Photochemical properties of mixed-ligand complexes europium carboxylates

The photochemical behavior of mixed-ligand complexes of europium carboxylates with nitrogen-and phosphorus-containing neutral ligands of island and dimer types, Eu(L)₃ · xD · nH₂O and [Eu(L)₃ · xD]₂ · nH₂O (L is the trifluoroacetate, toluate, or cinnamate anion), was studied. During UV irradiation of the complexes of europium carboxylates with 1,10-phenanthroline and 2,2′-dipyridyl, a luminescence buildup was observed. EPR measurements demonstrated that the observed buildup of luminescence from europium occurs in parallel with the increase of the concentration of radical anions formed from neutral ligands.     

Luminescence and magnetic properties of mixed-ligand europium trifluoroacetates

The luminescence and magnetic properties of mixed-ligand europium trifluoroacetates with nitrogen- and phosphorus-containing neutral ligands [Eu(TFA)₃ · 3H₂O]₂ and Eu(TFA)₃ · 2D · nH₂O were studied (here TFA is the trifluoroacetic acid anion, and D is Phen (1,10-phenanthroline), n = 1; DMF (dimethylformamide), n = 1; or TPPO (triphenylphosphine oxide), n = 3). The molar magnetic susceptibility increased in the series of complex compounds Eu(TFA)₃ · 2Phen · H₂O < [Eu(TFA)₃ · 3H₂O]₂ < Eu(TFA)₃ · 2DMF · H₂O < Eu(TFA)₃ · 2TPPO · 3H₂O. Correlations were found between the luminescent and magnetic characteristics of the complex compounds.     

Tuning the properties at heterobimetallic core: mixed-ligand bismuth-rhodium paddlewheel carboxylates

Mixed-ligand heterometallic compounds [BiRh(O2CCF3)4-x(O2CR)x] (R = But, x = 2 (cis); R = Me, Bui, x = 1) have been obtained by gas-phase reactions of bismuth(II) trifluoroacetate with the corresponding rhodium(II) carboxylate. This synthetic approach was found to be very effective for tuning the properties and introduction of chiral ligands at a heterobimetallic core.     

Mechanochemical synthesis of mixed-ligand europium β-diketonates with nitrogen-containing neutral ligands

The solid-phase reaction between europium salts of β-diketones and nitrogen-containing neutral ligands in a planetary mill produces luminescent mixed-ligand compounds Eu(β-dic)₃ · D, where β-dic stands for dibenzoylmethane (DBM), benzoylacetone (BA), thenoyltrifluoroacetone (TTA), or benzoyltrifluoroacetone (BTFA); and D stands for 1,10-phenanethroline (Phen), 2,2-dipyridyl (Dipy), or diphenylguanidine (DPG). The mechanosynthesis and yield of lanthanide β-diketonates are studied as affected by the treatment parameters and the nature of the reagents. Powder X-ray diffraction demonstrates a staged course of the mechanochemical synthesis. Examination of formation-rate curves shows that grinding/stirring is the rate-controlling stage of the process. Thermogravimetric analysis (TGA) shows that the mechanosynthesis can proceed in the self-propagation mode. The relative luminescence intensity is determined as a function of treatment time. Particles of the mechanically activated mixture have sizes of 10–100 μm.     

Mössbauer study of mixed-ligand complexes of europium(III)

A series of europium(III) mixed complexes was prepared containing 1,10-phenanthroline or 2,2-bipyridine as neutral ligand and simple inorganic anions or benzoate and its derivatives as ionic ligands. The Mössbauer spectra of the products indicated that both types of ligands were directly coordinated to the central europium(III) atom. The Mössbauer isomer shift values reflected both electron shifting and steric effects of the substituents on the ligand. The quadrupole splitting values pointed to the similar symmetry of the electron shell of the europium in almost all complexes with analogous composition. The IR spectra provided evidence of the binding mode of the carboxylate groups in the complexes containing benzoate or its derivatives. The x-ray photoelectron spectra of the compounds demonstrated the effects of electrophilic and nucleophilic substituents on the electron binding energies in the europium, oxygen, and nitrogen orbitals.     

