Trivalent Lanthanide Metal Research Articles

Cover Picture: Self‐Assembly of Stereoselective, Mononuclear, Triple‐Stranded Helicate Complexes ML3 with Trivalent Scandium and Lanthanide Metal Ions − Quantitative Transmetallation of the Lanthanide(III) Ion by Sodium(I) Ions (Eur. J. Inorg. Chem. 17/2004)

AbstractThe cover picture shows a stereoselective mononuclear triple‐stranded helicate complex. Three chiral binaphthol N‐oxide derivative ligands are coordinated to a trivalent ytterbium metal atom. This very stable and symmetrical structure was obtained by spontaneous self‐assembly. NMR spectroscopy and X‐ray crystallography were used for unambiguous characterisation. In the picture, the greenish sphere indicates the ytterbium atom and the larger spheres indicate the oxygen atoms. All those ligands, depicted in different shades to highlight the helical effect, are identical. Details are discussed in the article by M. Capó et al. on p. 3405 ff.

Synergistic solvent extraction and separation of trivalent lanthanide metals with mixtures of 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one and aliquat 336

The solvent extraction of La, Nd, Eu, Ho and Lu with 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP) and the quaternary ammonium salt aliquat 336 in the chloride (QCl) and perchlorate (QClO4) forms in CHCl3, CCl4 and C6H12 has been studied. On the basis of the slope analysis, the composition of the extracted species was determined as Q+[LnP4]− (Q+ is the quaternary ammonium salt cation). The values of the equilibrium constant were obtained. The effect of the diluents and the anions of the salt on the metal extraction and separation was determined. The possible interaction between the extractants and its influence on the synergistic extraction process have been discussed.

Surface states and Fermi surface of orderedγ-like Ce films on W(110)

The surface electronic structure of structurally ordered Cerium films deposited on W(110) has been studied along the two surface high-symmetry directions of the close-packed surface. As in other trivalent rare-earth metals a surface state of d z 2-p z symmetry was found to dominate the electronic structure near the Fermi energy. This surface state lies exactly at the Fermi energy at r dispersing towards higher binding energies with increasing wave vector. Its effective mass amounts (-7.4′1.3) times the electron mass. The surface-state induced emission was found to dominate the Fermi-surface cuts near the Γ point of the first surface Brillouin zone (SBZ), while at the Γ point of the second SBZ the surface state lacks intensity.

The design, fabrication and characterization of rare-earth containing multilayer supramolecular films with nanometer-scale controlled composition, structure and properties

We demonstrate the controlled formation of highly-ordered rare-earth stearate multilayer Langmuir–Blodgett films, novel supramolecular organized structures: hybrid polyanion/rare-earth metal cation/anionic surfactant metal–organic superlattice thin films with separating acidic amphiphile bilayers by highly rare-earth-doped polymeric interlayers and fabrication of closely packed, homogeneous and stable rare-earth metal cation/polyanion complex self-assembled multilayer films in which molecular polyelectrolyte building blocks are held together by complexed polyvalent metal cations. The design and fabrication strategies developed to construct those films are based on the surface and interface trivalent rare-earth metal cation complexation with consecutive formation of multilayer superstructures on the solid substrates. The structure and morphology of the built-up multilayer films were characterized by atomic force microscopy and X-ray diffraction.

Chelation Properties of Some Mannich‐Type Polymers Toward Lanthanum(III), Neodymium(III), Samarium(III), and Gadolinium(III)

The chelation behavior of the Mannich‐type polymers, poly[8‐hydroxyquinoline‐5,7‐(piperazine‐N,N′‐diyl‐bismethylene)], polymer I, and poly[8‐hydroxyquinoline‐5,7‐(N,N′‐dimethylethylenediamine‐N,N′‐diyl‐bismethylene)], polymer II, toward the trivalent lanthanide metal ions, La(III), Nd(III), Sm(III), and Gd(III) was studied by a static batch equilibration technique as a function of contact time, pH, and counter ion. The highest metal‐ion uptake of these polymers was achieved at pH≥7.0 and by using perchlorate as the counter ion.

