Syntheses,Structures And Proton Conductivities Of Transition Metal Coordination Polymers Based On Flexible Isophthalic Acid Ligands

In recent years,coordination polymers(CPs)have been widely applied in proton conducting materials because of their good crystallinity,structural tunability and good chemical stability.More and more CPs proton conductors have been reported.However,the proton conduction mechanism of complexes is still unclear,so how to obtain CPs with high proton conductivity is the primary problem to be solved in the current proton conductor research.Based on this,this thesis focuses on the synthesis,structure and proton conductivity of CPs,summarizes the synthesis rules and explore relationships between structure and properties,so as to provide a factual reference for the study of proton conductor materials.A series of coordination polymers were obtained through reactions between two polycarboxylic ligands with flexible oxygen-containing substituents and transition metal salts under hydrothermal conditions.The crystal structures,reaction condition,proton conduction and magnetic properties of some complexes were studied.The main work is listed as follows:1.Synthesis,structure and electrochemical properties of transition metal coordination polymers based on 5,5'-(butane-1,4-diylbis(oxy))diisophthalic acid and different nitrogen-containing ligands.Twelve new compounds[M(H₂L1)(bpy Br)₂]·2H₂O(M=Ni 1,Co 3),[M₂(H₂L1)₂(bpy Br₂)₂(H₂O)₃]_n(M=Ni 2,Co 4),[Cu(H₂L1)(bpy Br₂)]_n(5),{[Zn(L1)_1/2(bpy Br₂)(H₂O)]·H₂O}_n(6),{[Zn(H₂L1)(bpy Br₂)]·2H₂O}_n(7),{[Zn(H₂L1)(bpy Br₂)(H₂O)]·H₂O}_n(8),[Ni(L1)_1/2(Mbpy)(H₂O)₂]₂(9),[Cd(H₂L1)(Mbpy)]_n(10),[Ni₂(L1)(Nphen)₂(H₂O)₄]_n(11),[Ni(H₂L1)(bpy)(H₂O)₂]_n(12),has been obtained.Compound 1 and 3 are isomorphic,which are discrete mononuclear compounds,and the structure contains uncoordinated protonated carboxylic acid groups.Hydrogen bonds between the-COOH group and the lattice water molecules connect the discrete units to form 2-D supramolecular layer,there are empty cavities in the 2-D supramolecular layer with the dimensions 6.44?×6.29?.Compound 2 and 4 are isomorphic,which are one-dimensional chain structure.These chains are further connected by complicate hydrogen bonds between the-COOH group and coordination water molecules to form a three-dimensional self-penetrating supramolecular structure.Compound 5 shows a 2-D coordination layered structure.The hydrogen bond between the uncoordinated carboxyl group and the coordinated carboxyl group link those layers to form a 3-D supramolecular network.The long H₄L1 ligand gives the 3-D network a relatively large channel with bpy Br₂ ligand filling in.The compounds 6,7 and 8 all show one-dimensional chains and form three-dimensional supramolecular structures through hydrogen bond interactions.The coordination modes of L1 ligand are different due to different p H values.Compound 9 is a discrete mononuclear molecule whose structure contains uncoordinated carboxylic acid groups.The hydrogen bonds between the-COOH group and the lattice water molecules connect the discrete units to form a three-dimensional supramolecular network structure.The long H₄L1 ligand gives the three-dimensional network structure a relatively large channel,and Mbpy ligand fills it.Compound 10 displays a one-dimensional coordination chain structure.Hydrogen bonds between uncoordinated protonated and coordinated carboxylic acid groups connect those chains to form a two-dimensional supramolecular layer.The 1-D coordination chains of compound 11 have been linked by hydrogen bonds between coordination water molecules and carboxylic acid groups to form a two-dimensional supramolecular layer.In compound 12,the H₂L1^2-and bpy ligands connect metal cations to form a two-dimensional coordination layer,which is further linked by continuous hydrogen bonds between coordination water molecules and carboxylate oxygen atoms to form a three-dimensional supramolecular network structure.We studied the synthesis conditions of the complexes and found that the types of metal ions,the ratio of reactants and the p H value of the system had important effects on the composition and crystal structure of the products.And it was found that changing the ratio of reactants could induce the reversible transformation from crystal state to crystal state between the complexes 1,3 and 2,4,respectively.We also studied the proton conductivity of the compounds 1-5 and 9-12.It is found that all complexes can improve the proton conductivity of the composite membrane at lower temperature.Based on the results of structural analysis,infrared and water absorption tests,we speculate that the hydroscopicity and acidity of the CPs are important factors affecting the proton conductivity of the CPs.2.Synthesis,structure and electrochemical properties of transition metal coordination polymers based on 5,5'-(butane-1,4-diylbis(oxy))diisophthalic acidFour new compounds{[M(L1)_1/2(H₂O)₂]·H₂O}_n(M=Co 13,Mn 15,Zn 16){[Co(L1)_1/2(CH₃OH)₂]·H₂O}_n(14),has been synthesized based on 5,5'-(butane-1,4-diylbis(oxy))diisophthalic acid under hydrothermally synthesis.Compounds 13,15 and 16are isomorphic compounds,and metal cations are connected by carboxylate groups of L1^4-ligands to form two-dimensional coordination layers.Continuous hydrogen bonds between water molecules and the carboxylate oxygen atoms link those 2-D coordination layers to form 3-D supramolecular network.The solvent molecular exchange performance of compound 13 was studied.Based on the X-ray powder diffraction spectrum and the color change of the complex after the exchange,we speculated that the crystals and coordination water in the complex could be exchanged with some organic small molecules such as methanol,ethanol and DMF.Fortunately,we obtained the single crystal structure of compound 14 after the exchange with methanol molecule,and the methanol molecule replaced the water molecule to coordinate with Co(II),which is consistent with our conjecture.The coordination environment change between compounds 13 and 14 is also verified by the difference of their magnetic properties.By studying the electrochemical properties of the three compounds,it can be seen that they exhibit different proton conductivity,indicating that metal ions have certain influence on proton conductivity.3.Synthesis,structure and electrochemical properties of transition metal coordination polymers based on 5,5'-(pentane-1,5-diylbis(oxy))diisophthalic acid and different nitrogen-containing ligands.Fournewcompounds{[Cd(L2)_1/2(H₂O)₂]·2H₂O}_n(17),{[Ni₂(L2)(bpy Br₂)₂(H₂O)₂]·H₂O}_n(18),{[Ni(H₂L2)(bpy)(H₂O)]·H₂O}_n(19),[Co(H₂L2)(bpy)(H₂O)₂]_n(20),has been obtained.In compound 17,L2^4-ligand connects metal ions through its four carboxyl groups to form a three-dimensional network structure with large pores and filled with crystal water molecules.The L2^4-ligand of compound 18connects the metal atoms to form a two-dimensional layer.The H₂L2^2-and bpy carboxylic ligands of compound 19 connect metal atoms to form a two-dimensional layer.Compound20 is a one-dimensional chain structure.In all the compounds,there are abundant hydrogen bonding between coordination or crystalline water molecules and carboxylic acid oxygen atoms.The electrochemical properties of the compounds 17-20 have shown that the doping of all the complexes improves the proton conductivity of the composite membrane to varying degrees.By comparing the proton conductivity of the compounds in this paper,we find that the metal ions,the acidity,the hydroscopicity of CPs and the mobility of the proton carriers all have significant influences on the proton conductivity of the materials.Therefore,acidic functional groups,large pores,free proton carriers and continuous hydrogen bonds are the direction of the design and synthesis of proton conduction materials.In addition,higher proton conduction activation energy should also be what we pursue.