Fluorescence enhancement by gadolinium of the europium or samarium-dibenzoylmethane-diethylamine system

A fluorescence enhancement produced by adding Gd³⁺, Y³⁺, Tb³⁺, La³⁺ or Lu³⁺ to europium or samarium-dibenzoylmethane-diethylamine was observed. Gd³⁺ enhanced the fluorescence intensity by 2–3 orders of magnitude compared with the system without Gd³⁺. The new system was used for the simultaneous determination of traces of Sm³⁺ and Eu³⁺ in the ranges 1.0 × 10^?9?8.0 × 10^?8 M and 1.0 × 10^?11?4.0 × 10^?9 M, respectively, and the detection limits were 5 × 10^?13 M for Sm³⁺ and 8 × 10^?14 M for Eu³⁺. The luminescence mechanism of the system is discussed.     

Fluorescence of europium(III) in a flouride glass containing zirconium

Europium(III) incorporated in a new zirconium barium flouride glass shows 14 luminescent transitions (at 300 K) from ⁵D_J (J= 0,1,2,3) to ⁷F_J (_J = 0,1,2,3,4) which are compared with Judd-Ofelt parameters for induced electric dipolar radiation, as well as for calculated magnetic dipolar transition probabilities.     

DNA binding and photocleavage properties of two mixed-ligand oxovanadium complexes

An oxovanadium complex [VO(satsc)(bipy)] (1) (satsc = salicylaldehyde thiosemicarbazone, bipy = 2,2′-bipyridine) and its dibromo derivative [VO(3,5-dibrsatsc)(bipy)] (2) (3,5-dibrsatsc = 3,5-dibromosalicylaldehyde thiosemicarbazone) have been synthesized and characterized by elemental analysis, IR, ES-MS and ¹H NMR. The interaction of these two complexes with calf-thymus DNA (CT-DNA) was studied using UV/Vis, fluorescence spectroscopic titration, viscosity measurements and thermal denaturation. The results suggest that complexes 1 and 2 interact with CT-DNA by intercalative modes. The DNA-binding affinity of complex 1 is larger than that of complex 2. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated by gel electrophoresis experiments. Both complexes exhibit significant DNA cleavage activity, and complex 1 showed greater cleaving efficiency than complex 2.     

Synthesis and spectral properties of europium phthalocyanine complexes

Methods for the synthesis of europium complexes with phthalocyanine and thenoyltrifluoroacetonate (tta) or ferrocenoyltrifluoroacetonate (fta) ligands are discussed. The spectral characteristics of the complexes PcEu(tta)(ttaH) and PcEu(fta)(ftaH) (Pc is phthalocyanine) are studied.     

The preparation and fluorescence properties of europium nanoparticles

A new structured metallic nanomaterial of europium nanoparticle was prepared using tannic acid as the reductive agent,and nanoeuropium protein conjugates were synthesized by the method of lipoic acid modification on the surface of nanoparticle,which opens a new field of application of lanthanides in nanotechniques.Their properties were also characterized by UV-vis absorption spectroscopy,transmission electron microscopy (TEM),and fluorescence spectroscopy.The europium nanoparticle and its protein conjugates solution were stable and water-soluble.The fluorescence intensity of the composite europium nanoparticles was significantly increased in the presence of trace protein,and was linear proportional to the concentration of proteins under optimum conditions.According to this,a fluorimetric method for the determination of protein was developed in this paper.     

Fluorescence characteristics of europium ions stabilized in solid polymer electrolytes containing polyether structure

Polyethylene oxide (PEO) oligomers can dissolve lanthanide salts. The terminal hydroxyl groups of PEO affect the solubility of the lanthanide salts in the PEO considerably. However, no intensive fluorescence was observed from Eu³⁺ dispersed in PEO or other ion-conductive polymers containing terminal hydroxyl groups, because of the quenching effect of the terminal hydroxyl groups. Copolymer of ω-methoxy oligo(oxyethylene) methacrylate and methyl methacrylate (P(MEOM-co-MMA)) could dissolve small amount of Eu(NO₃)₃, but the copolymer film containing Eu³⁺ shows intensive fluorescence (Ex = 269.0 nm, Em = 570.0 nm). This was prepared as a soft film, and there was a clear dependence of the Eu³⁺ concentration on the fluorescence intensity. A linear relation between the film thickness and the fluorescence intensity was also observed. Little fluorescence was found for Eu³⁺ in the blend of the corresponding two homopolymers, i.e. poly-(ω-methoxy oligo (oxyethylene) methacrylate) (PMEOM) and poly(α-methyl methacrylate) (PMMA). This strongly suggests that intensive fluorescence requires a mixed state of MEOM and MMA units at molecular level.     

