Photochemical behavior of luminescent compositions based on antimony(III) and europium(III) complexes in high-pressure polyethylene

Luminescent and photochemical properties of polymer compositions based on the Eu(NO₃)₃(Phen)₂ complex and complexes of antimony(III) halides with diphenylguanidine are investigated. It is found that high-pressure polyethylene (HPPE) containing europium(III) and antimony(III) complexes in combination exhibits efficient transfer of electronic excitation energy from antimony(III) levels to europium(III) levels and photosensitization of europium(III) luminescence. It is shown that the europium(III) and antimony(III) complexes increase the stability of HPPE to UV radiation.     

Luminescent and triboluminescent properties of europium(III) hexafluoroacetylacetonate and trifluoroacetate complexes with triphenylphosphine oxide

Crystalline and strongly luminescent complexes of europium hexafluoroacetylacetonate and trifluoroacetate with triphenylphosphine oxide of Eu(HFAA)₃ · 2TPPO and [Eu(TFA)₃ · 2TPPO(H₂O)]₂ composition are synthesized that demonstrating triboluminescent properties. It is established that the measured photoluminescence and triboluminescence spectra of these noncentrosymmetric complex compounds are identical, due to the characteristic f-f-luminescence of the europium(III) ion.     

Flow injection spectrophotometric determination of europium using chlortetracycline

A flow injection (FI) spectrophotometric determination of europium (III) is described, based on the complexation between europium (III), and chlortetracycline (CTC) in a Tris-buffer pH 8.0 medium. The resulting yellow-coloured complex is measured at its absorption maximum of 400 nm after 100 μl of sample or standard solution containing europium (III) are injected into the merged streams of CTC and Tris-buffer solutions. Optimum conditions for determining μg amounts of europium (III) are achieved by univariate method. Various types of reactors are also investigated. It is shown that the use of a single bead string reactor gives rise to the enhancement of peak height. A linear calibration curve over the range of 0.10-0.60 μg ml⁻¹ europium (III) is established with the regression equation (n=6) Y=34.93X+0.01 and the correlation coefficient of 0.9994 is obtained. A detection limit (3σ) of 0.01 μg ml⁻¹ of europium (III) and the relative standard deviation (R.S.D.) of 4.32% for determining 1.0 μg ml⁻¹ of europium (III) (n=7) are obtained. The recommended method has been applied to the quantitation of europium (III) in spiked water and stream sediment samples with average recoveries of 99.9 and 97.5%, respectively. The sampling rate is found to be 85 h⁻¹.     

Luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids

The luminescent properties of europium(III) and terbium(III) complexes with para- and ortho-ethoxybenzoic acids are studied. The excitation energies of the triplet states of ligands are determined, a hypothesis is made about the efficient luminescence of europium(III) and terbium(III) complexes, the geometry of the coordination polyhedron of a europium complex is established, and the luminescence quantum yields of the complexes in solution are determined.     

Cathodic europium(III) electroluminescence at an oxide-coated aluminum electrode

Electroluminescence is produced at an oxide-coated aluminum electrode during cathodic polarization of the electrode in an acetate solution containing nitrate and traces of europium(III). The europium(III) ion in the ⁵D₀ state is the emitter. Linear log-log calibration plots are obtained for the range 1 × 10^?8?1 × 10^?5 M europium(III). A mechanism for the cathodic luminescence is proposed.     

Solution Chemistry of Europium(III) Aqua Ion at Micromolar Concentrations as Probed by Direct Excitation Luminescence Spectroscopy

Direct excitation europium(III) luminescence spectroscopy is used to study the speciation of aqueous europium(III) ions at micromolar concentrations and near neutral pH. The pH and concentration dependence of the europium(III) ⁷F₀→⁵D₀ excitation peak is consistent with the formation of both mononuclear and dinuclear europium(III) hydroxide complexes at pH 6.5. Luminescence intensity and lifetime quenching studies in the presence of Nd^III at pH 5.0 and 6.5 support the formation of a dinuclear complex at pH 6.5. Steady state excitation and time‐resolved luminescence spectroscopy are consistent with the formation of innersphere nitrate and fluoride complexes, but outersphere perchlorate and chloride complexes at pH 6.5 and 5.0.     

