Gd Lu Research Articles

Contrasting exchange interactions in the new R3Pd5 (R = Tb, Dy, Ho, Er) compounds. Multiple magnetic transitions, spin-reorientation and frustration, as revealed by temperature dependent neutron diffraction studies: A question of sublattices?

In a recent work we have reported the formation and the crystal structure of the new family of compounds R3Pd5 (R = Sc, Y, Gd–Lu; Pu3Pd5-type, oS32, spacegroup 63, Cmcm). DFT calculations for Gd3Pd5 and heat capacity and magnetic measurements for Tb3Pd5, Dy3Pd5, Ho3Pd5 and Er3Pd5 were able to discriminate at least two distinct antiferromagnetic transitions at low temperatures; at the same time these data suggested these separate magnetic orderings to be likely associated to the two structurally different rare earth sublattices (4c and 8e, respectively). The magnetic structures of the R3Pd5 compounds, with R = Tb, Dy, Ho, Er, have been now investigated in this work. High-resolution and high-intensity neutron powder diffraction data were recorded for the four compounds of the series. The results reveal that the magnetic structures adopted are significantly diverse and their temperature dependence more complex than originally deduced from magnetic and heat capacity measurements. Tb3Pd5 is in fact the only of the four compounds where the rare earth sublattices order independently with two different magnetic propagation vectors on the two sites (k1 = [1 0 ½] for Tb2 and k2 = [kx 0 0] or k3 = [1 0 0] for Tb1). In Dy3Pd5 both sublattices follow the propagation vector k = [kx 0 0], with the second transition corresponding to a spin reorientation. In Ho3Pd5 ordering of both sublattices follow the k = [1 0 0] propagation vector; the second transition seen in the magnetic and heat capacity data corresponds to an accelerated increase in the magnetic moment of the Ho2 sublattice. The case of Er3Pd5 is special as it is the sole case where one of the rare earth sublattices does not order down to T = 1.5 K; here the second transition determined from the magnetic data corresponds to a change of the magnetic propagation vector from k1 = [kx 0 kz] to k2 = [1 0 0], both only acting on the Er2 sublattice. Irrespectively of the very similar structures not even two of the four studied R3Pd5 compounds show identical magnetic structures on either of the two sublattices. These strong variations have to be connected to changes in the RKKY interactions induced by the progressive filling of the f-orbitals of the heavy rare earth ions and the concomitant changes of the crystal electric fields.

Structural state of rare earth elements in eudialyte-group minerals

AbstractEudialyte-group minerals (EGM) attract global interest as potential resources for high-field-strength elements (e.g. Zr, Nb, Ta, and rare-earth elements), i.e. critical materials for modern technologies. They are particularly valued for their relative enrichment in the most critical lanthanides, i.e. Nd and heavy rare earth elements (Gd–Lu). However, rare earth element (REE) substitution mechanisms into the EGM structure are still poorly understood. Light and heavyREEmay occupy different sites and there may be ordering and/or defect clustering in the structure. This study uses X-ray absorption spectroscopy to determine the structural state ofREEin EGM from prospective eudialyte-bearing complexes. YttriumK-edge and NdL3-edge spectra were collected as proxies for heavy and lightREE, respectively, and compared to natural and syntheticREE-bearing standards. Extended X-ray absorption fine structure data yield best fits for Y in six-fold coordination with Y–O distances of 2.24–2.32 Å, and a second coordination sphere comprising Fe, Na, Ca, Si and O at radial distances of 3.6–3.8 Å. These findings are consistent with dominant Y3+substitution for Ca2+on the octahedralM1 site in all the samples studied, and exclude preferential substitution of Y3+onto the smaller octahedralZsite or the large low-symmetryN4 site.Using lattice strain theory, we constructed relative partitioning models to predict site preferences of lanthanides we have not measured directly. The models predict that allREEare favoured on the Ca-dominantM1 site and that preferential partitioning of heavy over lightREEincreases in EGM containing significant Mn in theM1-octahedral rings (oneillite subgroup). Thus, the flatREEprofiles that make EGM such attractive exploration targets are not due to preferential partitioning of light and heavyREEonto different sites. Instead, local ordering of Mn- and Ca-occupiedM1 sites may influence the capacity of EGM to accommodate heavyREE.

