Hot electron-induced electrogenerated chemiluminescence of rare earth(III) chelates at oxide-covered aluminum electrodes

Aromatic Gd(III) and Y(III) chelates produce ligand-centered emissions during cathodic pulse polarization of oxide-covered aluminum electrodes, while the corresponding Tb(III) chelates produce metal-centered⁵D₄ →⁷F_j emissions. It was observed that a redox-inert paramagnetic heavy lanthanoid ion, Gd(III), seems to enhance strongly intersystem crossing in the excited ligand and direct the deexcitation toward a triplet-state emission, while a lighter diamagnetic Y(III) ion directs the photophysical processes toward a singlet-state emission of the ligand. The luminescence lifetime of Y(III) chelates was too short to be measured with our apparatus, but the luminescence lifetime of Gd(III) chelates was between 20 and 70 μs. The mechanisms of the ECL processes are discussed in detail. Preliminary results of electrogenerated triplet-state emission of one of the ligands used in this work have been published in a letter elsewhere [9].     

Raman,FT‐IR,and DFT studies of 3,5‐pyrazoledicarboxylic acid and its Ce(III) and Nd(III) complexes

3,5‐Pyrazoledicarboxylic acid was used as a ligand for the synthesis of its Ce(III) and Nd(III) complexes. The complexes of Ce(III) and Nd(III) with 3,5‐pyrazoledicarboxylic acid were synthesized and their compositions were determined by elemental analysis. Vibrational study in the solid state of 3,5‐pyrazoledicarboxylic acid and its new Ce(III) and Nd(III) complexes was performed by IR and Raman spectroscopy. The changes observed between the IR and Raman spectra of the ligand and of the complexes allowed us to establish the coordination mode of the metal in both complexes. The comparative vibrational analysis of the free ligand and its lanthanide(III) complexes gave evidence that 3,5‐pyrazoledicarboxylic acid binds Ln(III) through the deprotonated carboxylic oxygens. The density functional theory (DFT) calculated geometries, harmonic vibrational modes and Raman scattering activities of the ligand were in good agreement with the experimental data, and a complete vibrational assignment is being proposed. The experimental IR and Raman bands of the ligand were assigned to normal modes on the basis of DFT calculations. The effect of the intramolecular hydrogen bonds in the ligand on vibrational mode positions is also discussed. The characteristic IR and Raman bands of 3,5‐pyrazoledicarboxylic acid and its lanthanide complexes were specified and discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Pulsed dipolar spectroscopy distance measurements in biomacromolecules labeled with Gd(III) markers

This work demonstrates the feasibility of using Gd(III) tags for long-range Double Electron Electron Resonance (DEER) distance measurements in biomacromolecules. Double-stranded 14- base pair Gd(III)-DNA conjugates were synthesized and investigated at K(a) band. For the longest Gd(III) tag the average distance and average deviation between Gd(III) ions determined from the DEER time domains was about 59±12?. This result demonstrates that DEER measurements with Gd(III) tags can be routinely carried out for distances of at least 60?, and analysis indicates that distance measurements up to 100? are possible. Compared with commonly used nitroxide labels, Gd(III)-based labels will be most beneficial for the detection of distance variations in large biomacromolecules, with an emphasis on large scale changes in shape or distance. Tracking the folding/unfolding and domain interactions of proteins and the conformational changes in DNA are examples of such applications.     

Incorporation of Siderophore Binding Sites in a Dipodal Fluorescent Sensor for Fe(III)

A new fluorescent probe 3, has been developed for the detection of Fe(III) in water based samples. The design of 3 involved the incorporation of Fe(III) binding sites observed in naturally occurring Siderophores into a synthetic sensing assembly. The probe, containing two Schiff base receptors connected to a mesitylene platform, was prepared in two steps. The dipodal sensor displayed good selectivity for Fe(III) when tested against other physiological and environmentally important metal ions, in HEPES buffered solution at pH 7.0, through a quenching of the fluorescent intensity. Stern-Volmer analysis of this quenching interaction indicated a 1:1 (host : guest) binding stoichiometry between the probe and Fe(III). The association constant, K _a calculated using the Benesi-Hildebrand equation was found to be 3.8 × 10⁴ M⁻¹. Crucially, the sensor was capable of measuring Fe(III) competitively in solutions containing both Fe(III) and Cu(II). Thus, the adoption of Fe(III) binding sites found in nature, into synthetic luminescent assemblies has proven an effective design strategy for the development of new Fe(III) probes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A Study on Some Europium(III) Supramolecules by Electrospray Mass Spectrometry

