Synthesis And Properties Of Metal Complexes Based On Pyridyl Isophthalic Acid Ligands

The study of metal-organic frameworks?MOFs?has attracted much attention due to its excellent magnetic properties,luminescence and porosity.The pyridine dicarboxylic acid ligands contain a plurality of nitrogen atoms and oxygen atoms,with abundant coordination sites,strong coordination ability,and flexible coordination modes.Pyridine group has a rigid conjugate plane,which may produce good fluorescence after coordination.The carboxyl group has a negative charge after losing the proton.The oxygen atom can transfer magnetic coupling when it is coordinated with the metal ion.The carboxylate bridges the metal cation in different coordination modes,which may exhibits different magnetic behavior.By assembling the pyridyl group and the carboxyl group in the same molecule,it is easier to obtain a novel molecular structure and more unique magnetic and fluorescent properties.In this thesis,pyridine dicarboxylic acid ligands were used as a research object,and 8 functional complexes were synthesized,the magnetic and fluorescent properties of these complexes were excellent.The research work is mainly divided into the following parts:1.Study on the fluorescence of transition metal ions complexes of5-?4-pyridylamino?isophthalic acid.Two luminescence coordination polymers?CPs?formulated as{[Zn?L¹??H₂O?₂]·H₂O}_n?1?and{[Cd?L¹??H₂O?₂]·4H₂O}_n?2?are successfully prepared by solvothermal reactions between the corresponding metal?II?ions and5-?4-pyridylamino?isophthalic acid?H₂L¹?.Crystallographic studies reveal that 1 and2 exhibit similar 2D honeycomb layer networks,but have different numbers of lattice water molecules.The layers are connected through hydrogen bonds to give 3D supramolecular frameworks.CPs 1 and 2 possess coordinated water molecules and uncoordinated oxygen atoms as well as electron-rich amide groups,which are easy to recognize diverse analytes.Moreover,they show considerable stability in aqueous systems with a broad pH range from 3 to 12.Luminescence sensing experiments indicate that they can be regarded as highly sensitive sensors for detecting Fe³⁺ions,Cr^VI-anions(CrO₄^2-and Cr₂O₇^2-)and 2,4,6-trinitrophenol?TNP?through luminescence quenching.In addition,the mechanisms for the luminescence response of CPs 1 and 2 towards Fe³⁺ions,Cr^VI-anions and TNP have been investigated in detail.Besides,CPs 1 and 2 represent two very good examples of versatile Zn/Cd-CP probes capable of sensing Fe³⁺ions,Cr^VI-anions and TNP.2.Study on the fluorescence and magnetic properties of Ln?III?ions complexes of 3-?3,5-dicarboxylphenoxy?pyridine.Six new two-dimensional isostructural lanthanide coordination polymers(Ln ^III-CPs),[Ln₂?L?₃?H₂O?₃]·DMF?Ln=Sm?3?,Eu?4?,Gd?5?,Tb?6?,Dy?7?and Ho?8?,H₂L²=3-?3,5-dicarboxylphenoxy?pyridine?,have been fabricated successfully under solvothermal conditions.In these compounds,Ln ^IIIII ions are linked by the mixed(?-O_carboxylate)?COO?₂ triple bridges to give dinuclear motifs.The motifs are connected through single carboxylate bridges to give alternating chains,and the chains are interlinked by the L² ligands to produce 2D layers.Their structures with accessible Lewis-base site and coordinated water molecules exhibit easily recognize various analytes.The dc magnetic susceptibility studies for Gd-CP?5?and Ho-CP?8?reveal the occurrence of probable antiferromagnetic interactions,but for Dy-CP?7?shows ferromagnetic interactions.Further investigations suggest that Dy-CP?7?displays slow magnetic relaxation behavior with the energy barrier(?U_eff)and the pre-exponential factor??₀?of 25.47 K and 1.25×10^-66 s at 1200 Oe dc field,respectively.The luminescence explorations suggest that Eu-CP?4?and Tb-CP?6?can exhibit high quenching efficiency and low detection limit for sensing Fe³⁺,MnO₄^-,Cr^VI-anions(CrO₄^2-,Cr₂O₇^2-)and 2,4,6-trinitrophenol?TNP?in water systems.Moreover,in the process of detecting analytes,Eu-CP?4?and Tb-CP?6?not only exhibit the excellent water stability and strong luminescence,but also own remarkable circularity and regeneration.