Synthesis, crystal structure and physical properties of Yb2Pd3Ge5

A systematic study on the existence of R2Pd3Ge5 intermetallics with heavy rare earth metals (R = Gd–Lu) was conducted; only the Yb2Pd3Ge5 was revealed to exist. Its crystal structure was established by X-ray powder diffraction and refined by means of Rietveld method. This compound crystallizes in the orthorhombic U2Co3Si5 structure type (Ibam, oI40, Z = 4, a = 10.2628(1), b = 12.0580(1), and c = 5.98251(6) Å), which represents an ordered derivative of the tI10-ThCr2Si2 prototype, ubiquitous among intermetallics.Magnetization and susceptibility measurements indicate that Yb2Pd3Ge5 is a paramagnet with μeff close to 0.8 μB/Yb-atom, suggesting a nearly divalent Yb state. Electrical resistivity and Seebeck coefficient of the studied compound as a function of temperature confirm its metallic-like behavior.

Structural and magnetic investigations of the pseudo-ternary RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) – size dependent formation of two different structure types

Abstract Several rare earth metal containing pseudo-ternary compounds in the RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) have been synthesized from the elements by arc-melting or in tantalum capsules. Within the Rh series, the compounds with RE=La–Nd crystallize in the cubic MgCu2-type (Fd3̅m) structure. For Sm besides the cubic Laves phase also the hexagonal Laves phase (MgZn2 type, P63/mmc) is found. For the remaining compounds of both series, also the hexagonal MgZn2-type structure is observed. The structures of Ho2Ru0.96(1)Al3.04(1) (a=547.4(1), c=875.7(1) pm, wR=0.0397, 201 F 2 values, 13 variables), Sc2Rh1.01(1)Al2.99(1) (a=528.0(1), c=852.8(1) pm, wR=0.0228, 184 F 2 values, 13 variables), Ho2Rh1.00(1)Al3.00(1) (a=546.5(1), c=873.8(1) pm, wR=0.0590, 222 F 2 values, 13 variables) and Tb2Ir1.06(1)Al2.94(1) (a=550.8(1), c=870.0(1) pm, wR=0.0743, 221 F 2 values, 13 variables) have been refined from single-crystal data, indicating T/Al mixing on both crystallographic Zn sites of the aristotype. The Sc, Y, La and Lu containing compounds exhibit Pauli-paramagnetic behavior, while the other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Ferro- and antiferromagnetic ordering up to T C=50.2(1) K for Gd2RhAl3 is observed, while Sm2RuAl3 shows van Vleck paramagnetism and Yb2RuAl3, finally, exhibits only partially trivalent Yb atoms, evident from a reduced magnetic moment and increased lattice parameters.

Predicting the Phase Stability of Sc1–xLn x PO4 (Ln = Gd–Lu, Y) Zircon-Structured Solid Solutions

The energies of mixing (interaction parameters) in the Sc1–xLn x PO4 (Ln = Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) systems have been calculated using Urusov’s crystal energy theory of isomorphous substitutions. The decomposition (stability) temperatures of the solid solutions have been plotted against the atomic number of the rare-earth elements at x = 0.01, 0.03, 0.05, 0.10, 0.20, and 0.50. The present results can be helpful in a search for host and activator compositions for new luminescence, laser, and other materials based on the zircon-structured rare-earth orthophosphates.

