Synthesis and study of rare-earth uranogermanates

A series of M^III(HGeUO₆)₃ · 8H₂O rare-earth uranogermanates (M^III = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er) were prepared by precipitation from solutions under hydrothermal conditions. The compositions and structures of the synthesized compounds were studied, their complete crystallographic and functional similarity were established, and the processes of their dehydration and thermal decomposition were studied on the basis of chemical analysis, X-ray diffraction, IR spectroscopy, and differential scanning calorimetry data.     

Flame-ion chemistry of the lanthanide metals Ce,Pr and Nd

A pair of premixed, H₂O₂Ar flames of fuel-rich (FR) and fuel-lean (FL) composition, both at atmospheric pressure and 2425 K, were doped with about 10⁻⁶ mol fraction of the lanthanide metals La, Ce, Pr and Nd; from a previous study, La was used as a benchmark. The metals produce solid particles in the flames and gaseous metallic species. The latter include metallic atoms A near the flame reaction zone, but only the monoxide AO, the oxide hydroxide OAOH and, in some cases, the dioxide AO₂ further downstream at equilibrium. Metallic ions (< 1% of the total metal) were observed by sampling the flames through a nozzle into a mass spectrometer. All of the observed ions can be represented by four hydrate series: (a) major signals of AO⁺·nH₂O (n = 0–3) for La, Ce, Pr and Nd; (b) small signals of AO₂H⁺·nH₂O (n = 0–2) for Ce, Pr and Nd; (c) still smaller signals of AO₂⁺·nH₂O (n = 0, 1) for Ce, Pr and Nd in the FL flame only; and (d) tiny signals of AOH⁺·nH₂O (n = 0, 1) for Pr and Nd in the FR flame only. The actual structures of some of these ions may not correspond to simple hydrates: e.g. AO⁺·H₂O = A(OH)₂⁺ = protonated OAOH; AO₂H⁺·H₂O = A(OH)₃⁺, etc. Since hydrogen flames contain essentially no natural ionization, a major objective was to consider probable ionization mechanisms for the metals. The primary reactions include both chemi-ionization, and thermal (collisional) ionization of AO whose ionization energy is low (about 5 eV). Some of the ions are formed by secondary ion/molecule reactions including three-body hydration, proton transfer, electron (charge) transfer, H atom abstraction by radicals and oxidation. In addition, the chemical ionization of the metallic species by H₃O⁺ was investigated. The flame-ion chemistry of these metals is discussed in detail.     

Magneto,spectral and thermal studies of lanthanide perchlorato complexes of 5,6-benzoquinoline

A new series of complexes of 5,6-benzoquinoline (Benzqn) with lanthanide perchlorates with the general composition Ln(ClO₄)₃·7Benzqn (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy or Ho) were synthesised and characterised by elemental analysis, conductance, molecular weight and infrared spectra. The thermal behaviour of these complexes have also been studied.     

Raman active normal vibrations of lanthanide oxychlorides

Raman spectra of solid state lanthanide oxychlorides, LnOCl, where Ln  La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er, have been measured in the 1000-40 cm⁻¹ region and the observed fundamental wavenumbers have been assigned and discussed by referring to the results of the factor group analysis and the normal coordinate calculations based on a tetragonal space group D⁷_4h.     

Synthesis and study of polyuranates MIIIU3O10.5·6H2O (MIII = La, Ce, Pr, Nd, Sm)

Previously unknown individual crystalline compounds M^IIIU₃O_10.5·6H₂O were obtained by the reaction of synthetic schoepite UO₃·2.25H₂O with aqueous solutions of La, Ce, Pr, Nd, and Sm nitrates in hydrothermal conditions at 200°C. Their composition and structure were determined, and the processes of dehydration and thermal decomposition were studied by the methods of chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.     

Chelation behaviour of lanthanons witho-arsonodibenzoylmethanephenylhydrazone

Summary The chelate formation reaction of La(III), Pr(III), Nd(III), Gd(III), Ho(III), and Er(III) witho-arsonodibenzoylmethanephenylhydrazone has been investigated potentiometrically and conductometrically in 40% (v/v) aqueous ethanol, ionic strength 0.1M. The order of stability constants was found to be La < Pr < Nd > Gd < Ho < Er. The chelates formed have 1:1 and 1:2 stoichiometries (M ³⁺:L). The complexes have been isolated in solid state and have been characterized on the basis of elemental analysis and IR data. Coordination occurs through -NH of the hydrazo and-OH of the arsonic groups.

