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Z. Naturforsch. 2014,
69b, 231 – 238
doi:10.5560/ZNB.2014-3263
Red (Eu3+), Green (Tb3+) and Ultraviolet (Gd3+) Emitting Nitrilotriacetate Complexes Prepared by One-step Synthesis
1 Departamento de Química Fundamental, Instituto de Química da Universidade de São Paulo, 05508-900, São Paulo, SP, Brazil
2 Instituto de Pesquisas Energéticas e Nucleares, IPEN, Cidade Universitária, 05508-000, São Paulo, SP, Brazil
3 Department of Physics, CICECO, University of Aveiro, Campus, Universitário de Santiago, 3810–193, Aveiro, Portugal
4 Departamento de Química Fundamental, CCEN, Universidade Federal da Pernambuco, 50670-901, Recife, PE, Brazil
Reprint requests to H. F. Brito. Phone: +55-11-3091-3708. E-mail:
hefbrito@iq.usp.br
Received September 11, 2013 / published online February 17, 2014
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-to-RE3+ intramolecular energy transfer process, owing to the fact that the first excited triplet state (T1: 29000 cm−1) is located
above of the 5D0 (Eu3+) and 5D4 (Tb3+) emitting levels. The experimental intensity parameters Ωλ (λ: 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 (32000 cm−1) assigned to the 6P7/2 → 8S7/2 intraconfigurational transition.
Key words: Rare-Earth Complexes, Tricarboxylates, Synthesis, Intramolecular Energy Transfer, Photoluminescence