Electrospray mass spectrometry (ESMS) of a series of europium(III) supramolecules derived from tris(2-aminoethyl)amine (tren) and 2,6-diformyl-4-R-phenol (R = F, Cl, t-Butyl) is described. the peaks were assigned by both m / Z values and the isotope distributions. the ESMS are largely affected by the nature of the cryptates.     

Theoretical oscillator strengths for some transitions in P(III), As(III), Sb(III) and Bi(III)

Relativistic as well as non-relativistic oscillator strengths have been calculated for transitions in the principal sharp and diffuse series of P(III), As(III), Sb(III) and Bi(III) spectra. The radial integrals were computed by employing the wave functions obtained from a semiempirical method which included exchange effects. A comparison is presented for our calculated f_ik values with experimental and other theoretical data. The influence of relativistic effects on oscillator strengths for transitions in the P(III) through Bi(III) homologous sequence is discussed.     

Kinetics and mechanism of uncatalysed and ruthenium(III) catalysed oxidation of allyl alcohol by diperiodatoargentate(III) in aqueous alkaline medium

The oxidation of allyl alcohol by diperiodatoargentate(III) (DPA) is carried out both in the absence and presence of ruthenium(III) catalyst in alkaline medium at 298 K and a constant ionic strength of 1.1 mol dm^?3 was studied spectrophotometrically. The oxidation products in both the cases were acrolein and Ag(I), identified by spectral studies. The stoichiometry is same in both the cases, that is, [AA]/[DPA] = 1:1. The reaction shows first order in [DPA] and has less than unit order dependence each in both [AA] and [Alkali] and retarding effect of [IO] in both the catalysed and uncatalysed cases. The order in [Ru(III)] is unity. The active species of DPA is understood to be as monoperiodatoargentate(III) (MPA) in both the cases. The uncatalysed reaction in alkaline medium has been shown to proceed via a MPA–allyl alcohol complex, which decomposes in a rate determining step to give the products. In catalysed reaction, it has been shown to proceed via a Ru(III)‐allyl alcohol complex, which further reacts with one molecule of MPA in a rate determining step to give the products. The reaction constants involved in the different steps of the mechanisms were calculated for both reactions. The catalytic constant (K_c) was also calculated for catalysed reaction at different temperatures. The activation parameters with respect to slow step of the mechanisms were computed and discussed for both the cases. The thermodynamic quantities were also determined for both reactions. Copyright © 2007 John Wiley & Sons, Ltd.     

Nonlinear refractive index measurement of tris(acetylacetonato) manganese(III) solution

We present the results from investigations of the nonlinear refractive index and nonlinear absorption coefficient of tris(acetylacetonato)manganese(III) solution, using Z-scan technique with a low-power continuous-wave laser at 514 nm. We demonstrate that the light-induced nonlinear refractive index variation leads to strong self-focusing and self-defocusing. A pump and probe technique was used to investigate the cause of nonlinearity. Furthermore, the nonlinear absorption effect was utilized to demonstrate all optical switching.     

Simultaneous Spectrophotometric Determination of Iron(II) and Iron(III) in Mixtures Using Di-2-pyridyl Ketone Benzoylhydrazone

A method for simultaneous spectrophotometric determination of total iron, iron(II) and iron(III) in mixtures containing other metal ions has been described. The method is based on the complexation of iron with di-2-pyridyl ketone benzoylhydrazone (DPKBH) in 50% (v/v) ethanolic solution. Iron(II) complex with DPKBH exhibits two absorption maxima at 360 and 650 nm. meanwhile iron(II1) complex with DPKBH exhibits only one maximum at 360nm. Iron(II) and iron(III) complexes with DPKBH have similar behaviour at 360nm. Iron forms 1:2 complexes with the reagent. Beer's laws are obeyed over the ranges 0.1–2 μgml-1 and 0.4–5 μgrn1-l for iron(II) complexes at 360 and 650nm respectively. Iron(III) showed results similar to those obtained for iron(II) at 360nm. The effect of pH, effect of excess reagent. the stability of complexes. and the tolerance limit of many metal ions have been reported. The method is applied to the determination of total iron, iron(I1). and iron(II1) in synthetic solutions.     

