Synthesis, Characterization and Luminescence Properties of Rare Earth Complexes with Bis(Pyridinyl-Amide)

A ligand, N1,N4-di（pyridin-2-yl）succinamide （L） and its lanthanide（Ⅲ） complexes （RE= La, Eu, Tb, Gd, Yb ） were synthesized and characterized in detail. The results indicate that the composition of the binary complexes is determined as [REL（H2O）2（NO3）2] NO3, that the complexes are 1∶1 electrolytes in DMF, and that the Tb 3+ complex has brightly green fluorescence in a solid state. At the same time, the energy levels of the excited triplet states for the six ligands were determined to be 22989 cm -1 . The fact that the ligand sensitize Tb 3+ complexes was explained by the relative energy gap between the lowest triplet energy level of the ligand （T） and 5DJ of Tb 3+ or Eu 3+ . When 2000 cm -1 <ΔE（T-5D4）<3000 cm -1 , the luminescent intensity of the Tb 3+ complex is stronger. When 3000 cm -1 <ΔE（T-5D1）, the luminescent intensity of the Eu 3+ complex is weaker or close to nil. This means that the triplet energy level of the ligand is a chief factor that dominates RE 3+ luminescence.