A New Look at the Occurrences of the Rare-Earth Elements in the Georgia Kaolins

AbstractThe high-density siliciclastic minerals (e.g. zircon) in the coarse fractions (>44 mm, informally known as grit) of the mined Georgia kaolins are potential and significant sources of the rare-earth elements (REE). The abundances and provenance of the REE signature have not been studied extensively for the Georgia kaolins. The objective of the present study was, therefore, to define the contribution of these heavy minerals (e.g. zircon) to the REE inventory of the coarse fractions of Georgia kaolins. Heavy-mineral subfractions separated from the coarse fractions contained 1647 mg/kg REE from the Jeffersonville Member of the Lower Tertiary Huber Formation and 5012 mg/kg REE from the Buffalo Creek Kaolin Member of the Upper Cretaceous Galliard Formation, respectively. These heavy-mineral subfractions were enriched 10–100 times in the heavy rare-earth elements (HREE, Gd—Lu,), Hf, and Zr relative to the concentrations of these elements in Upper Continental Crust. The heavy-mineral subfractions comprised 5% of the coarse fractions (grit) of these two kaolin-producing formations. The heavy-mineral subfractions consisted of zircon, anatase, rutile, kaolinite, and minor amounts of muscovite, trace ilmenite, and staurolite. The large concentrations of REE were obtained by separating the dense heavy minerals from the coarse fraction (grit) obtained during the typical production of kaolin-group minerals (kaolinite) from kaolin ore. The amount of zircon (estimated from the 6–11 wt.% Zr) and the absence of monazite did not explain the high concentrations of REE in the heavy-mineral subfractions. The large amounts of REE could have resulted from the sorption of REE released during weathering reactions, or from the presence of small amounts (0.025 wt.%) each of monazite and xenotime in addition to the presence of zircon. This heavymineral subfraction represented a novel domestic resource of extractable REE, especially the HREE, of a grade as high as 0.50 wt.% total REE.

Equiatomic rare earth rhodium plumbides RERhPb (RE=Y, La–Nd, Sm, Gd–Lu) with ZrNiAl-type structure

Abstract The equiatomic plumbides RERhPb (RE=Y, La–Nd, Sm, Gd–Lu) were synthesized by induction melting of the elements in sealed niobium ampoules. The samples were characterized by X-ray powder diffraction, confirming their ZrNiAl-type structure, space group P6̅2m. Four structures were refined from single-crystal X-ray diffractometer data: a=769.42(5), c=415.60(3) pm, wR=0.0415, 343 F 2 values, 15 variables for LaRhPb, a=767.91(6), c=369.37(4) pm, wR=0.0798, 284 F 2 values, 15 variables for ErRhPb, a=767.01(8), c=366.21(4) pm, wR=0.0380, 341 F 2 values, 15 variables for YbRhPb and a=766.9(1), c=363.42(6) pm, wR=0.0699, 290 F 2 values, 15 variables for LuRhPb. The RERhPb plumbides contain two crystallographically independent rhodium atoms, both in tricapped trigonal prismatic coordination: Rh1@Pb3 RE 6 and Rh2@RE 6Pb3. Short Rh–Pb distances (277 and 284 pm in ErRhPb) are indicative of covalent Rh–Pb bonding. The crystal chemical details of the RERhPb series are compared with the silver plumbides REAgPb which show different transition metal-lead coloring. Temperature dependent magnetic susceptibility data show Pauli paramagnetism for YRhPb, LaRhPb and LuRhPb. An antiferromagnetic ground state below the Néel temperatures of 13.5, 21.0 and 6.9 K was found for PrRhPb, TbRhPb and DyRhPb, respectively. HoRhPb exhibits Curie-Weiss behavior in the observed temperature range.

Facile in-situ reduction: Crystal growth and magnetic studies of reduced vanadium (III/IV) silicates CaxLn1−xVSiO5 (Ln = Ce–Nd, Sm–Lu, Y)

A series of lanthanide containing mixed-valent vanadium (III/IV) silicates of the type CaxLn1−xVSiO5 (Ln = Ce–Nd, Sm–Lu, Y) was synthesized as high quality single crystals from a molten chloride eutectic flux, BaCl2/NaCl. Utilizing Ca metal as the reducing agent, an in-situ reduction of V5+ to V3+/4+ as well as of Ce4+ to Ce3+ was achieved. The structures of 14 reported isostructural compounds were determined by single crystal X-ray diffraction. They crystallize in the tilasite (CaMgAsO4F) structure type in the monoclinic space group C2/c. The extended structure contains 1D chains of VO6 octahedra that are connected to each other via SiO4 groups and (Ca/Ln)O7 polyhedra. The magnetic susceptibility and the field dependent magnetization data were measured for CaxLn1−xVSiO5 (Ln = Ce–Nd, Sm, Gd–Lu, Y), and support the existence of antiferromagnetic behavior at low temperatures.

