Synthesis, Crystal Structure And Thermal Dynamics Analysis Of Rare Earth Coordination Polymer Of Carboxylic Acids

Because of a considerable benefit and good application prospect in catalysis, fluorescence,adsorption and separation, magnetic, biology and pharmacology and so on, coordinationpolymer research is increasingly becoming the hot spot. Rare earth elements are different frommain group and other subgroup elements in the chemical properties. They have their owncharacteristics. These properties create a unique rare earth organic chemistry. In the synthesisprocess of the complexes, due to structure stability of the rigid carboxylic acid ligand, it iseasy to form microporous structure, we can construct basic rigid structure of the complexes.Flexible carboxylic acid ligands are easy to bend and can make up the deficiency of the rigidcarboxylic acid ligands. In this paper, a serie of rare earth coordination polymers wereobtained based on rigid ligands pyridine-2,5-dicarboxylic acid (H2pydc), isophthalic acid(m-H2bdc) and flexible ligand glutaric acid.Nine new lanthanide complexes were obtained by the hydrothennal reactions. They are{[Ce4(m-bdc)6(H2O)5]·H2O}n(1),{[Ce2(m-bdc)3(H2O)2]}n(2),{[Nd2(m-bdc)3(H2O)2]}n(3),{H2[Tb(pydc)2]}n(4),{[Sm(pydc)2(H2O)5]·4H2O}n(5),{[Dy(pydc)2(H2O)5]·4H2O}n(6),{[Dy2(C5H6O4)3(H2O)2]·4H2O}n(7),{[Yb2(C5H6O4)3(H2O)2]·4H2O}n(8) and {[CO][Nd2(CO)(pydc)2(C5H6O4)]·2H2O}n (9),(C5H6O4=glutaconate,bdc=benzeneicarboxylatedianions, pydc=2,5-pyridinedicarboxylic acid). The conditions of synthesis and the single single-crystal X-raydiffraction results are as follows:(1) The complex{[Ce4(m-bdc)6(H2O)5]·H2O}n(1) was obtained in pH=5~6and mixingsixty minutes, then heated at160℃for72hours under autogenous pressure. The complex1based on rigid carboxylic acid m-H2bdc as ligands. The single crystal structures reveals thatthe complex1belongs to monoclinic, space group P21/c. It has two-dimensional structuresand four central ion, the coordination number of central ion Ln1(Ⅲ) is seven. Ln1(Ⅲ) ionpresent a pentagonal bipyramid coordination geometry. The coordination number of centralion Ln2(Ⅲ) is eight. Ln2(Ⅲ) ion present a dodecahedron coordination geometry. thecoordination number of central ion Ln3(Ⅲ) and Ln4(Ⅲ) are both nine. They present adistorted three cap triprism coordination geometry. (2) The complexes {[Ce2(m-bdc)3(H2O)2]}n(2) and {[Nd2(m-bdc)3(H2O)2]}n(3) wereobtainned in pH=5~6and heated at160℃for72hours under autogenous pressure. They basedon rigid carboxylic acid m-H2bdc as ligands. The single crystal structures reveals that the twocomplexes are isomorphic and belong to monoclinic, space group P21/c. They havetwo-dimensional structures and two central ion. The coordination number of central ionLn1(Ⅲ) is seven, it present a pentagonal bipyramid coordination geometry. The coordinationnumber of central ion Ln2(Ⅲ) is eight, it present a dodecahedron coordination geometry.(3) The complex {H2[Tb(pydc)2]}n(4) was obtained in pH=6~7and mixing thirtyminutes, then heated at170℃for96hours under autogenous pressure. The complex4basedon rigid carboxylic acid H2pydc as ligands. The single crystal structures reveals that thecomplex4belongs to Orthorhombic, space group Pbcn. It has three-dimensional structuresand one central ion. The coordination number of central ion is eight. The central ion presents adodecahedron coordination geometry. The complex4exhibits intense luminescence in theliquid state at room temperature.(4) The complexes {[Sm(pydc)2(H2O)5]·4H2O}n(5) and {[Dy(pydc)2(H2O)5]·4H2O}n(6)were obtained in pH=6~7and heated at170℃for96hours under autogenous pressure. Theybased on rigid carboxylic acid H2pydc as ligands. The single crystal structures reveals that thetwo complexes are isomorphic and belong to monoclinic, space group C2/c. They havezero-dimensional structures and one central ion. The coordination number of central ion areboth nine. They present a three cap tri-prism coordination geometry.(5) The complexes {[Dy2(C5H6O4)3(H2O)2]·4H2O}n(7) and {[Yb2(C5H6O4)3(H2O)2]·4H2O}n(8) were obtained in pH=5~6and heated at160℃for72hours under autogenous pressure.They based on flexible carboxylic acid glutaric acid as ligands. The single crystal structuresreveals that the two complexes are isomorphic and belong to monoclinic, space group C2/c.They have three-dimensional structures and one central ion. The coordination number ofcentral ion are both nine. They present a distorted three cap triprism coordination geometry.(6) The complex{[CO][Nd2(CO)(pydc)2(C5H6O4)]·2H2O}n(9) was obtained in pH=6~7and mixing sixty minutes, then heated at180℃for120hours under autogenous pressure. Itbased on rigid and flexible (H2pydc and glutaric acid) carboxylic acid as ligands. The singlecrystal structures reveals that the complex belongs to Triclinic, space group P-1. It hasthree-dimensional structures and two central ion. The coordination number of central ion Ln1(Ⅲ) and Ln2(Ⅲ) are both nine. They present a three cap triprism coordination geometry.Their structure have been measured by single crystal diffraction instrument. Physical andchemical properties have been characterized by elemental analysis, thermal analyses, IR spectra and Fluorescence. In addition, we analyze thermal stability and dynamics of thecomplexes and get pyrolysis kinetic parameters.