Magnetism And Fluorescence Properties Research Of Functional Coordination Polymers Based On Rigid Nitro-biphenyl Carboxylic Acid And Pyridine Carboxylic Acid Ligand

Metal-organic Fremaworks(MOFs)have been an important member of Coordination Polymers(CPs)because of its extensive applications prospect.Since the 1990s,MOFs have been developed with a rapid speed.Researchers have made great efforts to study and summarize the numerous and complicated structures of new MOFs,and nowadays their research focusesare gradually transferring to the exploitation of potential applications of MOFs.Therefore,functional MOFs with gas adsorption/separation,molecular recognition,catalysis,magnetism and other excellent properties were widely constructed and studied.The self-assembly of MOFs is influenced by many factors.Speaking of which,organic ligands play a very important role in obtaining novel structures and prospective properties of the target MOFs,owing to their different molecular sizes,functional groups,coordination sites and the symmetry difference,etc.,especially for the rigid carboxylic acid and functionalization N-heterocyclic carboxylic acid ligands with flexible coordination models and more varied coordination sites.Above mentioned organic ligands are often utilized to build MOFs with variable structures,excellent properties and stable skeletons.In addition,the electron configuration of the center metal ions have also been a decisive elements during constructing procedure of the functional MOFs.Thus,lanthanide metal ions are usually regarded as a good candidate to build high-performance complexes,which has special performance in magnetic and fluorescence due to its unique 4f orbit.Following the building strategy above,we choose biphenyl-3'-nitro-3,4',5-tricarboxylic acid(H3L1)ligand,2-(3,5-dicarboxylphenyl)-5-carboxylpyridine(H3L2)ligand and 3-(3,5-dicarboxylphenyl)-6-carboxylpyridine(H3L3)ligand as three building blocks to construct functional MOFs.Based on the theory of crystal engineering of molecular self-assembly,we used solvothermal method successfully synthesized 17 complexes as follows:[LnL1(H2O)3]·3H2O·0.75DMF(1-7)(Ln=Dy(1),Eu(2),Tb(3),Gd(4),Er(5),Ho(6),and Yb(7));[Ln2(L2)2(H2O)4(DMA)]·DMA·3H2O(8-14)(Ln= Dy(8),Eu(9),Ho(10),Tb(11),Gd(12),Yb(13)and Er(14));[Zn4(L1)2(H20)(OH)2](15);[Zn3(L3)2(H20)]·4H20(16);[Zn3(L3)2(bipy)(H2O)6]·2H2O(17).Complexes 1-7 and 8-14 are two series of typical Ln-MOFs,each with the same structure respectively,and with excellent magnetic and optical properties.Single crystal X-ray study showed that structure of complex 15 contains a rare 7 nuclearmetal cluster,and the adjacent metal clusters connected with each other through the ligands,obtaining a three dimensional framework,eventually.Complexesl6 and 17 were designed and built by d10 electron configuration metal of Zn with H3L3 ligand,both of them perform fluorescent properties.All of the complexes have been characterized by the X-ray powder diffraction(PXRD),elemental analysis,infrared spectrum(IR)and thermosgravimetric analysis(TGA).And all of the above mentioned properties have been tested.