L.B Zinner

Luminescence and structure of europium compounds

Abstract Europium complexes in the +3 oxidation state, with coordination numbers six, seven, eight, nine and ten are under consideration. In most cases, single crystals or isomorphous compounds were studied by X-ray structural analyses. An attempt is made to correlate the results with the emission spectrum interpretation. Only articles containing both aspects are included in this review. Some general remarks concerning different coordination numbered complexes are also presented.

Synthesis and structure of lanthanide picrates with trans-1,3-dithiane-1,3-dioxide

Abstract Compounds with the formula [Ln(pic) 3 ( trans -DTSO 2 ) 2 ] (Ln=La–Lu and Y) were obtained by reaction of hydrated lanthanide picrates with trans -1,3-dithiane-1,3-dioxide ( trans -DTSO 2 ) in absolute ethanol. Lanthanide contents were determined by titration with EDTA; CHN were determined by microanalytical procedures. Data are in good accordance with the proposed stoichiometry. IR absorption spectra were interpreted in terms of trans -DTSO 2 and picrate anions coordinated through the oxygen atoms. The parameters obtained from the absorption spectrum of the Nd(III) compound indicate weakly covalent metal–ligand bonds. The emission spectrum obtained at 77 K for the Eu(III) compound suggests a C 2v symmetry for the coordination polyhedron. X-Ray powder patterns show that the compounds are isomorphous. The structure of europium compound was determined by single crystal X-ray analysis and showed that the crystals are triclinic, space group P 1 , a =10.771(1) A, b =12.243(1) A, c =16.415(2) A, α =99.930(10)°, β =103.970(10)°, γ =106.220(10)°. The compound exhibits a polymeric structure, in which two trans -DTSO 2 are bridging the Eu(III) ions. The central ion is octacoordinated to four oxygens of trans -DTSO 2 and four oxygens of one bidentate and two monodentate picrate anions, in a bicapped trigonal prism geometry, the dihedral angle between the bases being 14.2(1) o .

Studies of neodymium, europium and terbium picrate complexes with benzyl-t-butyl sulphoxide

Abstract Complexes of the formula Ln(pic) 3 ·4L (Ln  Nd, Eu, Tb; pic, picrate; L, benzyl- t -butylsulphoxide) were obtained either by precipitation by ligand addition to a hot aqueous solution of the lanthanide salt or by simply melting a mixture of components (“one-pot” synthesis). The compounds were characterized by Ln titration with EDTA, C, H and N elemental analysis, IR spectra, absorption spectra of the neodymium compound, emission spectra of the europium compound and thermal analysis.

Uranyl nitrate complexes with lactams

Abstract The preparation, characterization and spectroscopy of complexes of uranyl nitrate with the lactams: δ-valerolactam (δ-val, C 5 H 9 NO), e-caprolactam (e-capro, C 6 H 11 NO), 2-azacyclononanone (2-aza, C 8 H 15 NO) and 2-azacyclotridecanone (2-actd, C 12 H 23 NO) are described. They were prepared by reaction of hydrated uranyl nitrate with the ligands in ethanolic solution (molar ratio 1:2) and presented the general composition UO 2 (NO 3 ) 2 .2L, except for the e-capro complex that is dimeric, with composition: (UO 2 ) 2 (NO 3 ) 2 (O 2 )(e-capro) 4 . The peroxo bridge was introduced when 2,2-dimethoxypropane contaminated with peroxide was used to precipitate the crystals. They were characterized by CHN microanalyses, IR spectra, TG and DSC analyses and emission spectra in the visible region. The structure of the e-capro complex was determined by X-ray single crystal analysis.

Structures of the anhydrous Yb(III) and the hydrated Ce(III), Sm(III) and Tb(III) methanesulfonates