Formation and dissociation kinetics of Eu(III) complexes with H5do3ap and similar dota-like ligands

Complexation kinetics of the europium(III)-H₅do3ap complex (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic acid)) was studied at 25 °C and I = 0.1 M KCl and compared with the analogous H₄dota-like ligands. The mechanism of the formation reactions between the europium(III) ion and H₃do3a, H₄dota and H₄dota analogs having one methylphosphonic (H₅do3ap) or phosphinic acid pendant arms with a propionate side chain (H₅do3ap^PrA) was proposed on the basis of TRLIFS measurements. The experimental data of the dissociation kinetics of the europium(III) complexes with H₅do3ap and H₅do3ap^PrA ligands show that there is no change in reactivity of the complexes due to the side chain of the phosphinic acid bifunctional chelate. The TRLIFS study of the proton-assisted decomplexation reaction of the europium(III) complexes with H₃do3a, H₄dota, H₅do3ap and H₅do3ap^PrA demonstrates different behaviour influenced by a change in the number of water molecules during the reaction. The advantages and disadvantages of the TRLIFS methodology as a new experimental technique for simultaneous evaluation of kinetics and reaction mechanisms are discussed.     

Synthesis of a novel chelating ligand from pentane-2,4-dione and 3-aminopropyl[tris(trimethylsilyloxy)]silane. europium(III) and erbium(III) imino enolates

Acetylacetone reacts with 3-aminopropyl[tris(trimethylsilyloxy)]silane to give a mixture of the isomers 4-[3′-tris(trimethylsilyloxy)silylpropyl]iminopent-2-en-2-ol (90%) and 4-[3′-tris(trimethylsilyloxy)silylpropyl]aminopent-3-en-2-one (10%). According to ¹H and ¹³C NMR data, both isomers exist in the cis-and trans-forms. Anhydrous europium(III) and erbium(III) tris{4-[3′-tris(trimethylsilyloxy)silylpropyl]iminopent-2-en-2-olates} were obtained from the mixture of the isomers and the corresponding propan-2-olates Eu(OPr _i )₃ and Er(OPr _i )₃. The resulting complexes are transparent air-stable liquids that are distillable in vacuo and well soluble in photopolymerizable polyorganosiloxane caoutchoucs and urethane acrylate oligomers. The volatility parameters of the europium(III) complex were studied.     

Vibrational Structure of Methacrylates Europium(Iii) and Lanthanum(Iii): Dft and Ir Spectroscopy Study

DFT-D3/PBE0 and IR spectroscopy are employed to study the vibrational structure of europium(III) and lanthanum(III) methacrylates Ln(Macr)₃ (Ln = Eu, La; Macr is the methacrylate anion, CH₂CH(CH₃)COO^–). The calculated geometric and vibrational characteristics are consistent with the experimental data. By means of the calculation of the Eu₂(Macr)₆·(H₂O)₄ complex the experimental IR spectrum is interpreted. The effect of isomorphic lanthanum substitution for the europium ion in the Eu₂(Macr)₆·(H₂O)₄ complex is studied theoretically. A mechanism is proposed for the effect of the vibrational structure on the optical properties (at the isomorphic replacement of the europium ion and temperature elevation).     

Evaluation of electrochemical charge-transfer rates by using (real) laplace space analysis: Single potential-step chronoamperometry of hexacyanoferrate(III)/(II) and Europium(III)/(II) couples

The one-electron hexacyanoferrate(III)/(II) and europium(III)/(II) redox couples were evaluated by using single-pulse chronoamperometry at a planar glassy carbon electrode (and also a mercury-pool electrode for europium) to test Wijnen's method for calculating heterogeneous electron-transfer rate constants by using (real-axis) Laplace space analysis. The k⁰ values obtained for the former couple in potassium or lithium chloride supporting electrolytes agreed well with published constants obtained by diverse real-time techniques. Transfer coefficients (α⁰) obtained from (? in k^a/?η)_η=0 for LiCl electrolyte were 0.4–0.5, rather than 0.22 previously reported. The cathodic rate values calculated for europium(III) reduciton (in NaClO₄/HClO₄) on both glassy carbon and mercury agreed very well with each other and with published values obtained by d.c. polarography and faradaic impedance measurements. Owing to several factors, including its ability to utilize virtually any set of recorded i(t) data points, Wijnen's Laplace technique offers an attractive alternative to conventional single-pulse analysis in real-time.     