Garnet and scheelite as indicators of multi-stage tungsten mineralization in the Huangshaping deposit, southern Hunan province, China

The Huangshaping W–Mo–Pb–Zn deposit in southern Hunan province, south China, contains multiple generations of garnet and scheelite in skarn and sulfide–carbonate altered rocks. Optical characteristics and chondrite-normalized rare earth element (REEN) patterns obtained by in situ laser ablation–inductively coupled plasma–mass spectrometry analysis were used to distinguish different generations of garnet and scheelite. These data show a clear correspondence of garnet REEN patterns to major element zonation, with HREEs (e.g., Gd–Lu) being depleted overall. Coarse-grained garnets in the Huangshaping deposit have extreme HREE depletions and significant LREE (e.g., La–Eu) enrichment, particularly for Ce, Pr, and Nd. This indicates that REEs in these garnets are the result of coupled substitutions: [Ca2+]VIII− 1[REE3+]VIII+1 and [Fe2+]IV +1[Al3+]IV − 1. Medium-grained garnets have REEN patterns showing significant LREE enrichment and depleted HREEs, with high Sn contents. This suggests that substitution of REEs in these garnets occurs as [Ca2+]VIII−1[REE3+]VIII+1[Sn4+]IV−1[Al3+]IV+1. The fact that medium-grained garnets have high Sn contents indicates mineralizing fluids were oxidizing, which is consistent with significant positive Eu anomalies. However, hump-shaped REEN patterns for garnet rims suggest substitution by: [Ca2+]VIII−2[Na+]VIII+1[REE3+]VIII+1, where Nd–Tb are preferentially incorporated into the garnet lattice over other REEs.Group-1a scheelite has black cores in cathodoluminescence images, and REEN patterns showing extreme LREE enrichment and HREE depletion. Group-1b scheelite has cores with fine oscillatory zoning and enriched LREEs with depleted HREEs, similar to the REEN patterns of Group-2a scheelite that occur as rims with bright CL surrounding both Group-1a and 1b scheelite. The substitution mechanism for REEs in these three types of scheelite is: [Ca2+]VIII−3[ ]VIII+1[REE3+]VIII+2, with [ ] being a Ca site vacancy. The influence of REE speciation in the hydrothermal fluid dominates the REEN patterns of these types of scheelite. However, for Group-2b bright rims of scheelite, REEs are incorporated as: [Ca2+]VIII−2[Na+]VIII+1[REE3+]VIII+1, similar to the garnet rims. Finally, scheelite Mo contents and δEu values that decrease from Group-1a to 2b support a temporal decrease in oxygen fugacity of the mineralizing fluids.Ratios of Y/Ho and Mo contents that decrease from Group-1a and 1b to Group-2a and 2b scheelites are similar to those in porphyry-related skarn W (Mo) and quartz vein Au–W deposits, respectively. Our studies also suggest that all these scheelites in this deposit formed from magmatic fluids. At the Huangshaping deposit, medium-grained garnets associated with Group-1a scheelite precipitated from evolved magmatic fluids during prograde metamorphism, as indicated by their complementary Y/Ho ratios. Paragentically younger scheelite, particularly Group-2b, may have formed from dilute magmatic fluids that underwent large-scale hydrothermal circulation. The characteristics of Group-1b and 2a scheelite likely reflect a transitional environment and fluid mixing during tungsten mineralization in the polymetallic Huangshaping deposit.

R2-xTi3+xGe4 compounds in the R–Ti–Ge (R = Gd–Lu) systems

R2-xTi3+xGe4 compounds in the R–Ti–Ge (R = Gd–Lu) systems

The R10Pd21 compounds (R = Y, Pr, Nd, Sm, Gd–Lu). Crystal structure and magnetism of the ‘RPd2’ phases

The unknown RPd2, for many years expected to be a simple Laves phase, is actually a much more complex compound with stoichiometry R10Pd21.

β-Y(BO2)3 – a new member of the β-Ln(BO2)3 (Ln=Nd, Sm, Gd–Lu) structure family

Abstract β-Y(BO2)3 was synthesized in a Walker-type multianvil module at 5.9 GPa/1000°C. The crystal structure has been elucidated through single-crystal X-ray diffraction. β-Y(BO2)3 crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a =15.886(2), b =7.3860(6), and c =12.2119(9) Å. Its crystal structure will be discussed in the context of the isotypic lanthanide borates β-Ln(BO2)3 (Ln =Nd, Sm, Gd–Lu).

