title: Theoretical and experimental spectroscopic approach of fluorinated Ln(3+)-beta-diketonate complexes.
abstract: 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 Eu(3+) cation is coordinated to three fod anionic ligands and to one phen. The symmetry around Eu(3+) 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-(5)D(4) resonance, which contributes significantly to the nonradiative deactivation of Tb(3+), 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)(H(2)O)(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.
authors.affiliation: Department of Chemistry, UFS, 49100-000 Sao Cristovao, SE, Brazil.
authors.forename: Edjane R
authors.initials: ER
authors.lastname: Dos Santos
authors.forename: Ricardo O
authors.initials: RO
authors.lastname: Freire
authors.forename: Nivan B
authors.initials: NB
authors.lastname: da Costa
authors.forename: Filipe A Almeida
authors.initials: FA
authors.lastname: Paz
authors.forename: Carlos A
authors.initials: CA
authors.lastname: de Simone
authors.forename: Severino A
authors.initials: SA
authors.lastname: Júnior
authors.forename: Adriano A S
authors.initials: AA
authors.lastname: Araújo
authors.forename: Luiz Antônio O
authors.initials: LA
authors.lastname: Nunes
authors.forename: Maria E
authors.initials: ME
authors.lastname: de Mesquita
authors.forename: Marcelo O
authors.initials: MO
authors.lastname: Rodrigues