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Chelierungsverhalten von Lanthaniden mito-Arsonodibenzoylmethanphenylhydrazon

Zusammenfassung Die Reaktion der Chelatbildung von La(III), Pr(III), Nd(III), Gd(III), Ho(III) und Er(III) mito-Arsonodibenzoylmethanphenylhydrazon wurde potentiometrisch und konduktometrisch in 40% (v/v) wäßrigem Ethanol bei einer Ionenstärke von 0.1M untersucht. Die Reihung der Stabilitätskonstanten war La < Pr < Nd > Gd < Ho < Er. Die Chelate haben 1:1 und 1:2 Stöchiometrien (M ³⁺:L). Die Komplexe wurden im Festzustand isoliert und mittels Elementaranalyse und IR-Spektroskopie charakterisiert. Die Koordinierung erfolgt über -NH der Hydrazo- und -OH der Arsongruppe.

     

Spectrophotometric study of rare-earth element complexation in alkaline and near-neutral solutions

The hydrolytic behavior of La, Nd, Eu, Gd, Ho, and Tm in KOH solutions was studied at 25°C and a saturated vapor pressure using spectrophotometry with m-cresol purple and 2-naphthol as pH indicators. It was found that freshly prepared solutions of MCl₃ (M = La, Nd, Eu, Gd, Ho, and Tm) at pH 6.0–10.1 contain the ions M³⁺, M(OH)²⁺, M(OH) ₂ ⁺ , and M(OH) ₃ ⁰ , for Ho and Tm, the complex anions M(OH) ₄ ^? . were also detected. The formation constants of the hydroxide complexes a ionic strengths I = 0 were obtained as the parameters of linear regression equations that characterize the spectra of the indicators in the solutions under study.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

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Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Decay studies of 143La and 147Pr

The decay properties of ¹⁴³La and ¹⁴⁷Pr were investigated with Ge(Li), NaI(Tl) and plastic detectors in singles and coincidence modes with the help of a rapid paper electrophoresis. Twenty-three new γ-rays for ¹⁴³La and 9 new transitions for ¹⁴⁷Pr were observed and fairly precise decay schemes for ¹⁴³La including 5 new levels and for ¹⁴⁷Pr including 4 new levels were proposed. The half-lives of ¹⁴³La and ¹⁴⁷Pr are 14.14 ± 0.16 and 13.3 ± 0.4 min, and observed Q_β values for ¹⁴³La and ¹⁴⁷Pr are 3.28 ± 0.10 and 2.77 ± 0.10 MeV, respectively.     

Research of thermal decomposition of hydrated methanesulfonates

Hydrated methanesulfonates Ln(CH₃SO₃)₃·nH₂O (Ln=La, Ce, Pr, Nd and Yb) and Zn(CH₃SO₃)₂·nH₂O were synthesized. The effect of atmosphere on thermal decomposition products of these methanesulfonates was investigated. Thermal decomposition products in air atmosphere of these compounds were characterized by infrared spectrometry, the content of metallic ion in thermal decomposition products were determined by complexometric titration. The results show that the thermal decomposition atmosphere has evident effect on decomposition products of hydrated La(III), Pr(III) and Nd(III) methanesulfonates, and no effect on that of hydrated Ce(III), Yb(III) and Zn(II) methanesulfonates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Facile sonochemical synthesis and photoluminescent properties of lanthanide orthophosphate nanoparticles

Uniform lanthanide orthophosphate LnPO₄ (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) nanoparticles have been systematically synthesized via a facile, fast, efficient ultrasonic irradiation of inorganic salt aqueous solution under ambient conditions without any surfactant or template. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL) spectra as well as kinetic decays were employed to characterize the samples. The SEM and the TEM images show that the hexagonal structured lanthanide orthophosphate LnPO₄ (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd) products have nanorod bundles morphology, while the tetragonal LnPO₄ (Ln=Tb, Dy, Ho) samples prepared under the same experimental conditions are composed of nanoparticles. HRTEM micrographs and SAED results prove that these nanostructures are polycrystalline in nature. The possible formation mechanism for LnPO₄ (Ln=La-Gd) nanorod bundles is proposed. Eu³⁺-doped LaPO₄ and Tb³⁺-doped CePO₄ samples were also prepared by using the same synthetic process, which exhibit an orange-red (Eu³⁺:⁵D₀-⁷F_{1, 2, 3, 4}) and green (Tb³⁺, ⁵D₄-⁷F_{3, 4, 5, 6}) emission, respectively.     

