Synthesis, characterization and luminescent property of metal-ion-doped terbium complexes of 2,3-Pyrazinedicarboxylate

Using 2,3-pyrazine dicarboxylate (pzdc2−) as ligand, a series of new terbium complexes Tb2L2(HL)(NO3)radical dot10 H2O, Tb2Mg2L4(HL)(NO3)radical dot14 H2O, Tb2Ca2L4(HL)(NO3)radical dot14 H2O, Tb2Sr2L4(HL)(NO3)radical dot14 H2O, Tb2Ba2L4(HL)(NO3)radical dot14 H2O, Tb2Cd2L4(HL)(NO3)radical dot14 H2O, Tb2Co2L4(HL)(NO3)radical dot14 H2O, Tb2Ni2L4(HL)(NO3)radical dot14 H2O and Tb2Zn2L4(HL)(NO3)radical dot14 H2O (L=pzdc2-) have been synthesized. The complexes were characterized by elemental analysis, ICP-AES, molar conductivity measurement, TG-DSC analysis, IR spectroscopy and UV absorption spectroscopy. The luminescence spectra, luminescence lifetimes and emission quantum efficiencies of the complexes were measured. The results show that doping alkaline earth metal ions have significantly increased the luminescence intensities and quantum efficiencies of the complexes, and the sequence of the quantum efficiencies of the doped complexes is Ba2+>Ca2+>Mg2+>Sr2+. The enhancement of luminescence efficiencies may result from the decrease of the concentration quenching effect of Tb3+ ions, intramolecular energy transfer from the ligands coordinated with doped ions to Tb3+ ions and the lattice distortion of the complexes. The luminescence efficiencies of the Tb3+ ions are also enhanced by doping Cd2+ and Zn2+ ions. However, the complexes doped with Co2+ or Ni2+ ions exhibit luminescence quenching, which is caused by the energy consumed by these two ions in the form of d-d electron transitions.