Luminescence of europium(III) β-diketonate complexes in a Nafion membrane

EuL₃ · phen complex compounds (L is benzoylacetone, dibenzoylmethane, or thenoyltrifluoroacetone; phen is 1,10-phenanthroline) were synthesized in a perfluorosulfonic membrane. The results of adsorption measurements suggest that the complexes experience steric hindrances in the membrane pores. The luminescence from intercalates is sensitized due to the increase in the degree of population of the ⁵ D ₀ excited state of europium(III) caused by the transfer of energy from the ligands. Depending on the type of β-diketonate ligand, the adsorption of water on the modified membrane can enhance or suppress the luminescence from the complex.     

Preparation, thermal decomposition and lifetime of Eu(III)-phenanthroline complex doped xerogel

The main purpose of this work is proposing a new method of using non-isothermal formal kinetics analysis to predict the lifetime of luminescent complex materials. The Eu(III)-phenanthroline complex doped xerogel has been in situ synthesized by a catalyst-free sol-gel method. The photoluminescence spectra and TG curves of the xerogel verify the formation and decomposition of Eu(III)-phenanthroline complex in xerogel. The decomposition of the xerogel formally occurs in three steps. The Friedman and FWO isoconversional methods and multivariate non-linear regression method are used for formal kinetic analysis. The overall decomposition process below 800 °C is fitted by three-step consecutive reaction. The best fitted model for each step is F_n (n order reaction, the corresponding function f(α) is (1 − α)ⁿ). Correlation coefficient is 0.99956. The lifetime values of xerogel at different temperatures are predicted based on non-isothermal kinetic models by the 5% decomposition of europium organic complex.     

Synthesis and Properties of Acyclic and Cryptate Europium(III) Complexes Incorporating the 3,3′-Biisoquinoline 2,2′-Dioxide Unit

The lithium and europium(III) cryptates of a macrobicyclic ligand 1 incorporating the 3,3′-biisoquinoline 2,2′-dioxide 2 have been prepared. The Eu(III) complex [Eu(2)₂]Cl₃ has also been obtained. These Eu(III) complexes present characteristic ¹H-NMR spectra containing markedly shifted resonances. They are strongly luminescent; the emission spectra, quantum yields, and lifetimes have been determined.     

Sorption of a complex of europium (III) with acetylacetone on hydrophobized hexadecyl silica gel and hyper crosslinked polysterene

The sorption of a complex of europium (III) with acetylacetone on silica gel chemically modified with hexadecyl groups (SiO₂-C₁₆) and hyper crosslinked polystyrene (HLPS) was studied. Maximum extraction was observed at pH 5–7 when SiO₂-C₁₆ was used as the sorbent and at pH 4–7 in the case of crosslinked polystyrene. The partition coefficients for HLPS and silica gel were calculated as 7 × 10³ and 1 × 10² cm³/g, respectively. Quantitative extraction of the europium (III) complex was possible in dynamic conditions using a microcolumn (length, 10 mm; internal diameter, 3mm) packed with HLPS at pH 5 (10–50 mL sample volume). Desorption of europium using solutions of nitric acid at different concentrations was investigated. Quantitative desorption was achieved using 5 mL of 1 M HNO₃. A linear range of detection was observed at an amount of europium from 5 to 25 μg in a 10-mL sample (650 nm).     

The luminescent properties of polyethylene films with admixtures of luminophores based on europium compounds

Polyethylene films activated with europium(III) complexes with carboxylic acids and Eu(L)₃ · nD · xH₂O + ANT compositions, where L is the trifluoroacetic, toluyl, or cinnamic acid anion and ANT is anthranilic acid, were prepared. The intensity of luminescence of the polymeric compositions depended on the content of luminophores (molar ratio between europium compounds and anthranilic acid). An analysis of the excitation spectra showed that, in polymer—Eu(L)₃ · nPhen · xH₂O + ANT compositions, there was effective energy transfer from phenanthroline to anthranilic acid levels.     

Catalytic activity of some organolanthanoid derivatives in styrene and propene polymerization

Organolanthanoids of several classes were examined as potential styrene and propene polymerization catalysts. They are: molecular hydrides of divalent lanthanoids (samarium, europium, ytterbium); naphthalene and stilbene complexes of neodymium(III), samarium(II), europium(II), ytterbium(II), lutetium(III); amides and alkoxides (including heterobifunctional derivatives) of praseodymium(III), neodymium(III), samarium(II), europium(II), thulium(III), ytterbium(II, III); thiolate of samarium(III); phenyl and phenylethinyl derivatives of europium(II), thulium(III), ytterbium(II); methylytterbium cluster Yb₈ (μ‐CH₃)₁₄(μ‐CH₂)(THF)₆; heterobimetallic samarium(II), ytterbium(II, III) complexes; diazabutadiene ytterbium(III) derivatives; metallic praseodymium and ytterbium, activated by iodine. The highest activity in styrene polymerization revealed hydrides, naphthalene and stilbene complexes of samarium(II), europium(II) and ytterbium(II). In the propene polymerization only [(η⁵‐C₅H₄)CH₂CH­(CH₂OBu)(η¹‐O)]YbMe(THF) displayed noticeable activity.Copyright © 2001 John Wiley & Sons, Ltd.     