The nature of the effect of Gd(III) on fluorescence of Ln(III) chelates in water solutions

The intensity of fluorescence of Eu(III) and Sm(III) ions sensitized by molecules of n-benzoyltrifluoroacetone and 1,10-phenanthroline introduced in a water solution in a ratio of 3: 1 is studied as a function of the ion concentration in the solution. The comparison of the fluorescence decay curves of Eu(III) and Sm(III) in D₂O and H₂O (pH≥7) solutions containing 10^?4 M of n-Cl-BTFA and 3×10^?5 M of 1,10-phen and the values of τ_fl of Sm(III) in themselves (51–90 μs) are indicative of an insignificant content of water molecules in the first coordination sphere of ions. The effect of other ions on I _fl and τ_fl of Eu(III) ions is studied under these conditions. The intensity of fluorescence of Eu(III) in solutions of 10^?4 M Cl-BTFA and 3×10^?5 H 1,10-phen is found to increase by 1–2 orders of magnitude in the presence of Y(III) and Gd(III) ions, and the magnitude of this effect is unaffected by deoxygenation of the solution. The introduction of a third ion Nd(III) in the solution is shown to attenuate the influence of Gd(III) on I _fl of Eu(III) for Nd(III) concentrations commensurable with the Eu(III) concentration in the solution. The strength of the influence of Gd(III) ions on I _fl of Eu(III) is found to depend on the method of preparation of the solution. The analysis of the results obtained testifies that inhomogeneities consisting of chelates of lanthanide ions displaced from the water structure appear in water. The presence of these inhomogeneities results in efficient energy transfer from ligands of Gd(III) chelates to Eu(III) chelates, which is the reason for the increasing I _fl of Eu(III). The possibility of using data on the enhancement of I _fl of Eu(III) in the presence of Gd(III) and on the reduction of τ_fl of Eu(III) in the presence of Nd(III) for estimating dimensions and structures of displaced systems is discussed.     

Enhanced fluorescence of Tb(III), Dy(III) perchlorate by salicylic acid in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth perchlorate complexes had been synthesized by using bis(benzoylmethyl) sulfoxide as first ligand (L=C₆H₅COCH₂SOCH₂COC₆H₅), salicylic acid as second ligand (L^′=C₆H₄OHCOO⁻). The compounds were characterized by elemental analysis, TG-DSC and molar conductivities in DMF solution. The composition was suggested as [REL₅L′](ClO₄)₂·nH₂O (RE=Tb, Dy; n=6, 8 ). Based on IR, ¹HNMR and UV spectra, it showed that the first ligand, bis(benzoylmethyl) sulfoxide (L), bonded with Tb(III), Dy(III) ions by the oxygen atom of sulfinyl group. The second ligand, salicylic acid group (L′), not only bonded with RE(III) ions by one oxygen atom of carboxyl group but also bonded with RE(III) ions by oxygen atom of phenolic hydroxyl group. In bis(benzoylmethyl) sulfoxide system, fluorescent spectra of the complexes showed that the luminescence of Tb(III), Dy(III) ions was enhanced by the second ligand salicylic acid. The ternary complexes had stronger fluorescence than the binary ones where only bis(benzoylmethyl) sulfoxide acted as ligand. Phosphorescent spectra of the two ligands indicated that the coordination of salicylic acid resulted in the matching extent increasing between the triplet state of ligand and excited state of the rare earths. The relationship between fluorescence lifetime and fluorescence intensity was also discussed.     

