Ionic liquids as solvents for near-infrared emitting lanthanide complexes

It is shown that ionic liquids are promising solvents for near-infrared emitting lanthanide complexes, because ionic liquids are polar non-coordinating solvents that can solubilize lanthanide complexes. Neodymium(III) tosylate, bromide, triflate and sulfonylimide complexes were dissolved in 1-alkyl-3-methylimidazolium ionic liquids that contain the same anion as the neodymium(III) complexes. Near-infrared luminescence spectra of these neodymium(III) salts were measured by direct excitation of the neodymium(III) ion. The absorption spectra show detailed crystal-field fine structure and Judd-Ofelt parameters have been determined. Intense near-infrared luminescence was observed upon ligand excitation for neodymium(III) complexes with 1,10-phenanthroline or beta-diketonate ligands. (C) 2004 Elsevier B.V. All rights reserved.

Lanthanide luminescent logic gate mimics in soft matter: [H(+)] and [F(-)] dual-input device in a polymer gel with potential for selective component release

The non-covalent incorporation of responsive luminescent lanthanide, Ln(iii), complexes with orthogonal outputs from Eu(iii) and Tb(iii) in a gel matrix allows for in situ logic operation with colorimetric outputs. Herein, we report an exemplar system with two inputs ([H(+)] and [F(-)]) within a p(HEMA-co-MMA) polymer organogel acting as a dual-responsive device and identify future potential for such systems.

Persistent luminescence of SrAl2O4:Ce(III), Dy, Eu nanotubes, nanowires and core-shells for people with disabilities: nano-emergency

Este estudo transversal está focado na propriedade de luminescência persistente do aluminato de estrôncio co-dopado com cério (III), disprósio (III) e európio (II), SrAl2O4:Ce3+, Dy3+, Eu2+, em sistemas de sinalização de áreas de risco e emergências para pessoas com deficiências. Na área da ciência e engenharia dos materiais, foram desenvolvidos novos materiais com características nanométricas, nanotubos, nanoarames e nanobastões luminescentes de SrAl2O4:Ce3+, Dy3+, Eu2+ para aplicações na área da reabilitação e acessibilidade de pessoas com deficiências. Os nanotubos foram obtidos a partir de micro- e nano-partículas precursoras sintetizadas por reacção do estado-sólido e tratamento térmico de recozedura (1273-1473 K). Os nanoarames e nanobastões foram preparados por moagem, sonificação e recozedura (373 K). Novas nanocápsulas de aluminatos luminescentes dopados com cério (III) e encapsulados com TiO2 foram criadas de modo a obter-se materiais multifuncionais, designadamente com acção fotocatalítica antimicrobiana, antibacteriana e resistência à água. Tais aluminatos podem ser amplamente aplicados como superfícies higiénicas, auto-limpantes, em biomateriais, no domínio de medicamentos antibióticos, na formulação de vacinas, e com ênfase à aplicação em cerâmicas fotoluminescentes. As metodologias de obtenção de tais nanoestruturas de aluminato de estrôncio dopado com cério (III) e do seu encapsulamento, desenvolvidas no âmbito desta tese, são aplicáveis a diversos aluminatos dopados com outros iões lantanídeos (Ln consiste em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm ou Lu) com a fórmula M(1-x-y)N2O4:Cex, Lny, onde M é Be, Mg, Ca, Sr ou Ba. Na área da oftalmologia, foi desenvolvido um equipamento médico para o diagnóstico de biofuncionalidade das células retinais fotoreceptoras, e como suporte à telemedicina oftalmológica. Este equipamento foi utilizado para realizar testes de visão cromática FM100HUE em fundo branco/preto para a personalização de materiais luminescentes. Os resultados demonstraram uma biofuncionalidade celular à visibilidade fotópica das cores em fundo preto superior no grupo de tratamento, composto por pessoas com retinopatia diabética (n=38), em comparação ao grupo de referência (n=38). Estes resultados sugerem a recomendação de materiais com fotoluminescência persistente (λem=485-555 nm), incluindo SrAl2O4:Ce3+, Dy3+, Eu2+, para o referido grupo de tratamento, em sinalização de emergência e em ambientes de baixa iluminação. Na área da arquitectura, foi proposta uma nova aplicação dos referidos nanomateriais luminescentes à base de SrAl2O4:Ce3+, Dy3+, Eu2+ em cerâmica de revestimento, tendo em vista a sua boa visibilidade e uso por pessoas com deficiências. Novos pavimentos, cerâmicos, fotoluminescentes, foram desenhados com propriedades multisensoriais (contraste táctil, sonoro e visual) e antimicrobianas, para pessoas portadoras de deficiências utilizarem, no escuro, com a prioridade de salvar vidas em emergências. Tais pisos, com relevos, podem ser combinados de modo a compor um sistema exclusivo de sinalização fotoluminescente multisensorial que possibilita a rápida evacuação mediante o uso de auxílios de mobilidade (e.g. bengala, cadeira de rodas, andadores, muletas). A solução integrada de tais inovações que potencializa a propriedade de luminescência persistente de SrAl2O4:Ce3+, Dy3+, Eu2+ de modo acessível para as pessoas com deficiências, pode contribuir para salvar vidas, no escuro, em emergências.

