Structures and Luminescent Properties of Eu(III) and Tb(III) Complexes with a Pentacarboxylic Acid

Two 2D coordination polymers {[Eu-4(HL)(2)(ox)(2)(H2O)(10)]center dot 3H(2)O}(n) (1) and {[Tb-2(HL)(ox)(H2O)(5)]center dot 2H(2)O}(n) (2) (H5L=4-(4-carboxyphenyl)-pyridine-2,3,5,6-tetracarboxylic acid; ox=oxalate) were synthesized by using europium or terbium perchlorate to react with a new organic penta-carboxylic acids under hydrothermal condition. Single crystal X-ray diffraction structure analyses show that the two complexes are isomorphic and crystallize in monoclinic crystal system, P2(1)/c space group. The oxalate anions were formed perhaps by the decomposition of part of the ligands. A 2D layer is constructed by europium or terbium ions, oxalate anions and HL ligands. Both the complexes emitted the characteristic fluorescence of Eu(III) or Tb(III). The absolute quantum yields of the luminescence for 1 and 2 were 45% and 38%, respectively. The fluorescence lifetimes of D-5(0) excited state for 1 and D-5(4) excited state for 2 were also tested and the values were 1.83 and 1.07 ms, respectively.