Regularities of change in the structural parameters of EuLnCuS<Subscript>3</Subscript> (Ln = La–Nd,Sm, Gd,Ho)

Regularities of change in the structural parameters of EuLnCuS₃ (Ln = La–Nd, Sm, Gd, Ho) at an annealing temperature of 970 and 1170 K have been established. A decrease in the Ln³⁺ ionic radius results in the consecutive change of structural types (STs) for the compounds: α-EuLnCuS₃ (Ln = La, Ce, Pr, Nd; BaLaCuS₃ ST) → β-EuLnCuS₃ (Ln = Ce, Pr, Nd; Ba2MnS₃ ST) → γ-EuLnCuS₃ (Ln = Sm, Gd, Ho; Eu₂CuS₃ST). The change of structural types for EuLnCuS₃ leads to a jump-like change in their unit cell parameters and the transformation of coordination polyhedra shaped as a one-capped trigonal prism LnS₇ (α and β phases) into an octahedron LnS₆ (γ phases). The appearance of morphotropic changes correlates with the tetrad effect.     

Thermal decompositions of lanthanum and lanthanide salts of sebacic acid

The conditions of thermal decomposition of La, Ce(III), Pr(III), Nd, Sm(III), Eu, Gd, Tb(III), Dy, Ho, Er, Tm, Yb and Lu sebacates have been studied. When heated in air atmosphere, the sebacates of La and lanthanides with general formula Ln₂(C₁₀H₁₆O₄)₃·nH₂O, wheren=6?24, lose some crystallization water molecules in one or two steps at 323–343 K and are then dehydrated and decomposed simultaneously to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The oxides are formed over the range of temperature 783 K (CeO₂)?1073 K (Nd₂O₃).     

A study of lanthanide p-toluene sulphonic acid complexes in solution

Lanthanide p-toluene sulphonic acid (ptsa) complexes were prepared for La, Pr, Nd, Sm, Eu, Dy, Ho, Er and Yb, and found to exist as Ln(ptsa)₃. Conductivity studies of La(ptsa)₃ in DMSO and DMF suggest 1:2 and, possibly, 1:1 electrolyte behaviour in these solvents, respectively. NMR lanthanide-induced chemical shifts (LIS) for aromatic protons in (ptsa)^? and methyl protons in DMSO, were measured for all complexes as a function of the [Ln³⁺[DMSO] in a medium consisting of CCl₄, DMSO, and CH₃CN. Analysis of the LIS data suggests a change in (ptsa)^? coordination round Ln₃₊ across the lanthanide series.     

Potentiometric studies on the complexation equilibria between La(III), Pr(III), Nd(III), Gd(III), Sm(III), Tb(III), Dy(III), Ho(III) and 2-acetylpyridinethiosemicarbazone (2-apt)

Complex formation between trivalent La, Pr, Nd, Gd, Sm, Tb, Dy, Ho and 2-acetylpyridinethiosemicarbazone has been investigated by potentiometric measurements at 25°C and in 0.02 M, 0.05 M, 0.1 M and 0.2 M (NaClO₄) ionic strengths. The stability constants of the complexes formed have been determined and correlated to the size and ionic potentials of the metal ions.     

Ln3UO6Cl3 (Ln=La,Pr, Nd) -. Die ersten Oxochlorouranate der Seltenen Erden

Ln₃UO₆Cl₃ (Ln=La, Pr, Nd) — The First Oxochlorouranates of the Rare Earths . The new compounds Ln₃UO₆Cl₃ (Ln=La, Pr, Nd) were prepared by heating stoichiometric amounts of LnOCl/Ln₂O₃/U₃O₈ (7 : 1 : 1) (Ln=La, Nd) and PrOCl/Pr₆O₁₁/U₃O₈ (12 : 1 : 2) in silica ampoules (5 d, 1000°C, Ln=La; 9 d 800°C, Ln=Pr, Nd) in the presence of an excess of chlorine [p(Cl₂, 25°C)=1 atm]. Single crystals were obtained by chemical transport reactions using chlorine [p(Cl₂, 25°C)=1 atm] as transport agent [T₂=1000°C→T₁=900°C (Ln=La); T₂=840°C→T₁=780°C (Ln=Pr, Nd)]. Crystals of Ln₃UO₆Cl₃ (Ln=La, Pr, Nd) were investigated by X-ray diffraction methods and La₃UO₆Cl₃ additionally by high resolution electron microscopy. The compounds Ln₃UO₆Cl₃ crystallize in the hexagonal spacegroup P6₃/m (No. 176) with Z=2 formula units per unit cell. Isotypical structure refinements resulted in R=3.04% respectively R_w=1.91% (Ln=La), R=4.72% respectively R_w=3.80% (Ln=Pr) and R=3.99% respectively R_w=2.49% (Ln=Nd). Uranium is coordinated with six oxygen atoms forming a trigonal prism. Lanthanide ions are 10-coordinated (6 oxygen atoms, 4 chlorine atoms).     

