abstract
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.
keywords
RARE-EARTH IONS; SPECTROSCOPIC PROPERTIES; LANTHANIDE COMPLEXES; EMISSION-SPECTRUM; 1,10-PHENANTHROLINE; LUMINESCENCE; CYCLODEXTRIN; SULFOXIDE); PARAMETERS; ADDUCTS
subject category
Optics
authors
Fernandes, JA; Ferreira, RAS; Pillinger, M; Carlos, LD; Jepsen, J; Hazell, A; Ribeiro-Claro, P; Goncalves, IS
our authors
Isabel Maria de Sousa Gonçalves
Associate Professor
José Alberto Pires Fernandes
Post-doc Fellowship
Luís Carlos
Full professor
Maria Rute de Amorim e Sá Ferreira André
Full professor
Martyn Pillinger
Principal Researcher