Neue Pnictide im CaAl2Si2-Typ und dessen Existenzgebiet/New Pnictides with the CaAl2Si2 Type Structure and the Stability Range of this Type

Five new compounds were synthesized by heating mixtures of the elements at 600 - 1000 °C and investigated by powder and single crystal X-ray methods. EuMg2P2 (a = 4.280(1), c = 7.164(3) Å), EuMg2As2 (a = 4.393(1), c = 7.321(1) Å),EuMg2Sb2 (a = 4.695(1), c = 7.724(2) Å), YbMg2Sb2 (a = 4.650(1), c = 7.540(2) Å), and SrLiAlSb2 (a = 4.584(3), c = 7.697(9) Å) crystallize with the CaAl2Si2 type structure (P3̄m1; Z = 1). The magnetic susceptibility of EuMg2Sb2 shows Curie-Weiss behavior with an experimental magnetic moment of 7.48(2) μB/Eu atom and a Weiss constant θ = 3.2(1) K. EuMg2Sb2 is ordered antiferromagnetically at 8.2(3) K. Magnetisation measurements at 4.5 K show a linear increase and a saturation for a magnetic moment of 5.9(1) μB/Eu at 5.5 T, indicating an almost parallel spin alignment with increasing field strength. 151Eu Mössbauer spectra at 78 K show an isomer shift of -11.69(5) mm/s, compatible with divalent europium. At 4.2 K we observe full hyperfine field splitting with 23 T. The 121Sb spectrum at 4.2 K shows a transferred hyperfine field of 8(2) T at an isomer shift of -7.9(3) mm/s. From the band structure of EuMg2Sb2 we draw the conclusion, that analogous compounds of trivalent rare-earth metals with CaAl2Si2 type structure should not exist due to electronic reasons.

Oxygen-induced magnetic surface states on the (0001) surfaces of heavy lanthanide metals

Oxygen adsorption on the close-packed surfaces of trivalent heavy lanthanide metals leads to the formation of well-ordered surface-oxide systems. These systems are characterized by fully occupied oxygen-induced surface states, resembling the surface states of the clean metal surfaces. For the magnetic lanthanides, these states exhibit temperature-dependent magnetic splittings with constant finite values above the respective highest magnetic ordering temperatures, ${T}^{*}.$ Angle-resolved photoemission from Gd to Ho reveals a systematic behavior of the splittings: the magnitudes are proportional to the $4f\ensuremath{-}\mathrm{spin}$ moment and their temperature dependencies scale with ${T}^{*}.$

Palladium-Cadmium Ordering In Repdcd (Re = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb) And Comparison With Isotypic Indium Compounds

Abstract Ternary intermetallic compoundsREPdCd (RE=La, Ce, Pr, Nd, Sm, Eu, Tb)were synthesized by reaction of the elements in sealed tantalum tubes in a high-frequency furnace. All compounds were investigated by X-ray diffraction on powders. Those with RE = La, Ce, Pr, Nd, Sm, and Tb contain trivalent rare earth metals and they crystallize with the hexagonal ZrNiAl type structure. NdPdCd [a = 764.8(3), c = 401.3(2) pm] and TbPdCd [a = 756.5(2), c = 389.0(1) pm] are reported here for the first time as well as EuPdCd. The compounds with La, Ce, Pr, and Sm [J. Alloys Compd. 182, 87 (1992)] are confirmed. The crystal structure of EuPdCd was refined from X-ray single crystal diffractometer data: TiNiSi type, Pnma, a = 745.9(3), b = 439.8(2), c = 863.7(3) pm, wR2 = 0.0405, 683 F2 values, and 20 variable parameters. The three-dimensional [PdCd] substructure consists of strongly puckered, orthorhombically distorted Pd3Cd3 hexagons with Pd-Cd distances ranging from 283 to 285 pm. The europium atoms fill the cavities within the [PdCd] network. Chemical bonding in the series REPdCd and REPdIn is compared.