Calculated Stark widths of isolated S(III) and S(IV) lines

Calculations have been performed on the electron-impact broadening of isolated lines from doubly-ionized and triply-ionized sulphur emitted from a plasma of electron density 10¹⁷ cm^-3 and temperature 28,500°K. These have been compared with results of measurements performed by Plati?a, Popovi?, Dimitrijevi?, and Konjevi? on a low-pressure, pulsed arc. Good overall agreement has been obtained for both ionization stages, in confirmation of our earlier conclusions based on a similar comparison for oxygen ion lines. The present calculations have been compared with calculations based upon two simplified models of Griem and the classical-path approximation of Sahal-Bréchot. Our calculated widths are in better agreement with experiment than with values obtained from the first two models; for the two multiplets, where comparison is possible, good agreement is found with the widths obtained by Sahal-Bréchot. We conclude that the present model, whereby the effective Gaunt factor is calculated, is capable of predicting reliable values for the Stark widths of isolated ion lines. Comparison with experiment [for S(III) indicates that, provided a sufficiently complete set of perturbing levels is used in the calculations, the present formula for ? may also be used for below-threshold energies in the determination of the elastic contribution to the broadening. For S(IV), an ambiguity remains in this regard, owing chiefly to a scarcity of available experimental data.     

Structure and electrochemical performance of Y(III) and Al(III) codoped amorphous nickel hydroxide

Amorphous nickel hydroxide codoped with rare earths Y(III) and Al(III) has been synthesized by the chemical precipitation method combined with the rapid freezing technique. The microstructure and morphology of the prepared sample were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectra. The electrochemical performance of the sample was characterized by the charge/discharge test and cyclic voltammetry. The results show that this amorphous nickel hydroxide codoped with Y(III) and Al(III) has many structural defects and therefore results in a relatively high specific capacity (351.83 mA h g^?1 at a charge/discharge rate of 0.2 C) and good electrochemical reversibility.     

Effect of Bonding Scandium(III) ion to 1,3-Diketones on Their Luminescent Properties

We study the influence of bonding Sc(III) ion with 1,3-diketonate ligands on luminescent properties of 1,3-diketones in two complexes by means of optical spectroscopy. We show that the sensitization of the ligand luminescence of the complexes obtained increases from 0.8% for neat ligands and to 4% for the synthesized compounds; this fact is confirmed by the quantum yield measurements.     

Eu(III) complexation of phenyltrisalanine and phenylbisalanine in aqueous solution studied by photoluminescence and UV spectroscopy

The Eu(III)-coordination of phenyltrisalanine (Pta) 1, in aqueous solution was investigated. The photoluminescence data suggested that the chelating effect of Pta places the metal ion on the face of the aromatic ring as proposed in 4. Furthermore, Eu(III) is usually used as a substitute for Ca(II) in spectroscopic studies and the formation of a 1:1 complex between Pta and Eu(III) indicated the possibility that Pta may be used as a Ca(II) binder. For comparison, phenylbisalanine (Pba) 2, was subjected to similar studies and was found to behave more like phenylalanine.     

Simultaneous observation of low temperature 4f-4f and 3d-3d emission spectra in a series of Cr(III)(ox)Ln(III) assembly

We report here the low temperature emission spectra in the heterometal dinuclear 3d-4f assembled molecular system [(acac)₂Cr^III(μ-ox)Ln^III(HBpz₃)₂] (Cr(ox)Ln:acac⁻=acetylacetonate, ox²⁻=oxalate, HBpz₃⁻=hydrotris(pyrazol-1-yl)borate; Ln=La, Nd, Ho, Er , Tm and Yb) in comparison with those of Na[Cr(acac)₂(ox)] and [(HBpz₃)₂Ln(μ-ox)Ln(HBpz₃)₂](Ln=Nd and Er). From 10 to 150 K the Cr(ox)Ln complexes show a broad emission band around 800 nm from the ²E state of Cr(III) moiety. At room temperature no ²E-⁴A₂ emission was observed in the Cr(ox)Ln except for the La and Lu complexes. On warming from 10 to 300 K rapid quenching of the ²E-⁴A₂ emission of Cr(III) is suggested to result from the energy transfer from Cr to Ln in the Cr(ox)Ln. The excitation spectra and the life-time were also measured with monitoring the 4f-4f emission peaks of the Cr(ox)Yb complex.     