A pyrophosphate-responsive gadolinium(III) MRI contrast agent

This study shows that the relaxivity and optical properties of functionalised lanthanide-DTPA-bis-amide complexes (lanthanide=Gd3+ and Eu3+, DTPA=diethylene triamine pentaacetic acid) can be successfully modulated by addition of specific anions, without direct Ln3+/anion coordination. Zinc(II)-dipicolylamine moieties, which are known to bind strongly to phosphates, were introduced in the amide “arms” of these ligands, and the interaction of the resulting Gd–Zn2 complexes with a range of anions was screened by using indicator displacement assays (IDAs). Considerable selectivity for polyphosphorylated species (such as pyrophosphate and adenosine-5′-triphosphate (ATP)) over a range of other anions (including monophosphorylated anions) was apparent. In addition, we show that pyrophosphate modulates the relaxivity of the gadolinium(III) complex, this modulation being sufficiently large to be observed in imaging experiments. To establish the binding mode of the pyrophosphate and gain insight into the origin of the relaxometric modulation, a series of studies including UV/Vis and emission spectroscopy, luminescence lifetime measurements in H2O and D2O, 17O and 31P NMR spectroscopy and nuclear magnetic resonance dispersion (NMRD) studies were carried out.

Separation of lanthanides and actinides(III) using tridentate benzimidazole, benzoxazole and benzothiazole ligands

The ability of new hydrophobic tridentate ligands based on 2,6-bis(benziinidazol-2-yl)pyridine, 2,6-bis(benzoxazol-2-yl)pyridine and 2,6-bis(benzothiazol-2-yl)pyridine to selectively extract americium(III) from europium(III) was measured. The most promising ligand-2,6-bis(benzoxazol-2-yl)-4-(2-decyl-1-tetradecyloxy)pyridine L-9 was found to give separation factors (SFAm/Eu) of up to 70 when used to extract cations from 0.02-0.10 M HNO3 into TPH in synergy with 2-bromodecanoic acid. Six structures of lanthanide complexes with 2,6-bis(benzoxazol-2-yl)pyridine L-6 were then determined to evaluate the types of species that are likely to be involved in the separation process. Three structural types were observed, namely [LnL(6)(NO3)(3)(H2O)2], 11-coordinate only for La, [LnL(6) (NO3)(3) (CH3CN)], 10-coordinate for Pr, Nd and Eu and [LnL(6) (NO3)(3)(H2O)], L 10-coordinate for Eu and Gd. Quantum Mechanics calculations were carried out on the tridentate ligands to elucidate the conformational preferences of the ligands in the free state and protonated and diprotonated forms and to assess the electronic properties of the ligands for comparison with other terdentate ligands used in lanthanide/actinide separation processes.