SOLVENT EXTRACTION OF TRIVALENT LANTHANIDES AND YTTRIUM FROM NITRATE MEDIA BY DIALKYL SULPHOXIDES

The solvent extraction of the trivalent rare-earth metals (the lanthanides and yttrium, Ln3+) from nitrate media by xylene solutions of some dialkyl sulphoxides (R2SO, where R=alkyl) was studied. The salting-out effect of added metal nitrate (5.00 M) increases in the order: NH4NO3>NaNO3>LiNO3. Extraction is independent of pH in the range from 2 up to at least 4, but decreases gradually below pH 2 due to the competing extraction of nitric acid. Vapour-pressure osmometry data indicate that the dialkyl sulphoxides are not appreciably self-associated under the conditions studied (0.10 to 0.60M in xylene or toluene solutions at 30°C), which permits the use of organic-phase concentration terms (in place of activities) in the slope-analysis studies. The distribution ratios for the extraction of yttrium, gadolinium and lutetium show a third-order dependence on the concentration of the sulphoxide in the organic phase, with a slightly higher dependence (3.3) for lanthanum. In addition, the mole ratio of nitrate to metal in the loaded organic phase is close to 3, which suggests that the stoichiometry of the extracted complexes is Ln(NO3)3(R2SO)3. Increasing the steric bulk of the substituent alkyl groups (R) in the sulphoxides causes a marked decrease in metal extraction, and a reasonable correlation exists between the extraction of a given metal and the sum of the steric parameters of the alkyl groups in each of the sulphoxides used. In traversing the lanthanide series, the extraction increases in the interval La to Sm, and decreases thereafter to the end of the series. The behaviour of yttrium most closely resembles that of thulium or ytterbium.

Formation of surface intercalation compounds at Gd(Dy)/graphite interfaces under thermal annealing

Angle-resolved valence-band and C 1s core-level photoemission was used to study growth of surface intercalation-like phases upon deposition of trivalent rare-earth metals (Dy and Gd) onto a (0 0 0 1) surface of single-crystalline graphite and highly oriented pyrolytic graphite and subsequent annealing at increasing temperatures, T anneal.. It was found that the synthesis of the surface intercalation compounds ( T anneal.∼1100°C) undergoes a stage of carbide formation ( T anneal.∼900°C). It was concluded that after the high temperature annealing the Gd(Dy)/graphite interfaces reveal layered structure and can be described as thin layers (up to one monolayer) of surface intercalation-like compounds grown on the top of (1 1 1) surfaces of Gd- and Dy-dicarbides.

High pressure phase diagrams of binary lanthanide alloys between La, Ce and Pr

In comparison with the “regular” binary alloy phase diagrams between “regular” trivalent lanthanide metals, binary intralanthanide alloys of Ce exhibit many irregularities typical for Ce under pressure due to its f electron delocalization. For comparison with the La-Ce and Ce-Pr high pressure phase diagrams also the more regular La-Pr data are presented for the pressure range up to 40GPa.

Phase transformations and equation of state of praseodymium metal to 103 GPa

Pressure-induced structural phase transformations in a trivalent rare-earth metal praseodymium (Pr) were studied at room temperature in a diamond anvil cell to 103 GPa by energy dispersive x-ray diffraction using a synchrotron source. Our x-ray diffraction studies document the following crystal structure sequence: $\mathrm{dhc}\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{fc}\stackrel{\ensuremath{\rightarrow}}{c}\mathrm{distorted}\mathrm{}\mathrm{fcc}(hR24\mathrm{type})\ensuremath{\rightarrow}\mathrm{monoclinic}(C2/m)\ensuremath{\rightarrow}\ensuremath{\alpha}\ensuremath{-}$uranium with increasing pressure. We measure a 16.7% volume collapse at the transition to the \ensuremath{\alpha}-uranium phase at 20 GPa. The high-pressure \ensuremath{\alpha}-uranium phase in Pr was found to be stable to the highest pressure of 103 GPa, which corresponds to a volume compression ${V/V}_{0}=0.407.$

Synthesis and Characterization of Novel Metallomesogens: La(Iii), Pr(Iii) and Nd(Iii) Complexes of N-(2-Hydroxy-4-N-Alkoxy-Benzaldehydeimino)-2-Benzamidoethanamide

