Synthesis,Structure And Proton Conductivity Of Transition Metal Coordination Polymers Based On Imidazole/Pyridyl Isophthalic Acid Ligands

In the past decades,the design and synthesis of transition metal coordination polymers have received substantial attention,not only for their particular beauty and intriguing structure diversities of architecture,but also for their underlying application in gas storage,luminescence,catalysis,magnetism and electrochemistry etc.As far as we known,organic ligands,metal ions,solvent and temperature that could have influence on the ultimate structure,the rational design and synthesis of novel coordination polymers with unique structure or particular functions is still a great challenge.To further explore relationships between synthesis,structure and properties,we selected three series of nitrogen-containing carboxylic ligands.Based upon these ligands,a series of coordination polymers with unique structure were obtained through reaction with transition metal ions under hydrothermal conditions.The luminescence,magnetism and electrochemistry of some compounds have also been studied.The main work is listed as follows:1.Four new compounds,{[Cd?L1??H₂O?]·0.5H₂O}n?1?,{[Zn?L1??H₂O?]·H₂O}n?2?,{[Co?L1??H₂O?₂]·2H₂O}n?3?,{[Ni?L1??H₂O?₂]·2H₂O}n?4?has been synthesized based on 5-?1-H-imidazole-1-yl?isophthlate acid?H2L1?under hydrothermally synthesis.Compound 1 shows a 3-D framework,Compounds 2-4 all adopt 2-D layer structure,which were linked into 3-D superamolecular network by hydrogen bonding interactions.The higher dimension of compound 1 may be caused by the greater ionic radius and the higher coordination number of Cd?II?ion.2.Seven new compounds,{[Zn?L2?]·0.5H₂O}n?5?,{[Cd?L2?]·0.5H₂O}n?6?,{[Zn₂?L3?₂]}n?7?,{[Cd?L3?]}n?8?,{[Cd?L3??H₂O?]·2H₂O}n?9?,{[Cd?L3??H₂O?]}n?10?,{[Cd?L3?]}n?11?has been synthesized based on 5-?pyridin-2-ylmethoxy?isophthalicacid?H2L2?and 5-?pyridin-4-ylmethoxy?isophthalic acid?H2L3?.Compound5-6 both present a 2-D layer structures.Compound 9,10 present 2-D layer structures,which were linked into 3-D superamolecular framework by hydrogen bondinginteractions.Compounds 7,8,11 all show 3-D framework.Comparing the structure characteristics of compounds 8-11,it can be concluded that with the rising of pH value,Cd?II?has a higher coordination number,and the ligand can connected more metal ions.The presence of coordination or lattice water molecules or not greatly affects the crystal packing of coordination compounds.3.Three new compounds,{[Zn_1.5?L4??H₂O?₂]·H₂O}n?12?,{[Zn3?L4?₂?H₂O?₄]·3H₂O}n?13?,{[Cd_1.5?L5?}n?14?has been synthesized based on3-?3,5dicarboxylphenyl?-6-carboxylpyridine?H2L4?and2-?3,5dicarboxylphenyl?-6-carboxylpyridine?H2L5?.Compound 12 adopt 2-D coordination layer,while compounds 13-14 both show a 3-D framework.Comparing the structure characteristics of compounds 12-14,it was found that the coordination number of Zn?II?ions increased with the increasing of temperature which can result in the high dimensional packing.4.The properties of some compounds were studied.?1?.Luminescent properties.The solid-state luminescent measurements of compounds 1-2 indicated compounds 1-2 have good fluorescence properties.?2?.Magnetic properties.The magnetic susceptibility measurements of compounds3-4 indicate the antiferromagnetic interactions between Co???ions in compound 3,the weak ferromagnet interactions between Ni?II?ions in compound 4.?3?.Proton conduction properties.The proton conductivities of composite membrane mixed by Nafion and compounds 1-8,12,14 were measured by AC impedance spectroscopy in pure water and sulfuric acid.The results reveal that these compounds can affect the proton conductivity of Nafion membrane in different degrees,which may be caused by the different crystal packing of these compounds.Proton conductivity increased with the enhancement of working temperatures and concentration of H+ ions.?4?.The H₂O₂ electrochemistry sensing properties of compounds 3 were researched.The H₂O₂ sensing properties of compound 3 were tested in 0.1M mol NaOH solutions.The result suggests that compound 3 possesses a high sensitivity towards H₂O₂ reduction.