Red (Eu3+), Green (Tb3+) and Ultraviolet (Gd3+) Emitting Nitrilotriacetate Complexes Prepared by One-step Synthesis

The [RE(NTA)(H2O)(2)]-(H2O) rare-earth complexes (RE3+: Eu, Gd, Tb and NTA: nitrilotriacetate) were synthesized and characterized by elemental analysis, thermogravimetry, X-ray diffraction, and infrared spectroscopy. The complexes show high crystallinity and thermostability. The photoluminescence behavior was studied based on the excitation and emission spectra, and luminescence decay curves. The compounds exhibit red (Eu3+), green (Tb3+) and UV (Gd3+) monochromatic emissions under UV excitation. The NTA ligand acts as luminescence sensitizer in the ligand-toRE(3+) intramolecular energy transfer process, owing to the fact that the first excited triplet state (Ti : 29 000 cm(-1)) is located above of the D-5(0) (Eu3+) and D-5(4) (Tb3+) emitting levels. The experimental intensity parameters ohm(lambda) (lambda : 2 and 4) for the Eu3+ NTA complex were calculated, and the results are discussed. The Gd3+ -NTA complex exhibits a high-intensity emission band in the UV region (32 000 cm(-1)) assigned to the P-6(7/2) -> S-8(7/2) intraconfigurational transition.