Structures and luminescent properties of two Tb(III) coordination polymers with aromatic dicarboxylates

Abstract

Two Tb(III) coordination polymers with ligands of two kinds of dicarboxylates were synthesized under hydrothermal conditions. The molecular formulas of the complexes were as follows: {[Tb2(3,5-pdc)(3,4-pdc)2(H2O)4]·2H2O}n (1) and [Tb(1,4-bdc)0.5(3,4-pdc)(H2O)2]n (2) (3,5-H2pdc = 3,5-pyridinedicarboxylic acid; 3,4-H2pdc = 3,4-pyridinedicarboxylic acid; 1,4-H2bdc = 1,4-benzenedicarboxylic acid). The two complexes were characterized by elemental analyses and IR spectra. And the structures of the two complexes were tested by X-ray single crystal diffraction. The crystal structures show 3,4-pdc coordinated with Tb(III) by oxygen atoms on the carboxyl groups. They connected the lanthanide ions to form 1D chain or 2D layer. 3,5-Pdc and 1,4-bdc ligands were both connectors in the complexes. They connected the 1D chain or 2D layer to further form 2D layer or 3D framework. The complexes emitted the green characteristic fluorescence of Tb(III) with the excitations of UV-rays. The absolute quantum yields (Фabs) of luminescence for the two Tb(III) complexes were also tested and the values of Фabs (1) and Фabs (2) were 42% (λex = 297 nm) and 53% (λex = 295 nm), respectively. The testing results of fluorescence lifetime showed the 5D4 excited states for the two complexes all had long lifetime and they were 0.819 and 0.901 ms, respectively.