resumo
In this paper we report the synthesis of two new complexes, [Eu(fod)(3)(phen)] and [Tb(fod)(3)(phen)] (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadionate and phen = 1,10-phenanthroline), and their complete characterization, including single-crystal X-ray diffraction, UV-vis spectroscopy, IR spectroscopy, and TGA. The complexes were studied in detail via both theoretical and experimental approaches to the photophysical properties. The [Eu(fod)(3)(phen)] complex crystallizes in the monoclinic space group P2(1)/c. The crystal structure of [Eu(fod)(3)(phen)] exhibits an offset pi-pi stacking interaction between the phenanthroline ligands of adjacent lanthanide complexes. The Eu3+ cation is coordinated to three fod anionic ligands and to one phen. The symmetry around Eu3+ is best described as a highly distorted square antiprism. The molar absorption coefficients of [Eu(fod)(3)(phen)] and [Tb(fod)(3)(phen)] revealed an improved ability to absorb light in comparison with the stand-alone phen and fod molecules. [Tb(fod)(3)(phen)] emits weak UV excitation, with this feature being explained by the triplet-D-5(4) resonance, which contributes significantly to the nonradiative deactivation of Tb3+, causing a short lifetime and low quantum yield. The intensity parameters (Omega(2), Omega(4), and Omega(6)) of [Eu(fod)(3)(phen)] were calculated for the X-ray and Sparkle/AM1 structures and compared with values obtained for [Eu(fod)(3)(H2O)(2)] and [Eu(fod)(3)(phen-N-O)] (phen-N-O = 1,10-phenanthroline N-oxide) samples. Intensity parameters were used to predict the radiative decay rate. The theoretical quantum efficiencies from the X-ray and Sparkle/AM1 structures are in good agreement with the experimental values, clearly attesting to the efficacy of the theoretical models.
palavras-chave
RARE-EARTH IONS; LUMINESCENCE QUANTUM YIELD; NUCLEAR MAGNETIC-RESONANCE; 2D COORDINATION POLYMERS; BETA-DIKETONE COMPLEXES; ENERGY-TRANSFER PROCESS; SPARKLE MODEL; INTENSITY PARAMETERS; EUROPIUM COMPLEX; METAL-COMPLEXES
categoria
Chemistry; Physics
autores
dos Santos, ER; Freire, RO; da Costa, NB; Paz, FAA; de Simone, CA; Junior, SA; Araujo, AAS; Nunes, LAO; de Mesquita, ME; Rodrigues, MO
nossos autores
Filipe Alexandre Almeida Paz
Investigador Principalagradecimentos
We appreciate the financial support from CNPq and CAPES (Brazilian agencies) and RENAMI (Brazilian Molecular and Interfaces Nanotechnology Network). We also thank the FCT (Fundacao para a Ciencia e a Tecnologia, Portugal) for financial support (Grant PTDC/QUI-QUI/098098/2008).