Abstract The methanesulfonates of trivalent lanthanides, Ln(CH3SO3)3·xH2O (Ln=Ce, Sm and Tb with x=2 and Ln=Yb with x=0), have been prepared by the reaction of methanesulfonic acid with the respective lanthanide oxide (CeO2, Sm2O3 Tb4O7 and Yb2O3) in the presence of water. In the reactions involving cerium and terbium oxides, hydrogen peroxide was used as reducing agent. Single crystals, suitable for X-ray examination, were obtained by slow evaporation of water-ethyl alcohol (50:50, v/v) solution. The isostructural tris(methanesulfonate)dihydrates of the trivalent Ce, Sm and Tb crystallize in the monoclinic system, space group P21 /c (14), with Z=4, and cell parameters: a=948.9(l); b=1431.9(2); c=983.7(l) pm, β=91.22(2)° for Ce; a=938.1(l), b=1417.9(2), c=974.3(3) pm, β =91.19(2)° for Sm; and a=931.3(3), b = 1407.2(3), c=966.4(3) pm, β=91.09(3)° for Tb. Also the water-free ytterbium compound crystallizes in the monoclinic system, however the space group is P21 (4), with two molecules per elementary cell. Its crystallographic parameters are a=979.8(5), b = 509.4(2), c=l 183.7(5) pm and β= 107.16(4)°. In all investigated compounds the methanesulfonate anion acts as a bidentate ligand, bridging two metallic centers to yield polymeric structures.

Catalytic activity of lanthanide-doped Y zeolite on the alkylation of benzene with 1-dodecene model reaction

Abstract Rare earth doped Y zeolites, RE,Ca:NaY (RELa, Ce, Nd or Gd), were synthesized by the ion exchange method. Thermal treatment and activation suggest that the rare earth hydroxyl cations play an important role in the catalytic activity of the Y zeolite on the alkylation of benzene with 1-dodecene model reaction. Special emphasis is placed on the activity and selectivity of the alkylation and the extent of the isomerization reactions.

Crystal structures, spectroscopic, TG and DSC studies of lanthanide picrate complexes with 4-methylmorpholine N-oxide (MMNO)

Abstract The crystal structures, IR absorption spectra, emission spectrum of the europium compound, TG and DSC analyses of Ln(pic) 3 ·MMNO·2H 2 O (pic=picrate, Ln=La, Nd, Eu) complexes are reported. The crystals that were grown from methanolic solutions, are isomorphous belonging to the triclinic space group P 1. The Ln ions are coordinated to nine oxygen atoms, six of the picrate moieties, one of the MMNO and two of water molecules, giving rise to a tricapped trigonal prism.

Structure and properties of hydrated La(III), Nd(III) and Er(III) methanesulfonates

Detailed investigations of the methanesulfonates of neodymium and erbium presented in this work show that they have the same kind of structure as the dihydrated cerium, samarium and terbium methanesulfonates, while the lanthanum compound exhibits a very unusual structure with water molecules bridging two metallic centers. The study of the far infrared spectra of the La(III) to Lu(III) compounds in the 700-50 cm -1 range has been shown to be a useful tool for the indirect investigation of the structure of these kind of compounds. Thermal analyses indicate loss of water at temperatures of 100-200°C, giving origin to the respective anhydrous salts, stable up to ∼400°C. The final residues are oxosulfates.

Tetramethylurea adducts of the tricyclopentadienyl lanthanide complexes

Abstract The tetramethylurea adducts of tricyclopentadienyl lanthanide(III) complexes, Cp3Ln·TMU (Ln = La, Ce, Nd, Sm, Eu and Yb, TMU = 1,1,3,3-tetramethylurea), have been isolated by addition of the stoichiometric amount of (CH3)2NCON(CH3)2 to Cp3Ln·THF, in hexane. The compounds were characterized by standard techniques and the molecular structures of Cp3Ce·TMU and Cp3Nd·TMU were determined by single crystal X-ray diffraction analysis. The two compounds are isomorphous. The metal centre is tetrahedrally coordinated.

Separation of samarium and gadolinium solutions by solvent extraction

Abstract Interest in the production of individual rare earth (RE) elements has increased in the last years, due to the advances in technological applications of RE. Samarium and gadolinium are used in several applications: nuclear industry, lasers, supermagnets among others. This paper presents a technological contribution to the study of RE separation, in order to obtain Sm and Gd concentrated solutions. Experiments were carried out on a laboratory scale using solvent extraction techniques. Separation of Sm and Gd is studied in a continuous system in a micropilot unit of mixer-settlers. The extractant used is 2-ethylhexyl phosphonic acid, mono-2-ethylhexyl ester, diluted in isododecane (1 M). The aqueous phase processed was a chloride solution of medium and heavy RE produced from monazite leaching. The RE determinations in aqueous solutions were performed using an atomic emission spectrometer with inductively coupled plasma Aton-Comp, serial Ash-800. The analytical results are presented as RE concentrations profiles. Two continuous-circuit configurations are described of extraction-scrubbing-stripping for the production of Sm and Gd concentrated solutions with purity higher than 90% and 94%, respectively.