Solvent extraction and lanthanide complexation studies with new terdentate ligands containing two 1,3,5-triazine moieties

The extracting agent 2,6-bis(4,6-di-pivaloylamino-1,3,5-triazin-2-yl)-pyridine (L-5) in n-octanol was found, in synergy with 2-bromodecanoic acid, to give D-Am/D-Eu separation factors (SFs) between 2.4 and 3.7 when used to extract the metal ions from 0.02-0.12 M HNO3. Slightly higher SFs (4-6) were obtained in the absence of the synergist when the ligand was used to extract Am(III) and Eu(III) from 0.98 M HNO3. In order to investigate the possible nature of the extracted species crystal structures of L-5 and the complex formed between Yb(III) with 2,6-bis(4,6-di-amino-1,3,5-triazin-2-yl)-pyridine (L-4) were also determined. The structure of L-5 shows 3 methanol solvent molecules all of which form 2 or 3 hydrogen bonds with triazine nitrogen atoms, amide nitrogen or oxygen atoms, or pyridine nitrogen atoms. However, L-5 is relatively unstable in metal complexation reactions and loses amide groups to form the parent tetramine L-4. The crystal structure of Yb(L-4)(NO3)(3) shows ytterbium in a 9-coordinate environment being bonded to three donor atoms of the ligand and three bidentate nitrate ions. The solvent extraction properties of L-4 and L-5 are far inferior to those found for the 2,6-bis-(1,2,4-triazin-3-yl)-pyridines (L-1) which have SF values of ca. 140 and theoretical calculations have been made to compare the electronic properties of the ligands. The electronic charge distribution in L-4 and L-5 is similar to that found in other terdentate ligands such as terpyridine which have equally poor extraction properties and suggests that the unique properties of L-1 evolve from the presence of two adjacent nitrogen atoms in the triazine rings.

QSAR studies of multidentate nitrogen ligands used in lanthanide and actinide extraction processes

Quantitative structure activity relationships (QSARs) have been developed to optimise the choice of nitrogen heterocyclic molecules that can be used to separate the minor actinides such as americium(III) from europium(III) in the aqueous PUREX raffinate of nuclear waste. Experimental data on distribution coefficients and separation factors (SFs) for 47 such ligands have been obtained and show SF values ranging from 0.61 to 100. The ligands were divided into a training set of 36 molecules to develop the QSAR and a test set of 11 molecules to validate the QSAR. Over 1500 molecular descriptors were calculated for each heterocycle and the Genetic Algorithm was used to select the most appropriate for use in multiple regression equations. Equations were developed fitting the separation factors to 6-8 molecular descriptors which gave r(2) values of >0.8 for the training set and values of >0.7 for the test set, thus showing good predictive quality. The descriptors used in the equations were primarily electronic and steric. These equations can be used to predict the separation factors of nitrogen heterocycles not yet synthesised and/or tested and hence obtain the most efficient ligands for lanthanide and actinide separation. (C) 2003 Elsevier B.V. All rights reserved.

Complexes formed between the quadridentate, heterocyclic molecules 6,6 '-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2 '-bipyridine (BTBP) and lanthanides(III): implications for the partitioning of actinides(III) and lanthanides(III)

New hydrophobic, tetradentate nitrogen heterocyclic reagents, 6.6'-bis-(5,6-dialkyl- 1,2,4-triazin-3-yl)2,2'-bipyridines (BTBPs) have been synthesised. These reagents form complexes with lanthanides and crystal structures with 11 different lanthanides have been determined. The majority of the structures show the lanthanide to be 10-coordinate with stoichiometry [Ln(BTBP)(NO3)(3)] although Yb and Lu are 9-coordinate in complexes with stoichiometry [Ln(BTBP)(NO3)(2)(H2O)](NO3). In these complexes the BTBP ligands are tetradentate and planar with donor nitrogens mutually cis i.e. in the cis, cis, cis conformation. Crystal structures of two free molecules, namely C2-BTBP and CyMe4-BTBP have also been determined and show different conformations described as cis, trans, cis and trans, trans, trans respectively. A NMR titration between lanthanum nitrate and C5-BTBP showed that two different complexes are to be found in solution, namely [La(C5-BTBP)(2)](3+) and [La(C5-BTBP)(NO3)(3)]. The BTBPs dissolved in octanol were able to extract Am(III) and Eu(III) from 1 M nitric acid with large separation factors.

