Synthesis,Structure And Properties Of Functional Compounds Of5-(4-carboxyphenyl)Pyridine-2-carboxylic Acid

Aromatic carboxylic acid ligands have a variety of coordination modes due to the inclusion of N and O.In recent years,compounds with metal ions have been widely used for gas adsorption,dye adsorption,photocatalytic materials,and magnetism.Therefore,the study of rigid aromatic carboxylic acid compounds is of great significance.In this paper,5-?4-carboxyphenyl?pyridine-2-carboxylic acid?H₂cppc?was selected as an organic ligand.By reacting with transition metals and lanthanide ions,eight novel structures were successfully constructed and carried out.Single crystal X-ray diffraction,elemental analysis,infrared spectroscopy,powder X-ray diffraction,thermogravimetry,etc.In addition,the compounds was subjected to fluorescence performance,adsorption dye,and gas adsorption test.The main contents are as follows:1.5-?4-carboxyphenyl?pyridine-2-carboxylic acid?H₂cppc?was selected as the organic ligand,and the transition metal Pb was used as the metal ion.Two novel compounds[Pb?cppc?]_n?1?and[Pb₃?cppc?₂?Cl??NO₃?]_n?2?were successfully constructed.Higher temperatures?160??favors the formation of compound 1,while lower temperatures?120??tends to result in the formation of compound 2.Further,the compound 1 is a two-dimensional?2D?double-layer skeleton containing a 1D-Pb-O-Pb-inorganic chain,and the compound 2 is composed of an inorganic-Pb-O-Pb-layer and cppc^2-simultaneously as a pillar of unlimited3D column frame.Solid-state fluorescence showed that at 270 nm excitation,significant blue light emission of compounds 1 and 2 were observed by the naked eye,which was attributable to n??*and???*transfer in the ligand.2.5-?4-carboxyphenyl?pyridine-2-carboxylic acid?H₂cppc?is selected as the organic ligand,and the lanthanide metal?Eu,Tb,Gd,Pr,Dy?is used as the metal ion.Six novel structural compounds Ln-MOFs?3-8?were successfully constructed.In compounds 4-7,the Ln cation employs four carboxylate oxygen atoms,and the two nitrogen atoms coordinate with two oxygen atoms from water.Each cppc^2-anion connects two Ln?III?cations via two carboxylic acid groups and one pyridyl N atom to form a two-dimensional diamond-shaped mesh layer.The adjacent layers are bridged together by strong hydrogen bonding interactions between the carboxylate and the coordinating water molecules to form a one-dimensional diamond channel.In Ln-MOFs,each diamond channel is occupied by[?CH₃?₂NH₂]⁺cations to balance the negative charge of the framework.The compound 7 is a tetranuclear cluster of Dy,and the Dy cation uses eight carboxylate oxygen atoms and one nitrogen atom.Four Dy ions are connected to each other to form a triangular prism shape.Each cppc^2-anion connects two Dy?III?cations via two carboxylic acid groups to one pyridyl N atom to form a two-dimensional square mesh layer.3.Compounds 4 and 5 were found to have significant red and green fluorescence under UV light.At the same time,it was found that the Compounds 4 and 5 had obvious fluorescence quenching,including the pesticide pentachloronitrobenzene?PCNB?and the drug nitrofurazone?NTF?,and the quenching efficiency constant K_SVV was 8.99×10⁴?3?.and3.70×10⁴?4?.Compounds 4 and 5 are capable of quenching Fe³⁺?CrO₄^2-and Cr₂O₇^2-,and its are recognized by the naked eye.The detection limits for Fe³⁺?CrO₄^2-and Cr₂O₇^2-were2.25×10^-77 mol L^-1?4?,1.33×10^-77 mol L^-1?4?and 3.1×10^-66 mol L^-1?4?,respectively.Fluorescence analysis revealed that its quenching mechanism can be attributed to energy competition between the complex and the analyte.Compounds 4-7 is capable of adsorbing the cationic dye methylene blue?MLB?by ion exchange,and its adsorption rate can reach 92.1%.