98%;X-ray powder diffraction analysis data indicated that the sample structure of the compound 1 and compound 2 did not change before and after the conductivity measurement.In the second part,we constructed another two decorated heteropoly anion clusters that based on 2,2'-bipyridine-4,4'-dicarboxylic acid?H₂bpdc?,transition metal ions Cu²⁺ and Keggin-type heteropolyacids,{[Cu?H₂bpdc??H₂O?₂Cl_0.5]₂[PW₁₂O₄₀]}·7H₂O?compound 3?and{[Cu?H₂bpdc??H₂O?₃]₂[SiW₁₂O₄₀]}·7H₂O?compound 4?.The two compounds were characterized by elemental analysis,single-crystal X-ray diffraction analysis,infrared spectroscopy,thermogravimetric analysis,X-ray powder diffraction analysis.Single-crystal X-ray diffraction analysis at 293 K revealed that these twocompounds crystallized in the monoclinic space group C2/c and presented a three-dimensional supramolecular network with one-dimensional hydrophilic channels constructed by Keggin-type cluster and solvent water molecular via the short atom××× atom separations in the polymeric polyanion,the disorder of Cl atoms and O atoms,as well as the hydrogen-bonding interactions.The heteropoly acid anion and2,2'-Bipyridine-4,4'-dicarboxylic acid showed as a bidentate ligand exist in the structure of clusters;Infrared spectrum data showed the characteristic peaks of organic ligand of 2,2'-Bipyridine-4,4'-dicarboxylic acid and the heteropoly anion;Thermogravimetric analysis suggests that compound 3 and compound 4 has high thermal stability and good water holding in 1D hydrophilic channels below 100 °C,it suggested that the frame structure was stable and not damaged;X-ray powder diffraction analysis data indicated that the sample structure of the compound 3 and compound 4 did not change before and after the conductivity measurement;The A.C impedance test results of the two compounds indicated that the compounds achieved good proton conductivities(about 10^-410^-3 S·cm^-1)in the temperature 100 ° C under relative humidity range 35-98%.