Synthesis, structure and optical properties of rare-earth benzene carboxylates

Two series of rare-earth isophthalates of the general formula, [M(2)(H(2)O)][{C(6)H(4)(COO)(2)}(2){C(6)H(4)(COOH)(COO)}(2)].H(2)O, M=La (I), Pr (Ia), and Nd (Ib) and [M(2)(H(2)O)(2)][{C(6)H(4)(COO)(2)}(3)].H(2)O, M=Y (II), Gd (IIa), and Dy (IIb) have been prepared by the reaction of the corresponding trivalent lanthanide salts and isophthalic acid under mild hydrothermal conditions. The La (I), Pr (Ia) and Nd (Ib) have MO(9) polyhedra connected to the isophthalate anions forming a two-dimensional structure, whereas Y (II), Gd (IIa) and Dy (IIb) have MO(7) and MO(8) polyhedral units connected to the isophthalate anions forming a different, but related two-dimensional structure. Both the structures are stabilized by hydrogen bonding and pi...pi/CH...pi interactions. Partial substitution of Eu and Tb (2 and 4%) at the La (I) and Y (II) sites give rise to characteristic red/pink or green luminescence, indicating a ligand-sensitized metal-centered emission. The Nd (Ib) compound shows interesting UV and blue emission through an up-conversion process.     

Fluorescence properties of pyrylretinol

A fluorescent analog of retinol, 3,7-dimethyl-9-(1-pyryl)-2E,4E,6E,8E-nonatetr aene-1-ol (referred to as pyrylretinol, or 1) has been synthesized. The fluorescence properties (e.g. quantum yield, lifetime, steady-state anisotropy, and excitation/emission spectra) of this compound in various organic solvents and in dimyristoylphosphatidylcholine (DMPC) liposomes have been studied, and the results are compared with those obtained from 3-methyl-5-(1-pyryl)-2E,4E-pentadiene-1-ol (2), which has the same fused aromatic ring system but a much shorter acyclic chain. 1 and 2 form excimer in aqueous media and fluorescence anisotropies of both 1 and 2 in DMPC liposomes exhibit an abrupt decrease at approximately 21-23 degrees C, which coincides with the main phase transition temperature of DMPC liposomes, indicating that both compounds may be a useful membrane probe. In addition, the binding and quenching capability of pyrylretinol (1) to bovine serum albumin has been investigated. Pyrylretinol (1) binds with BSA with a binding constant of 3.6 x 10(4) M-1, although the value is somewhat lower than that obtained for retinol (3.06 x 10(5) M-1). Pyrylretinol (1) also quenches the BSA intrinsic fluorescence with the quenching rate constant of 1.67 x 10(13) M-1 s-1 and the value is lower than that obtained for retinol (4.06 x 10(13) M-1 s-1). The binding and quenching studies suggest that pyrylretinol (1) may serve as a useful fluorescence probe for structure/function studies of different retinoid binding proteins.     

Fluorescence of the 5Do state of the europium ion in the gas phase

The fluorescence of vapors of europium dipivaloylmethanate (EuL₃), excited by pulsed UV radiation, has been investigated. The fluorescence was observed in the transition ⁵D_o ⁷F₂ of the europium ion (Eu³⁺) (wavelength 6120 Å). An increase of the fluorescence signal by a factor of 3 was established when the cell with the EuL₃ vapors was placed in the optical resonator.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 367–370, May–June, 1985.     

