Synthesis, Structure And Properties Of Pyrimidine Carboxylic Acid Metal Complexes

Porous metal-organic framework complexes have potential applications in the fields of gas adsorption,catalysis,fluorescence and magnetism because of their unique topological structure.In this paper,nine kinds of rare earth metal complexes were synthesized by using pyrimidine-2-carboxylic acid(Hpmc)and 2-aminopyrimi-dine-4,6-dicarboxylic acid(H2apmc)as ligands respectively.The structure and properties of the complexes were characterized and analyzed by IR,X-ray single crystal diffraction,CD,TG and fluorescence analysis.The conclusions are as below:(1)Six lanthanide complexes[Ln(pmc)2NO3]n(1-2)(Hpmc = pyrimidine-2-carboxylic acid,Ln = La,Pr),[Ln(pmc)2(H2O)3]NO3·H2O(3-6)(Ln = Eu,Tb,Dy,Er)were synthesized by the reactions of lanthanide nitrate and pyrimidine-2-carboxylic acid in water at room temperature.Structure analysis shows that complexes 1-2are isostructural with P43212 space group,while isostructural complexes 3-6 belong to the P21/c space group.In complexes 1-2,the metal centers are coordinated by nitrates and pmc whichare self-assembled to construct a 3D porous networkwith 62.62.62.62.62.62(66)topology.While in complexes 3-6,H2O and pmc ligands are coordinated and the complexes exhibit a 1-dimensional zig-zag chain,which is further expanded into a3D structure by hydrogen bonding.In addition,the circular dichroism of 1-2 proves that the two complexes areboth chiral with achiral ligand of Hpmc.Luminescent measurements of compounds 3-5 indicate that the characteristic fluorescence of Eu3+,Tb3+ and Dy3+ are observed.(2)Three lanthanide complexes[Ln2(apmc)3(H2O)4]n(7-9)(H2apmc = 2-amino-pyrimidine-4,6-dicarboxylic acid,Ln = Sm,Tb,Ho)were synthesized by the reactions of lanthanide nitrate and K2apmc under hydrothermal conditions.X-ray diffraction shows that the complex 7 belongs to P-1 space group,while the complexes 8 and 9 are isomorphic,belonging to the C2/c space group.The complexes 7-9 have a two-dimensional network structure,which is further expanded into a 3D porous network structure under action of hydrogen bonds.The solid fluorescence results of the complexes 7 and 8 show that the fluorescence of the complexs belongs to the luminescence of lanthanide metal ions(Sm3+,Tb3+).