Die Kristallstrukturen von KNdTe4, RbPrTe4 und RbNdTe4 — Untersuchungen zur thermischen Stabilität von KNdTe4 sowie Bemerkungen zu einigen anderen Vertretern der Zusammensetzung ALnTe4 (A = K,Rb, Cs und Ln = Seltenerd‐Metall)

Crystal Structures of KNdTe₄, RbPrTe₄, and RbNdTe₄ — Investigations concerning the Thermal Stability of KNdTe₄ as well as some Remarks concerning Additional Representatives of the Composition ALnTe₄ (A = K, Rb, Cs and Ln = Rare Earth Metal) Of the compounds ALnQ₄ (A = Na, K, Rb, Cs; Ln = Lanthanoid; Q = S, Se and Te) the crystal structures of the three new tellurides KNdTe₄, RbPrTe₄ and RbNdTe₄ were determined by X‐ray single‐crystal structure analysis and of the three additional new ones KCeTe₄, KPrTe₄ and CsNdTe₄ by X‐ray powder diffraction experiments. All six new compounds are isotypic with KCeSe₄. Characteristic for the crystal structure of the compounds mentioned above are layers built from (Q₂)^2— dumbbells in form of 4.3².4.3 nets with embedded cations A⁺ and Ln³⁺ between them, which are coordinated eightfold in form of square‐shaped antiprisms by Q ions. The distances Te‐Te within the dumbbells were found to be 277.8(2) pm for all investigated tellurides. By combination of X‐ray diffraction and DTA measurements it was shown that the compound KNdTe₄ is metastable at ambient temperature with a limited existence range between the temperatures 260 and 498 °C.     

Synthesis and luminescence studies on lanthanoid(III) complexes of aSchiff base derived from 2-acetylpyridine andtris-(2-aminoethyl)-amine

Summary A potentially heptadentated ligand (apytren) was obtained by condensation of 2-acetylpyridine andtris-(2-aminoethyl)-amine in the presence of lanthanoid(III) cations. Complexes of the formulaLn(apytren)(NO₃)₃·H₂O (Ln=La, Eu, Gd, and Tb) have been isolated and characterized, both in the solid state and in solution, by means of vibrational and electronic spectroscopy and of conductometric measurements. Their photophysical properties, including emission quantum yields and lifetimes, were studied and are discussed.

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Synthese und Lumineszenzuntersuchungen an Lanthanoid(III)-Komplexen mit einer aus 2-Acetylpyridin undtris-(2-Aminoethyl)-amin hergeleitetenSchiffschen Base

Zusammenfassung Durch Kondensation von 2-Acetylpyridin undtris-(2-Aminoethyl)-amin in der Gegenwart von Lanthanoid(III)-Kationen wurde ein potentiell siebenzähniger Ligand (apytren) erhalten. Komplexe der ZusammensetzungLn(apytren)(NO₃)₃·H₂O (Ln=La, Eu, Gd und Tb) wurden isoliert und sowohl im festen Zustand als auch in Lösung mittels IR-und UV-Vis-Spektroskopie und Leitfähigkeitsmessungen charakterisiert. Ihre photophysikalischen Eigenschaften, einschließlich Emissionsquantenausbeute und Lebensdauer, wurden untersucht und werden diskutiert.

     

A combination of quasirelativistic pseudopotential and ligand field calculations for lanthanoid compounds

Summary Improved energy-adjusted quasirelativistic pseudopotentials for lanthanoid atoms with fixed valency are presented and tested in molecular calculations for CeO, CeF, EuO, GdO, YbO, and YbF. The pseudopotential calculations treat the lanthanoid 4f shell as part of the core and yield accurate estimates for average bond lengths, vibrational frequencies and dissociation energies of all states belonging to a superconfiguration. Information for each individual state of the considered superconfiguration may be obtained from subsequent ligand field model calculations. The results of this combined pseudo-potential and ligand field approach (PPLFT) are compared to more accurate calculations with ab initio pseudopotentials that include the lanthanoid 4f orbitals explicitly in the valence shell and to available experimental data.     