Peculiarities of the excitation energy transfer in europium and terbium aromatic carboxylates and nitrate complexes with sulfoxides: Blocking effect

The influence of modification of the aromatic ligands on the excitation energy transfer to Ln³⁺ ions in europium and terbium carboxylates and nitrates was examined. The luminescence excitation spectra of three groups of the europium and terbium compounds: phenyl-, diphenyl-, triphenylacetates, phenoxyacetates and triphenylpropionates; 1- and 2-naphthylcarboxylates and 2-naphthoxyacetates; lanthanide nitrates with diarylsulfoxides (diphenyl- and dibenzylsulfoxides) and dialkylsulfoxides were investigated. The spectra of adducts of terbium phenylcarboxylates with 1,10-phenanthroline were also analyzed. The effect of the aliphatic bridges, which decouple the π–π- or p–π-conjugation in the ligand, on the energy transfer to Ln³⁺ ions (so-called blocking effect) was investigated. It was shown, that this decoupling leads to significant lowering of the energy of “ligand–metal ion” charge transfer states (LM CTS) in the europium carboxylate salts, just down to 27,800 cm⁻¹ in europium 2-naphthoxyacetate. As a consequence, the probability of the LM CTS participation in the excitation energy dissipation processes increases. A channel of the excitation energy dissipation in the region of 31,750 cm⁻¹ related to ligand electronic transitions was found in the europium and terbium nitrates with sulfoxides. It was demonstrated that a part of the energy absorbed by the aromatic ligand having aliphatic bridge can be emitted as the ligand fluorescence.     

Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

A modified Robinson-Stokes equation with terms that consider the formation of ionic hydrates and associates is used to describe thermodynamic properties of aqueous solutions of electrolytes. The model is used to describe data on the osmotic coefficients of aqueous solutions of alkali metal carboxylates, and to calculate the mean ionic activity coefficients of salts and excess Gibbs energies. The key contributions from ionic hydration and association to the nonideality of solutions is determined by analyzing the contributions of various factors. Relations that connect the hydration numbers of electrolytes with the parameters of the Pitzer-Mayorga equation and a modified Hückel equation are developed.     

Optical properties and paramagnetic susceptibility of europium gallium garnet

A single crystal of europium gallium garnet has been grown by the flux method and the experimental variation with temperature of its paramagnetic susceptibility has been studied up to 600 K. The crystal field parameters have been calculated for D₂ symmetry. From the derived wavefunctions, the magnetic susceptibility versus temperature was calculated. The experimental and simulated susceptibilities are in good agreement.     

Preparation and biocidal properties of mixed butyl/cyclohexyl trialkyltin carboxylates

Two series of trialkyltin carboxylates containing butyl and cyclohexyl groups on tin, Bu_nCy_3-nSnO₂CR (n = 1, 2; R = n-Pr, Ph, 4-CIC₆H₄, 4-NO₂C₆H₄) have been synthesized and their structures characterized by IR, and ¹¹⁹Sn and ¹³C NMR spectroscopies. The compounds are five-coordinate, carboxylate-bridged polymers when R = n-Pr, while the other aromatic carboxylates are four coordinate. The compounds were also tested for their fungicidal, insecticidal and acaricidal activities.     

Fluorescence properties of nanosized sulfides

The absorption spectra of nanosized sulfides and selenides (ZnS, CdS, CuS, Cu₂S, AgS, In₂S₃, SnS, PbS, Sb₂S₃, FeS, CoS, NiS, CdSe, and Ag₂Se) showed one absorption band with a maximum at wave-lengths shorter than 300 nm. The UV fluorescence spectra of all of these nanosized sulfides in a polyvinyl alcohol film contained maxima at 380–440 nm. Nanosized sulfides are thus characterized by a very large (up to 15000 cm⁻¹) Stokes shift of fluorescence. In a polyvinyl alcohol film, a decrease in the concentration of cadmium sulfide from 0.05 to 0.002 M led to a threefold increase in the fluorescence intensity. The dependence of the degree of fluorescence buildup on the sulfide concentration is nearly linear. An increase in sulfide concentration to more than 5 × 10⁻³ M in solution led to a complete coagulation of particles.     

非标记铕配合物荧光免疫分析法研究: 测定血清中的金属硫蛋白

本文报告一种新型非同位素免疫分析法, 非标记稀土铕配合物荧光免疫分析。它仍以免疫反应为基础, 所不同的是无须制备标记物。较标记免疫分析法简便、快速、在所建立的方法中, 金属硫蛋白(MT)的量与Eu-β-二酮配合物的荧光强度成负相关。测定范围为0-1.3μg/mL, 测定血清中MT的回收率为95%-100%, 相对标准偏差<10%。