Investigation of europium(III) and gadolinium(III) complexes with naphthoyltrifluoroacetone and bidentate heterocyclic amines


Lewis base adducts of the type Ln(NTA)(3) . phen and the binuclear complexes [ln(NTA)(3)](2) . bbym [NTA = 1-(2-naphthoyl)-3,3,3-trifluoroacetone, phen=1,10-phenanthroline, bpym . 2.2'-bipyrimidine: Ln, Eu, Gd] have been prepared by replacement of the coordinated water molecules in the complexes Ln(NTA) . 2H(2)O. The compounds were characterised by elemental analysis, H-1 NMR. X-ray diffraction (XRD), therniogravinietric analysis, FTIR and FT Raman spectroscopy, and photoluminescence (PL) spectroscopy. For both new bands were observed in the Raman spectra in the low-wavenumber region (100-600cm(-1)), assigned to Ln-N stretching vibrations (in agreement with ab initio calculations). The crystal structures of the Eu-III complexes were determined by single crystal XRD, In both complexes the coordination polyhedra can be regarded as square antiprisms. distorted towards a bicapped trigonal prism for the mononuclear complex and towards a dodecahedron for the binuclear complex. A Eu Eu distance or 6.856 angstrom was found for the latter. Powder XRD indicates that the corresponding gadolinium(III) compound has a similar structure. The room temperature PL spectra of the europium complexes in the solid state present a series of sharp lines assigned to D-5(0) -> F-7(04) transitions. No emission from the organic part of the compounds is observed, indicating that energy transfer from the ligands to the Eu3+ ion is quite efficient, A number of parameters were determined from the PL spectra, including estimates for the overall crystal field strengths, and D-5(0) lifetimes and quantum efficiencies. The PL spectra for ethanol solutions of the Eu complexes confirm that the NTA and N-ligands remain attached. Slight changes in the PL data upon solubilisation are attributed to an interaction of solvent molecules with the metal centres. (c) 2004 Elsevier B.V. All rights reserved.



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Fernandes, JA; Ferreira, RAS; Pillinger, M; Carlos, LD; Jepsen, J; Hazell, A; Ribeiro-Claro, P; Goncalves, IS

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