Synthesis and characterisation of a chiral lanthanoid cluster with an unusually exposed cubane core via concomitant deesterification of ethyl acetate

An unusual chiral lanthanoid cluster has been synthesised and characterised that exhibits a cubane cage motif with a remarkably exposed central core. This discovery stems from the use of a new asymmetric diketone ligand, (Z)-3-hydroxy-3-methyl-1-(1,2:3,4-di-O-isopropylidene-α-d-galactopyranose)prop-2-en-1-one (Hmgp), which incorporates both a methyl terminus and a protected d-galactose moiety to induce chirality. Reaction of this ligand with hydrated holmium chloride results in the formation of a cubane cluster, [Ho₄(μ₃-OH)₄(η²-mgp)₆(μ-η²-mgp)(μ-η²-Ac)(H₂O)₂] (1), which bears seven chiral ligands that form a highly shielded hemisphere and an acetate co-ligand that is postulated to form via deesterification of ethyl acetate.     

Copper(II) and lanthanoid(III) complexes of a new β-diketonate ligand with an appended non-coordinating phenol group

New mononuclear compounds of the ligand 1-(2-hydroxyphenyl)-3-phenylpropane-1,3-dione (H₂L) with Cu(II) and several lanthanoid(III) ions, where Ln(III) = Pr, Nd, Eu, Gd, have been synthesized and characterized by spectroscopic methods and X-ray crystal structure determinations. In all compounds, the ligand coordinates in a bidentate chelating manner, using the diketone function. In the [Cu(HL)₂], the coordination geometry of Cu(II) ion is slightly distorted square-planar; two strong intramolecular (OH?O) hydrogen-bonding interactions are established between the phenolate group and the neighboring ketone function. The lanthanoid(III) compounds have the general formula [Ln(HL)₃(CH₃OH)₂] · CH₃OH · 2H₂O; the lanthanoid(III) ion (Ln) is eight-coordinated and the coordination geometry is based on a distorted square-antiprism. In addition to the intramolecular hydrogen bonding (OH?O), intermolecular hydrogen-bonding interactions are also present between the coordinated methanol molecule and the non-coordinated methanol molecule giving rise to a three-dimensional network.     

Complexation thermodynamics of water-soluble calix[4]arene derivatives with lanthanoid(III) nitrates in acidic aqueous solution

Microcalorimetric titrations have been performed in acidic aqueous solution at 25 °C to calculate the complex stability constants (K_S) and thermodynamic parameters (ΔG°, ΔH°, and TΔS°) for the stoichiometric 1:1 complexation of lanthanoid(III) nitrates (La-Gd, Tb) with 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis(hydroxycarbonylmethoxy)calix[4]arene (2) and 5,11,17,23-tetrasulfonato-thiacalix[4]arene (3). Using the present and previous reported data on water-soluble calix[4]arenesulfonates (1) and structurally related analogues 2 and 3, the complexation behavior is discussed comparatively from the thermodynamic point of view. Possessing four carboxyls at the lower rim of parent calix[4]arenesulfonate (1), the derivative 2 displays the enhanced binding abilities for Sm³⁺. As compared with 1 and 2, p-sulfonatothiacalix[4]arene (3) gives not only the lower binding constants for all of lanthanoid(III) ions but also lower cations selectivity. Thermodynamically, the resulting complexes of lanthanoid(III) ions with 1 and its derivatives 2 and 3 is absolutely entropy-driven in aqueous solution, typically showing larger positive entropy changes. These larger positive entropy changes (TΔS°) and somewhat smaller positive enthalpy changes (ΔH°) are directly contributed to the complexes stability as a compensative consequence.     

Extraction Mechanism of Metal Ion from Aqueous Solution to the Hydrophobic Ionic Liquid, 1-Butyl-3-methylimidazolium Nonafluorobutanesulfonate

Summary. We studied the extraction behavior of metal ionic species in aqueous solutions into the hydrophobic ionic liquid, 1-butyl-3-methylimidazolium nonafluorobutanesulfonate ([bmi][NfO]). The extraction ratios (E/%) of Li(I), Na(I), Cs(I), Ca(II), Sr(II), and La(III) species were found to be 39, 24, 5.0, 81, 79, and 98. This result is similar to the phenomena that the metal ions with larger charge are more easily adsorbed onto cation exchange resins. In order to examine the extraction mechanism, we studied the extraction behavior of La(III) species from the aqueous to the [bmi][NfO] phase. As a result, it was found that the E values of La(III) decrease remarkably with an increase in concentrations of HNO₃ (0–1 M) in the aqueous phase and that the amount of La(III) transferred into [bmi][NfO] phase increases linearly with an increase in the amount of [bmi] transferred into the aqueous phase. Furthermore, we investigated the extraction behavior of La(III) species using 1-pentyl- and 1-hexyl-3-methylimidazolium nonafluorobutansulfonate ([pmi][NfO], [hmi][NfO]), which are more hydrophobic than [bmi][NfO], and found out that the E values of La(III) decrease in order of [bmi][NfO] > [pmi][NfO] > [hmi][NfO]. From these results, it was proposed that the extraction of metal ionic species from the aqueous to the [bmi][NfO], [pmi][NfO], or [hmi][NfO] phase is mainly ascribed to the cation exchanges between two phases.     

