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The complexes [Eu(12-crown-4)(terpy)(H2O)]3Cl, [Eu(15-crown-5)(terpy)]3Cl, [Tb(12-crown-4)(terpy)(H2O)]3Cl, [Tb(15-crown-5)(terpy)]3Cl, [Gd(12-crown-4)(terpy)(H2O)]3Cl and [Gd(15-crown-5)(terpy)]3Cl (terpy = 2,2′,6′,2′′-terpyridine) were synthesized and characterized by CHN elemental analysis, infrared spectroscopy and fluorescence spectroscopy. Emission spectra were obtained on both, solid state and aqueous solutions for europium and terbium complexes. The complexes exhibit good emission, even in aqueous solution, enhancing their potential for biological applications. The reduction of emission intensity, from solid state to aqueous solution, is lower for europium complexes, in comparison to terbium complexes. The [Eu(12-crown-4)(terpy)(H2O)] · 3Cl complex exhibits an emission lifetime of 0.64 ms while [Eu(15-crown-5)(terpy)] · 3Cl exhibits a value of 0.38 ms. Furthermore, the 15-crown-5 complex emission intensity is about 3.8 times larger than the emission intensity of the 12-crown-4 complex. This ratio (3.8) is the same as observed for the ARAD and ANRAD for the aqueous solutions: 1225.5/339.5 = 3.6. The aqueous solution quantum yield is higher for [Eu(12-crown-4)(terpy)(H2O)]3Cl in comparison with [Eu(15-crown-5)(terpy)]3Cl, suggesting that 12-crown-4 exhibits a more suitable ratio than 15-crown-5. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and photoluminescent properties of Ln(III)–thenoyltrifluoroacetonate and dibenzoylmethanate complexes (Ln=Eu(III) and Gd(III) ions) containing tertiary amides such as dimethylacetamide (DMA), dimethylformamide (DMF), and dimethylbenzamide (DMB) as neutral ligands are reported. The Ln complexes were characterized by elemental analysis, complexometric titration with EDTA, and infrared spectroscopy. Single-crystal X-ray structure data of the [Eu(DBM)3·(DMA)] compound indicates that this complex crystallizes in the triclinic system, space group with the following cell parameters: a =10.2580(3)Å, b =10.3843(2)Å, c =22.3517(5)Å, α =78.906(2)°, β =78.049(2)°, λ =63.239(2)°, V =2066.41(9)Å3, and Z =2. The coordination polyhedron for the Eu(III) complex may be described as an approximate C2v distorted monocapped trigonal prism. The optical properties of the Eu(III) complexes were studied based on the intensity parameters and luminescence quantum yield (q). The values of the Ω 2 parameter of the Eu–DBM complexes are larger than those for the Eu–TTA complexes, indicating that the Eu(III) ion is in a more polarizable chemical environment in the former case. The geometries of the complexes have been optimized by using the Sparkle Model, and the results have been used to perform theoretical predictions of the ligand-to-metal energy transfer via direct and exchange Coulomb mechanisms. [Copyright &y& Elsevier]

Abstract: The complexes [Eu(12-crown-4)·phen2]·X3 (phen=1,10-phenanthroline; X=F, Cl, Br, SCN, ClO4 and NO3) were synthesized and characterized by elemental analysis, UV–vis and IR spectroscopy. A thermogravimetric study was performed to evaluate the effect of the counter-ion on the thermal degradation profile of the [Eu(12-crown-4)·phen2]+3 complex cation. In general, the 1,10-phenanthroline molecules are the first to be released, showing that the crown ether molecule forms more stable bonds with the +3 cation. The fluorine complex sublimes and thus could be employed as a precursor for preparation of luminescent films. [Copyright &y& Elsevier]

Abstract: In this work, it were performed computational design and synthesis of a new luminescent Eu(III) complex with the usual 1,10-phenanthroline ligand substituted in the 4 and 7 positions by chlorine atoms, which one has shown a higher luminescent output than that of the non-substituted analogous complex. The molecular structures for all complexes using the Sparkle and DFT methods were obtained, such as their coordination bond distances with values in a typical range. Analyzing the direct Eu(III) ion excitation for the phenCl complex, all of them are red shifted in comparison to the one of the phen complex suggesting that the ion environment is more polarizable in the first case, this corroborate with results obtained for intensities and R02 parameters. [Copyright &y& Elsevier]