Novel lanthanide luminescent materials based on complexes of 3-hydroxypicolinic acid and silica nanoparticles

New lanthanide complexes of 3-hydroxypicolinic acid (HpicOH) were prepared: [Ln(H2O)(picOH)(2)(mu-HpicO)].3H(2)O (Ln = Eu, Tb, Er). The complexes were characterized using photoluminescence, infrared, Raman, and H-1 NMR spectroscopy, and elemental analysis. The crystal structure of [Eu(H2O)(picOH)(2)(mu-HpicO)] . 3H(2)O 1 was determined by X-ray diffraction. Compound 1 crystallizes in a monoclinic system with space group P2(1)/c and cell parameters a = 9.105(13) Angstrom, b = 18.796(25) Angstrom, and c = 13.531(17) Angstrom, and beta = 104.86(1) deg. The 3-hydroxypicolinate ligands coordinate through both N,O- or O,O- chelation to the lanthanide ions, as shown by X-ray and spectroscopic results. Photoluminescence measurements were performed for the Eu(III) and Tb(III) complexes; the Eu(III) complex was investigated in more detail. The Eu(III) compound is highly luminescent and acts as a photoactive center in nanocomposite materials whose host matrixes are silica nanoparticles.

Synthesis and structural characterization of Eu(III)-doped Zn7Sb2O12

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Luminescence of Eu(III) beta-diketone complex supported on functionalized macroporous silica matrix

This work reports on the photoluminescent properties of the complex diequatris(thenoyltrifluoroacetonate) europium(III), which was adsorbed or supported on tubes of modified surface silica matrix. The luminescence data and the experimental intensity parameter results evidence the existence of high interactions between the complex [Eu(tta)(3)(H2O)(2)] and the modified surface matrix. The anchored complex on macroporous silica shows higher intensity parameter values suggesting that the Eu-0 bond becomes more covalent than the adsorbed one. Therefore, the hypersensitive character of the D-5(0) --> F-7(2) transition increases evidencing a high contribution of the dynamic coupling mechanism possibly due to highly polarizable chemical environments occupied by europium(III) ion. The lifetimes of the complex on silica matrices were measured. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Synthesis and thermal characterization of luminescent powers of terbium(III) with mixed ligands

This work deals with the synthesis and thermal decomposition of complexes of general formula: Ln(beta-dik)(3)L (where Ln=Tb(+3), beta-dik=4,4,4-trifluoro-1-phenyl-1,3butanedione(btfa) and L=1,10-fenantroline(phen) or 2,2-bipiridine(bipy). The powders were characterized by melting point, FTIR spectroscopy, LTV-visible, elemental analysis, scanning differential calorimeter(DSC) and thermogravimetry(TG). The TG/DSC curves were obtained simultaneously in a system DSC-TGA, under nitrogen atmosphere. The experimental conditions were: 0.83 ml.s(-1) carrier gas flow, 2.0 +/- 0.5 mg samples and 10 degrees C.min(-1) heating rate. The CHN elemental analysis of the Tb(btfa)(3)bipy and Tb(btfa)(3)phen complexes, are in good agreement with the expected values. The IR spectra evinced that the metal ion is coordinated to the ligands via C=O and C-N groups. The TG/DTG/DSC curves of the complexes show that they decompose before melting. The profiles of the thermal decomposition of the Tb(btfa)3phen and Tb(btfa)3bipy showed six and five decomposition stages, respectively. Our data suggests that the thermal stability of the complexes under investigation followed the order: Tb(btfa)(3)phen < Tb(btfa)(3)bipy.

Thermal studies of solid 4-chlorobenzylidenepyruvates of heavy lanthanides(III) and yttrium(III)

Solid-state compounds of general formula LnL(3).2H(2)O, where Ln is heavier trivalent lanthanides and yttrium, L is 4-chlorobenzylidenepyruvate have been synthetised.On heating these compounds decompose in steps. They lose the hydration water in the first step and the thermal decomposition of the anhydrous compounds occurs with the formation of oxochloride (Eu, Gd); mixture of oxide and oxochloride that decrease with increasing of atomic number of metal (Tb-Tm); or oxide (Yb, Lu, Y) as final residue, up to 900degreesC. The dehydration enthalpies found for terbium, holmium, ytterbium and yttrium compounds were: 34.93, 42.40, 57.39 and 62.24 kJ mol(-1), respectively.

Terbium(III) and dysprosium(III) 8-connected 3D networks containing 2,5-thiophenedicarboxylate anion: Crystal structures and photoluminescence studies

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis, characterization and thermal behaviour of heavy lanthanide and yttrium pyruvates in the solid state

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)