Thermal transitions and degradative processes in Fe(III)-tetracarboxyphthalocyanine-grafted poly(N-vinylcarbazole)

The introduction of 2,9,16,23-tetracarboxy-Fe(III)phthalocyanine [Fe(III)tcPc] units onto fractions of poly(N-vinylcarbazole) (PVK) by Friedel-Crafts reaction leads to amorphous PVK-based grafted compounds that show major interchain distances by the wide-angle x-ray scattering (WAXS) technique. Glass transition temperatures of the products are lower than the main glass transition temperature of PVK and are attributed to local movements of the voluminous added groups. Dynamic thermogravimetric experiments show decarboxylation processes within the 250°C-500°C range and little weight loss. The large remaining residue, up to 70% of the sample at 800°C, is suggested to be the consequence of successive cross-linking reactions. The Fourier transform infrared (FTIR) spectrum of the residue is similar to that of the grafted sample before degradation.     

Calculating Hamiltonian parameters for Yb~(3+) in a low-symmetry lattice site,and fitting the structure and levels of Yb~(3+) :TaO_4 (= Gd,Y,and Sc)

An iterative method is used to find the values of the Hamiltonian parameters for Yb3+ in a given low-symmetry crystalline site.Samples of Yb3+:RETaO4(RE = Gd,Y,and Sc) were prepared and their structures were determined.Based on the obtained structural data,their orbital-spin parameters and crystal field parameters were fitted by the superposition model(SM).Using the crystal field parameters obtained by the SM fitting as the initial parameters,the Hamiltonian parameters were fitted iteratively.The calculated and experimental energy levels for Yb3+:RETaO4 are consistent,and the maximal mean-root-square deviation is only 2.84 cm-1,indicating that the method is effective to determine the Hamiltonian parameters of Yb3+ in low-symmetry crystalline sites.     

Inert and stable erbium(III)-cored complexes based on metalloporphyrins bearing aryl-ether dendron for optical amplification: synthesis and emission enhancement

We have developed novel inert and stable erbium (Er)(III)-cored complexes based on metalloporphyrins for optical amplification. The functionalized metalloporphyrin ligands have been designed and synthesized to provide enough coordination sites for the formation of inert and stable 9-coordinated Er(III)-cored complexes. Er³⁺ ions were encapsulated by the metalloporphyrin ligands, such as Zn(II)- and Pt(II)-porphyrins. The near-infrared (IR) emission intensity of Er³⁺ ion is much stronger in the Er(III)-cored complex based on Pt(II)-porphyrin than Er(III)-cored complex based on Zn(II)-porphyrin. Furthermore, we have incorporated a G2-aryl-ether functionalized dendron into the Er(III)-cored complex, yielding an Er(III)-cored dendrimer complex bearing the Pt(II)-porphyrin. The Er(III)-cored dendrimer complex shows the stronger near-IR emission intensity than the corresponding complex based on Pt(II)-porphyrin by seven times in solid state. The lifetimes of the emission band of Pt(II)-porphyrin ligands in the visible region were found to be 30 and 40 μs for the Er(III)-cored complex and the Er(III)-cored dendrimer complex based on Pt(II)-porphyrin in deoxygenated THF solution samples, respectively. Also, in both cases, the sensitized luminescence intensity is increased in deoxygenated solution. Therefore, it indicates that the energy transfer from the metalloporphyrins to Er³⁺ ions takes places through the triplet state. In this paper, the synthesis and photophysical properties of novel Er(III)-cored complexes based on metalloporphyrins and Er(III)-cored dendrimer complex based on metalloporphyrin will be discussed.     

FeAl(B2) 合金La, Ac, Sc 和 Y 元素微合金化的第一性原理研究

采用基于密度泛函理论的第一性原理计算方法, 研究了稀土元素(La, Ac, Sc 和 Y) 微合金化对FeAl (B2) 有序金属间化合物合金晶体结构、 弹性和电子性能的影响. 计算结果表明: 稀土元素Y 易于取代Fe位, 而Sc, La和Ac易于取代Al位, 其中Ac元素的加入使晶格点阵发生最大的变形. 弹性性能的计算表明La, Ac, Sc 和 Y 元素的加入可以改善FeAl (B2) 的塑性, 其中Fe₇Al₈Sc具有最好的塑性和硬度. 稀土元素对合金性能的影响, 主要是由于稀土原子的加入改变了Fe和Al电子之间的杂化作用. 计算结果与已有的试验结果和理论结果相一致.