A study of the formation and application of new chiral water soluble lanthanoid benzoates using real-time infrared spectroscopy

A range of water soluble lanthanoid benzoate complexes of composition [Ln(Bz)₃(H₂O)_n] (Ln = La, Gd, Ho and Yb; Bz = 3,5-bis((R)-2,3-dihydroxypropoxy)benzoate and 3,4,5-tris((R)-2,3-dihydroxypropoxy)benzoate) have been prepared by reaction of lanthanoid bicarbonates with three equivalents of the corresponding optically active benzoic acid in water. Application of [Ln(Bz)₃(H₂O)_n] as asymmetric catalysts for epoxide ring opening reactions has been investigated using styrene oxide, showing complete conversion after 20 h, albeit with no significant enantiomeric excess observed. The formation of the lanthanoid complexes and subsequent catalytic conversion of styrene oxide to phenylethane-1,2-diol were monitored using real-time infrared (RTIR) spectroscopy, yielding information about reaction pathways and intermediates.     

Preparation and crystal structure of the Isotypic Carbides Ln4Ni2C5 (Ln = Er,Tm, Yb and Lu)

The title compounds were prepared from the elemental components in a lithium flux. Their crystal structure was determined for the ytterbium compound from single-crystal X-ray data. It is orthorhombic, Pmm2, a = 352.88(6) pm, b = 1 143.0(3) pm, c = 366.16(6) pm, Z = 1, R = 0.020 for 1 261 structure factors and 29 variable parameters. The structure may be viewed as an intergrowth of slabs consisting of the CeNiC₂ and the ScC (NaCl type) structures. It thus contains C₂ pairs with a C? C distance of 138(1) pm and isolated carbon atoms. Together with the nickel atoms the C₂ pairs form one-dimensionally infinite building elements [Ni₂C₄]_n. The fifth carbon atom is octahedrally coordinated by ytterbium atoms. Accordingly the compound may be rationalized to a first approximation with the formula (Yb³⁺)₄[Ni₂C₄^8?]C^4?. Yb₄Ni₂C₅ shows Curie-Weiss behaviour with a magnetic moment of μ_exp = 4.44 μ_B per ytterbium atom in good agreement with the theoretical moment of μ_eff = 4.53 μ_B for Yb³⁺.     

The Crystal Structure of YPdSi,the Isotypic Compounds LnPdSi (Ln = Gd–Lu), and their Structural Relation to some other Equiatomic Compounds of the Rare Earth and Transition Metals with Main Group Elements

The nine title compounds were prepared from the elements by arc-melting and subsequent heat treatment in resistance and high-frequency furnaces. The crystal structure of these isotypic compounds was determined for YPdSi from single-crystal X-ray diffractometer data: Pmmn, a = 430.8(1) pm, b = 1391.2(1) pm, c = 743.1(1) pm, Z = 8, R = 0.024 for 417 structure factors and 40 variable parameters. The crystal structures of the isotypic compounds GdPdSi and ErPdSi were also refined from single-crystal data. The structure is of a new type. It consists of condensed, six-membered rings of alternating palladium and silicon atoms with Pd–Si bond distances varying between 249.6 and 258.8 pm. These two-dimensionally infinite nets are connected to each other via weak Pd–Si and Si–Si bonds with bond distances of 276.3 and 259.5 pm. The rare earth atoms are situated above and below the six-membered palladium-silicon rings in a manner as it is known for the aluminum atoms in the AlB₂ type structure. The crystal-chemical similarities and topologies of several structures derived from the aristotype AlB₂ (including those of BaPtSb, EuAuGe, KHg₂, ZrBeSi, and TiNiSi) are described, emphasizing their group-subgroup relationships. The previously reported compound ”︁Er₂Pd₂Si”︁”︁ has the same structure as has been found here for ErPdSi.