Thermodynamic investigation of the phase formation processes in the systems LnSe2–LnSe1.5 (Ln = La,Ce, Pr,Nd)

The pressure of selenium was measured by the static method with quartz membrane-gauge manometers in the systems LnSe₂–LnSe_1.5 (Ln = Ce, Pr) within the temperature range (893–1332) K. From p_Se-T-x dependences obtained, the composition of intermediate phases and the thermodynamic characteristics (Δ_rH₂₉₈, Δ_rS°₂₉₈) for the stepwise dissociation processes in the systems studied were calculated. Data obtained in our previous works for the systems LnSe₂–LnSe_1.5 (Ln = La, Pr, Nd) were reprocessed in connection with more correct estimation of heat capacities and absolute entropies of polyselenides. The standard thermodynamic functions (Δ_fH₂₉₈, S°₂₉₈, Δ_fG°₂₉₈) of La, Ce, Pr, Nd polyselenides were determined. Solid phase compositions in the systems LnSe₂–LnSe_1.5 (Ln = La, Ce, Pr, Nd) may be described by general formula Ln_nSe_2n−1 (n = 5, 7, 10, 20). The dependence of thermodynamic values of polyselenides on the selenium content was analysed. The set of thermodynamic characteristics obtained may be used for phase equilibria calculation and for thermodynamic modelling of single-crystal growth processes in the systems LnSe₂–LnSe_1.5 (Ln = La, Ce, Pr, Nd).     

Measurement of K β /K α intensity ratios for elements in the range 51 ≤ Z ≤ 67 at 59.54 keV

K-shell X-ray intensity ratios for some elements Sb, Cs, La, Ce, Pr, Nd, Sm, Gd, Dy and Ho have been measured experimentally. The elements were excited by 59.5 keV γ-ray from 100 mCi ²⁴¹Am radioactive source. The characteristic K X-rays emitted by samples were detected by using a hyper pure germanium detector. The experimental results were compared with theoretical predictions reported by several authors.     

Synthesis, identification and thermal decomposition of double sulfates of La, Ce, Pr or Nd with ethanolammonium

On evaporation at room temperature of an aqueous reaction mixture of Ln(III) sulfate and ethanolammonium sulfate in a molar ratio higher than 1∶16, crystal products with a waxy feel were obtained. They were identified by means of the X-ray powder diffraction patterns and it was concluded that they are isostructural. The results of elemental analysis and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH₂CH₂NH₃)₄Ln₂(SO₄)5·4.5H₂O (Ln=La, Ce, Pr or Nd) Their thermal decompositions in static atmosphere in the temperature range from ambient up to 1173 K took place in a similar way, and mainly Ln₂O₂SO₄ was obtained as final product. The exception was the Ce compound, which decomposed to CeO₂. The double sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of thermal decomposition was presumed. The X-ray powder diffraction patterns of Ln₂O₂SO₄ (Ln=La, Pr and Nd) show that they are also isostructural.     

Syntheses,characterization, and crystal structures of coordination polymers: {NH4 · [Ln(OVA)4]} n (Ln=Pr,Nd, Gd,and Ho; OVA=2-hydroxy-3-methoxybenzoate)

The title complexes {NH₄ · [Ln(OVA)₄]} _n (Ln = Pr, Nd, Gd, and Ho; OVA = 2-hydroxy-3-methoxybenzoate) were synthesized in water and characterized by FT-IR, elemental analysis, TGA, and X-ray single-crystal diffraction analysis. Two distinct structure types were isolated. Structure type I with formula {NH₄ · [Ln(OVA)₄]} _n (Ln = Pr, Nd, Gd) contains Ln–COO^? quadruply-bridged helical 1-D chains, with all carboxylates bridging. The structure type II with formula {NH₄ · [Ho(OVA)₄]} _n contains bridging and chelating carboxylates, resulting in Ho–COO^? double helical 1-D chains. The passage from type I to type II structure is ascribed to the lanthanide contraction. These 1-D chains are extended to 3-D supramolecular architecture by hydrogen bonds.