A novel series of liquid crystalline compounds, N-(2-hydroxy-4-n-alkoxy-benzaldehydeimino)-2-benzamidoethanamide (habbe) (alkyl = octyl, nonyl and decyl), derived from (N-benzoyl)glycylhydrazide, have been synthesized and characterized. Trivalent rare earth metal complexes of the type [Ln(habbe)2Cl2)Cl·2H2O] (where Ln = La(III), Pr(III) and Nd(III)) have been synthesized and characterized by elemental analyses, IR and NMR (1H and 13C) spectral studies. The coordinating behaviour of the liquid crystalline habbe series towards the lanthanide metal ions were studied by IR and NMR spectral techniques. Further, the preliminary studies of thermal microscopy (TM) (polarizing microscope with a hot stage) and differential scanning calorimetry (DSC) confirm the presence of liquid crystalline phases in the present series of habbe derivatives and their complexes. IR and NMR spectral data strongly suggest a neutral tridentate behaviour of the mesogen ligands in the complexes.

Tridentate binding units as structural patterns for the design of nine-coordinate lanthanide building blocks with predetermined properties

The use of rigid receptors displaying preorganized cavities for the selective complexation of spherical ions has shown some limitations for trivalent lanthanide metal ions, Ln III, because of the minor variation of their ionic radii. The recent development of semi-rigid ligands derived from macrocyclic platforms grafted with complexing pendant arms or from tripodal podands leads to an unprecedented fine tuning of the structural, thermodynamic and electronic properties of the lanthanide complexes, thus opening new perspectives for the design of functional molecular or supramolecular devices. The application of the Induced fit concept for the design of covalent and non-covalent nine-coordinate monometallic and polymetallic podates is emphasized together with applications as light-converters, thermal and electrochemical switches and template agents. The step-by-step evolution from rigidity to flexibility in lanthanide coordination chemistry is presented and the basic recognition processes responsible for the tuning of the metallic site are discussed.

Chelation Properties of Poly(8–Hydroxyquinoline 5,7–diylmethylene) Crosslinked with Bisphenol–A Toward Lanthanum(III), Cerium(III), Neodimium(III), Samarium(III), and Gadolinium(III) Ions

The chelation behavior of poly(8–hydroxyquinoline 5,7–diylmethylene) crosslinked with various amounts of bisphenol–A toward some trivalent lanthanide metal ions, such as La(III), Ce(III), Nd(III), Sm(III), and Gd(III), has been investigated by a static batch equilibration technique. The effects of crosslinking on the chelation characteristics of these resins were studied. The optimal capacity of metal-ion uptake was achieved by incorporating 5–10% of bisphenol–A into the polymer matrix. A scanning electron microscope was used to analyze the surface morphology of the polymers. The measured water-regain values have shown that the hydrophilicity of the crosslinked polymers increases as the degree of crosslinking is increased.

Determination of Stability Constants of Metal Complexes by Capillary Electrophoresis

The stability constants of several divalent first row transition and trivalent lanthanide metal complexes were determined by capillary electrophoresis (CE) methods. Four different approaches, i.e. direct formation, ligand exchange, metal exchange and metal-ligand double exchange were developed. To verify if these CE methods are indeed applicable, the stability constant of CuHEDTA was re-determined to be 17.47 ± 0.20 (consistent with the published 17.50) using the CuEDTA and ZnHEDTA metal-ligand double exchange approach. The stability constants of lanthanide (Ce3+ and Eu3+) and transition metal (Ni2+ and Zn2+) complexes of an aminopolycarboxylate ligand, DO2A (1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane) were measured under the direct complex formation condition. The stability constant of the NiDO2A complex was determined by the ligand exchange method using 1,4,8,11-tetraazaundecane (2,3,2-tet) as the competing ligand. The stability constant of CuDO2A complex was determined by the metal exchange method using Zn2+ ion as the competing metal ion, and complex formation competitions of Ni2+ and Cu2+ between DO2A and 2,3,2-tet were studied by the metal-ligand double exchange method. Effects of experimental conditions and the advantages and limitations of these CE methods are discussed.

Ion-Exchange Equilibria between Some Rare Earth Metal Ions and Hydrogen Ions in Iron(III) and Tin(IV) Antimonates as Cation Exchangers

Ion-exchange equlibria of trivalent rare earth metal ions (Eu3+, Gd3+, and Tm3+)/H+systems were studied at 25, 35, and 50 ± 1°C on FeSb and SnSb as cation exchangers. The exchange isotherms were measured for both forward and reverse reactions with a solution of ionic strength 0.1 by the batch technique. Selectivity coefficients (log scale) varied with the equivalent fraction (X̄M) of rare earth metal ions in the exchanger and gave a linear function againstX̄Min the range 0.5 to 1. The selectivity sequence on zero loading is Tm3+< Gd3+< Eu3+for both exchangers. The overall thermodynamic data are evaluated.

