[Synthesis, characterization and fluorescence properties of rare earth complexes RE(TPTZ) Cl3]

The reaction of 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ) with RECl3 in ethanol solution was studied. Seven solid coordination compounds of rare earth were synthesized. Their elemental analysis, rare earth complexometric titration, molar conduction, TG-DTA curve, IR spectra and UV spectra were studied. The results suggest that the composition of the complexes was RE(TPTZ)C13 x 3H2O(RE = Sm, Eu, Tb, Dy) and Tb0.5Ln0.5 (TPTZ)Cl3 x 3H2O(Ln = Gd, Y, La), where TPTZ acts as a tridentate ligand with rare earth ion, the rare earth ion is eight-coordinate being bonded to the tridentate TPTZ, two Cl- anions and three water molecules, and the complexes-bounded may be [RE(TPTZ) (H2O)3Cl2] x Cl and [(Tb0.5 Ln0.5) (TPTZ) (H2O)3Cl2] x Cl. They are all 1 : 1 electrolytes in the DMF. The fluorescence spectra of the complexes were determined at room temperature. The results show that the fluorescence intensity of Tb3+ complex is the strongest among the four (Eu3+, Sm3+, Tb3+ and Dy3+) complexes. The lowest excitation state energy level of Tb3+ ion and the triplet state energy level of the ligand (TPTZ) match well. The absorbing energy of the ligand is effectively transferred to Tb3+ ion. The fluorescence intensity of terbium doped complexes (Tb3+ mixed by Gd3+, Y2+ and La3+) is stronger than that of terbium complex, showing that the fluorescence intensity of Tb3+ ion is raised by Gd3+, Y3+ and La3+ ions.