A new ligand, N,N-BIS (6-metyl-2-pyridinecarboxylamide-N-oxide)-1,2-ethane (L) and six lanthanide(Ⅲ) complexes (RE=La, Sm, Eu, Tb, Gd, Yb) were synthesized and characterized in detail. The results indicated that the composition of the binary complexes was determined as [REL(H2O)(NO3)2]NO3·nH2O (n=0-2), and the Eu3+ complex had bright red fluorescence in solid state. Three complexes of Eu3+, Tb3+, and Gd3+ with 6-methylpicolinic acid N-oxide (L') were also synthesized. The relative intensity of sensitized luminescence for Eu3+ increased in the following order: L>L'. The phosphorescence spectra of the Gd3+ complexes at 77 K were measured. The energies of excited triplet state for the ligands were 20704 cm-1 (L) and 20408 cm-1 (L'). The facts that the ligands sensitized Eu3+ strongly and the order of the emission intensity for Eu3+ complexes were explained by ΔE(T-5D). This meant that the triplet energy level of the ligand was the main factor to influence RE3+ luminescence.
The crystal structure of cryptand L was determined via X-ray diffraction analysis.Four solid(cryptates) of cryptand(L) with M(Ⅲ) nitrates(M=Sm,Eu,Tb,Dy) were prepared and characterized by means of fluorescence spectroscopy.The fluorescence properties of those complexes show that all the cryptates have stronger luminescence intensity.That the complex of Eu(Ⅲ) has the strongest luminescence intensity(among) them shows that the cryptand′s triplet state energy matches with the vibration energy level of Eu(Ⅲ).The difference between fluorescence intensities of L cryptates and other series of cryptates implies that the (energy) transfer from L is more effective in fluorescence and antenna when L has a more flexibility structure.