Surface electronic structure of epitaxial Ce and La films

We report on a detailed photoemission (PE) study of monocrystalline Ce and La metal films grown on W(110). Angle-resolved PE reveals that both systems have very similar valence-band structures, with the observed dispersions being in good agreement with local-density approximation band-structure calculations. These calculations were performed for three different close-packed crystal structures of La and Ce metal, giving evidence for a double hcp structure of the films, i.e., a $\ensuremath{\beta}$ phase in the case of Ce. The pronounced surface state, characteristic for the close-packed surfaces of trivalent lanthanide metals, is shown to exist also for $\ensuremath{\beta}$-Ce(0001), extending over a wide range of the surface Brillouin zone. The 4$f$ electronic structure of the Ce film was studied by resonant PE at the 4$\stackrel{\ensuremath{\rightarrow}}{d}4f$ threshold. A separation of bulk and surface contributions with high resolution was achieved by quenching the surface signal with a Dy overlayer. In this way, a surface shift of (140$\ifmmode\pm\else\textpm\fi{}$40) meV of the ${4f}^{0}$ final state emission was found for $\ensuremath{\beta}$-Ce, which is discussed in connection with $f\ensuremath{-}d$ hybridization.

Synthesis and Spectral Characterization of Some Deprotonated Rare Earth Metal Complexes

Trivalent rare earth metal complexes of N-(3,4-diaminobenzophenonimino)-2-benzamidoethanamide (Hdabbe) of the type [Ln(dabbe)2OH(H2O)2], where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Y, have been synthesized and characterid by elemental analyses, electrical conductance, magnetic susceptibility, electronic, IR and NMR (1H, and 13C) spectral techniques. The bonding parameters β, b1/2, % δ and η were calculated from the electronic spectral bands of the Pr(III), Nd(III), Sm(III) and Dy(III) complexes and suggest weak covalent bond formation in the complexes. The theoretical oscillator strengths (Pcalcd) calculated from the Judd-Ofelt equation were found to be in reasonable agreement with the experimental values. The IR and NMR spectral data suggest a uninegative bidentate nature of Hdabbe in the complexes.

SYNERGISTIC EFFECTS IN SOLVENT-EXTRACTION SYSTEMS BASED ON ALKYLSALICYLIC ACIDS. IV. EXTRACTION OF THE TRIVALENT RARE-EARTH METALS IN THE PRESENCE OF BIFUNCTIONAL C=0, P=0 AND S=0 COMPOUNDS

ABSTRACT Several bifunctional compounds of different types (diamides, diphosphonates and disulphoxides) were synthesized, and their effect on the extraction of the trivalent rare-earth metals from chloride media by solutions of some alkylsalicylic acids (HA) in xylene was investigated. Appreciable synergistic shifts in the individual pH50 values were observed in most cases, the shifts generally increasing in the order S=0 ≤ C=0 < P=0 for comparable bifunctional compounds containing these donor groups. For compounds with C=0 or P=0 groups, the synergism is greater when the two groups are separated by a one-carbon bridge (-CH2-) than by a two-carbon bridge (-CH2-CH2-), whereas the opposite is true for compounds containing S=0 groups. For a given bifunctional compound, the synergistic shifts were found to increase with increasing steric bulk of the alkylsalicylic acid The synergistic shifts produced by the addition of a given bifunctional compound generally decrease across the lanthanide series (La to Lu), which suggests that coordination of the neutral ligand is somewhat dependent on steric factors. For the diamides and diphosphonates containing a -CH2- bridge, the synergistic effects in the extraction of neodymium (and lanthanum) are substantially greater than for their monofunctional analogues, which suggests that these bifunctional compounds may be coordinated to these metals in a bidentate mode. Slope analysis studies and measurements of the solubility of the neodymium-alkylsalicylic acid complex in xylene solutions of the bifunctional ligands (L) are consistent with the formation of complexes of stoichiometry NdA3L.