Crystal structure of a new binuclear complex bis(2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione-o,o′)-tetraaqua-hexakis(nitrato-o,o′)-dieuropium(III)

A centrosymmetric binuclear complex of europium(III) nitrate with bicyclic bisurea (2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar, Mk) [Eu(C₈H₁₄N₄O₂)(H₂O)₂(NO₃)₃]₂ (I) is synthesized and its atomic structure (CIF file CCDC No. 1451437) is determined. The crystals of I are triclinic: space group \(P\overline 1 \), a = 9.8343(4) Å, b = 10.2544(4) Å, c = 10.9411(4) Å, α = 74.366(3)°, β = 67.734(4)°, γ = 67.673(4)°, V = 934.32(7) ų, ρ(calc.) = 2.03398 g/cm³, Z = 1. The europium atom is coordinated by two oxygen atoms of two Mk molecules connected by a symmetry operation, three bidentate nitrate anions, and two water molecules. The coordination polyhedron of the europium atom is a 10-vertex polyhedron, the Eu…Eu distance is 9.7433(6) Å.     

Thermal behavior of the highly luminescent poly(3-hydroxybutyrate):Eu(tta)3(H2O)2 red-emissive complex

The aim of this study has been to gain a fundamental understanding of the mechanisms governing thermal degradation of luminescent poly(3-hydroxybutyrate) (PHB). PHB was doped with diaquatris(thenoyltrifluoroacetonate) europium(III) complex, [Eu(tta)₃(H₂O)₂], and different luminescent systems were obtained. The thermal-stability of the luminescent films was discussed and the products of decomposition were analyzed. Thermal degradation of PHB:Eu(tta)₃ x % systems (x = 0, 1, 5, 10, and 15 %) was elucidated by means of thermogravimetric analysis (TG), the thermal-stability decreases with the increase of europium complex concentration. The PHB polymer decomposed with evolution of carbon dioxide and 2-butenoic acid molecules. The TG–FTIR results, of the gaseous degradation products of PHB in nitrogen atmosphere, indicated that the polymer is stable at temperatures up to 200 °C. Polymer matrix at concentrations above 5 % decomposed with evolution of water molecules among the other gaseous products, which implied the presence of a hydrated complex in the system. The luminescent films showed more flexibility due to a loss in crystallinity, which suggested a potential usefulness in technical applications.     

Highly sensitive spectrofluorometry of europium(III) as its benzoyltrifluoroacetone complex with trioctylphosphine oxide by means of solvent extraction and vacuum sublimation

Summary A new method for the highly sensitive fluorometric determination of europium(III) as its benzoyltrifluoroacetone (BFA) complex with trioctylphosphine oxide (TOPO) without uncombined BFA in n-hexane has been established by means of solvent extraction and vacuum sublimation. The effect of various factors on the fluorescence intensity of europium(III) was investigated. The fluorescence intensity was measured at 620 nm against rhodamine B as an internal standard under the excitation at 335 nm. It was found that a heating treatment gave rise to the enhancement of the fluorescence intensity for about twice times compared with that without heating treatment. Excellent linearity of the calibration curve of europium(III) was obtained in the range of 0–100 ppb. A few ppb of europium(III) can still be detected with this method. All 13 rare earth metals and cobalt(II) tested gave a somewhat positive error. Aluminium(III), iron(III), and copper(II) caused a negative error. The interference of aluminium(III) and iron(III) was removed by extraction with 0.1 mol/l 8-quinolinol in chloroform at pH 4.0, while the problem of cobalt(II) and copper(II) was solved by masking with 0.1 mol/l Na₂S₂O₃ in aqueous solution.

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Hochempfindliche spektrofluorimetrische Bestimmung von Europium(III) als Benzoyltrifluoracetonkomplex mit Trioctylphosphinoxid mit Hilfe der Lösungsextraktion und Vakuumsublimation