Crystal structure and fluorescence property of lanthanide coordination polymer {[Eu (2, 5-PDA) (OAc) (H2O)]·1.5H2O}n

The europium coordination polymer [Eu (PDA) (OAc) (H2O)]n·1.5nH2O (PDA=2, 5-pyri-dinedicarboxylate, OAc=acetate) was synthesized by hydrothermal method, and characterized by single crystal X-ray diffraction and elemental analysis. The crystallographic data show that the complex crystallizes in a monoclinic system, space group P21/n, cell parameters a=0.93501 (15) nm, b=0.83477 (13) nm, c=1.6779 (3) nm, β=106.18°, V=1.2578 (3) nm3, Z=4, the final indentical factors [I > 2σ (I)]:R1=0.0243, wR2=0.0605. One carboxyl group of PDA ligand and OAc ligand links two europium (III) ions of two asymmetric units to form a dinuclear unit, while PDA ligands join dinuclear units from two directions, which are 88° and 56° dihedral angles with acetate ligands, respectively. Along the α-axis, a three-dimensional structure constructed by coordinated bonds is thus formed by PDA and OAc ligands, in which uncoordinated water molecules exist in the crystal via hydrogen bonds with coordinated water molecules. The photoluminescence property of the title compound was also investigated. The intensity ratio I (5D0-> F2/5D0-> 7F1) is ca. 1.44, which indicates that the Eu (III) ion in the title compound is not located at the center of inversion.