Abstract: Europium complexes presenting general formulas [Eu(ACIND)3(H2O)2] and [Eu(ACIND)3(TPPO)2] have been synthesized and characterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)3(H2O)(EtOH)] complex was also prepared and its structure determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P21/n with the water molecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the oxygen donor atoms with a site of symmetry close to C 2ν . Isovaleryl groups in the ISOVIND molecules in the structure are disordered over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photoluminescence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-to-metal intramolecular energy transfer process. [Copyright &y& Elsevier]

In the present work, we sought to improve our sparkle model for the calculation of lanthanide complexes, SMLC, in various ways: (i) inclusion of the europium atomic mass, (ii) reparametrization of the model within AM1 from a new response function including all distances of the coordination polyhedron for tris(acetylacetonate)(1,10-phenanthroline) europium(Ill), (iii) implementation of the model in the software package MOPAC93r2, and (iv) inclusion of spherical Gaussian functions in the expression which computes the core-core repulsion energy. The parametrization results indicate that SMLC II is superior to the previous version of the model because Gaussian functions proved essential if one requires a better description of the geometries of the complexes. In order to validate our parametrization, we carried out calculations on 96 europium(III) complexes, selected from Cambridge Structural Database 2003, and compared our predicted ground state geometries with the experimental ones. Our results show that this new parametrization of the SMLC model, with the inclusion of spherical Gaussian functions in the core-core repulsion energy, is better capable of predicting the Eu-ligand distances than the previous version. The unsigned mean error for all interatomic distances Eu-L, in all 96 complexes, which, for the original SMLC is 0.3564 Å, is lowered to 0.1993 Å when the model was parametrized with the inclusion of two Gaussian functions. Our results also indicate that this model is more applicable to europium complexes with β-diketone ligands. As such, we conclude that this improved model can be considered a powerful tool for the study of lanthanide complexes and their applications, such as the modeling of light conversion molecular devices. [ABSTRACT FROM AUTHOR]

By using (3-glycidoxypropyl) trimethosysilane (GPTMS) and (3-trimethoxysilylpropyl) ethylenediamine (TSPED) as precursors, transparent self-standing films doped with the luminescent complexes Eu(hfc)3 · bipy and Eu(hfc)3 · terpy were prepared. The doped films were so studied from a spectroscopic point of view. It is verified that the film composition exerts effects on both, the intensity and lifetime of the emission process. For the GPTMS and TSPED films the measured lifetimes gave the values 250 and 183 μs respectively, for the complex Eu(hfc)3 · terpy. The TSPED matrix provides emissions with higher intensities, but lower lifetimes. For the GPTMS films an opposite behavior is observed. Comparing the emission spectra for GPTMS films doped with the complexes Eu(hfc)3bipy and Eu(hfc)3terpy, it is verified that not only the chemical composition of GPTMS or the type of ligand involved in the complex, but also the symmetry of the complex used as dopant, will be of prominent importance to the spectroscopic properties of the obtained doped films. [Copyright &y& Elsevier]

By using (3-trimethoxysilylpropyl) ethylenediamine (TSPED) and a dental material (acrylic resin) as precursors, self-standing films doped with the luminescent complexes Eu(fod)3·2H2O and Eu(fod)3·terpy were prepared. The doped films were so studied from a spectroscopic point of view. Is verified that the film composition exerts remarkable effects on both, the intensity and lifetime of the emission process. Acrylic resin films reduces the intensity of the emission process, but increases the lifetime of a such process, in comparison with TSPED films, for which an opposite behavior is observed. The measured lifetimes for the emission process for the compounds Eu(fod)3·2H2O in TSPED and acrylic resin films are 306 and 369 μs, respectively. For the same film matrices, the measured lifetimes for the complex Eu(fod)3·terpy gave the values 347 and 880 μs, respectively. [ABSTRACT FROM AUTHOR]