Synthesis,Structure And Properties Of Complexes Based On Rare Earth Metal And Dipicolinic Acid

With the rapid development of supramolecular chemistry and crystal engineering,the synthesis of crystal materials by means of inorganic synthesis and preparation chemistry has attracted extensive attention.It also provides a new method and thought for the research of new rare earth functional materials.Compared with other metals,rare earth metals have flexible coordination number(8-12)and coordination mode in coordination process.Different rare earth metals have different 4f electrons,showing widely different chemical properties from the main group metals and d-zone elements,and showing considerable application prospects in optical,electricity,magnetism,organic catalytic transformation and biomedical materials.Rare earth ions are more likely to coordinate with common oxygen-containing and nitrogen-containing ligands.According to lewis acid-base theory,rare earth is a hard acid,so it tends to coordinate with oxygen-containing ligands.The common oxygen-containing ligands are organic carboxylic acids.The 2,6-pyridine dicarboxylic acid containing both O-and N-ligand atoms has a prominent bridging effect in the construction of rare earth-organic frameworks hybrid complexes due to its rigidity and planar nature,as well as its ability to form hydrogen bonds through carboxyl groups.In this paper,we represent the mild hydrothermal successfullysyntheses of three new kinds of organo-inorganic hybrid complexes of rare earth metals and transition metal copper with 2,6-pyridine dicarboxylic acid as the organic ligand and introducing 1,10-phenanthroline,which is the first innovation point.On the basis of the above works,the organic ligand1,10-phenanthrolinewas replaced by heteropoly acid with electron-storing capacity,and four new rare earth hybrid complexes containing pyridine carboxylic acid and organic heteropoly acid were successfully synthesized.Their properties and applications are explored by studying their structures.This is the second innovation point in this paper.The specific research results are as follows:1.2,6-pyridinedicarboxylic acid and 1,10-phenanthroline were selected as organic acid ligand.The introduction of rare earth ions and Cu I,successfully synthesized a series of new structure of 2D Cu(?)-Ln(?)heterometallic MOFs[Ln(pydc)₃Cu₂(phen)₄]·I(Ln=La(1),Nd(2),Dy(3);pydc=2,6-pyridine dicarboxylic acid;phen=1,10-phenanthroline)?The[Ln(pydc)₃]assembly with[Cu(phen)₂]units to construct a dodenuclear cluster via Cu-O bonds and?…?interaction.The clusters are further stacked into a 3D supramolecular framework with nano-sized cavities.Electrochemical analysis showed thatthe shape of CV curves can almost be retained,indicating the good stability of the electrochemical process.2.TwonovelrareearthMOF(metal-organicframework)[Ln(pydc)(H₂O)₄]₄Si W₁₂O₄₀·x H₂O(Ln=Pr(1),Nd(2);x=4.51,4.64)were synthesized by using tri-vacancy silicotungstic acid as inorganic-template and 2,6-pyridine dicarboxylic acid as organic multidentate ligands and adding rare-earth neodymium or praseodymium salt under hydrothermal condition.The compounds are isostructural,and each possesses a 3D zeolite-like cationic framework with the GIS(Gismondine)topology.The typical Keggin-anions[Si W₁₂O₄₀]^4-are located in the nano-sized cages through electrostatic interaction and strong hydrogen bonding interaction.Magnetic measurements of compound 2show the presence of a small anisotropy of the Nd(III)ions.Fluorescence analysis shows that the fluorescence of two compounds are produced by ligands,which may be caused by charge transfer transition from metals to ligands.3.Two novel POM-based TM-RE(POM=polyoxometalate,TM=transition-metal,RE=rare?earth)compounds[Ln(NH₄)(H₂O)₉][Cu(pydc)(H₂O)]₃[Si W₁₂O₄₀]·15H₂O(Ln=Nd(6),Sm(7))were synthesized by adding copper nitrate,rare earth neodymium or samarium salts,respectively,using silicotungstic acid hydrate as inorganic-template and 2,6-pyridine dicarboxylic acid as organic multidentate ligands under hydrothermal condition.Rare earth ions as counter ionsare linked with silicotungstic anion byelectrostatic interaction.Under the template effect of Keggin silicotungstic anion,the rare five-coordination mode of copper ions exists instead of the common six-coordination mode under the prevention of the larger steric hindrance of silicotungstic anion.Photocatalytic analysis showed that the two compounds have certain catalytic degradation capacity.