Elastic properties of rare earth pyrochlores R2Ti2O7 (R = Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu): Ab initio calculations

The experimental elastic constants of R2Ti2O7 (R = Gd–Lu), in particular for R = Tb, Dy, Ho published in scientific literature up to now are slightly different, so this makes an ab initio investigation of the current elastic constants for the whole rare-earth row R2Ti2O7 (R = Gd-Lu). The aim of this paper is to give the ab initio calculations of the structural and elastic properties for a whole row of rare-earth titanate pyrochlores in terms of the MO LCAO approximation, using hybrid DFT Hamiltonian PBE0, with periodic code CRYSTAL14. First, the geometry optimization was performed using the analytical energy gradients, with respect to atomic coordinates and unit cell parameters. All-electron Gaussian basis sets were adopted for Titanium and Oxygen and for Rare-Earth atoms internal shells up to 4f are replaced by the pseudopotentials. The results obtained are discussed and the agreement between the calculated values and experimental data are quite satisfactory.

Polymorphism in the family of Ln6−xMoO12−δ(Ln = La, Gd–Lu; x = 0, 0.5) oxygen ion- and proton-conducting materials

Arrhenius plots of the total conductivity in (1 and 3) dry and (2 and 4) wet air of two Yb6MoO12polymorphs: (1 and 2) bixbyite (Ia3̄(206)) Yb6MoO12and (3 and 4) rhombohedral (R3̄) Yb6MoO12; Yb6MoO12rhombohedral (R3̄) → Yb6MoO12bixbyite (Ia3̄(206)) atT∼ 1600 °C.

Trends in thermodynamic parameters of phase transitions of lanthanide sulfides SrLnCuS3 (Ln = La–Lu)

SrLnCuS3 (Ln = La–Lu) compounds melt incongruently. Their thermochemical parameters are determined. The melting temperatures and the enthalpies of melting are: for SrLaCuS3, T = 1513 K and ΔH = 6.9 kJ mol−1; for SrCeCuS3, T = 1468 K and ΔH = 5.2 kJ mol−1; for SrPrCuS3, T = 1459 K and ΔH = 13.2 kJ mol−1; for SrNdCuS3, T = 1429 K and ΔH = 16.8 kJ mol−1; and for SrSmCuS3, T = 1605 K and ΔH = 2.8 kJ mol−1. Three high-temperature polymorphic transitions are found to occur in SrLnCuS3 (Ln = Sm, Gd–Lu) compounds. The parameters of these transitions are determined: for SrSmCuS3, Tα ↔ β = 1452 K, ΔHα ↔ β = 3.0 kJ mol−1, Tβ ↔ γ = 1464 K, ΔHβ ↔ γ = 0.2 kJ mol−1, Tγ ↔ δ = 1476 K, and ΔHγ ↔ δ = 1.1 kJ mol−1; for SrDyCuS3, Tα ↔ β = 1530 К, Tβ ↔ γ = 1568 К, and Tγ ↔ δ = 1585 K; for SrTmCuS3, Tα ↔ β = 1580 K, Tβ ↔ γ = 1618 K, and Tγ ↔ δ = 1631 K; and for SrYbCuS3, Tα ↔ β = 1567 K, Tβ ↔ γ = 1608 K, and Tγ ↔ δ = 1621 K. The transitions are observed both upon heating and upon cooling. The high-temperature phases are not quenchable. Phase-transition temperature versus r(Ln3+) curves for SrLnCuS3 (Ln = La–Lu) feature the tetrad effect. The SrLnCuS3 (Ln = La–Nd) compounds are classified as thiocuprates; their melting temperatures decrease systematically from La to Nd. The SrCuLnS3 (Ln = Sm, Gd–Lu) compounds are classified as thiolanthanates; their melting temperatures increase in the order from Sm to Tm and from Tm to Lu.

New R3Pd5 Compounds (R = Sc, Y, Gd–Lu): Formation and Stability, Crystal Structure, and Antiferromagnetism

The phases reported in the literature as “R2Pd3” (R = rare earth element) have been reinvestigated. The exact stoichiometric composition of this series of compounds, which form for R = Sc, Y, and from Gd to Lu, including Yb, was found to be R3Pd5. All of them crystallize in the orthorhombic Pu3Pd5 structure type (oS32-Cmcm). The crystal structure has been refined from both single crystal (for Tb3Pd5) and powder X-ray diffraction data (for Tb3Pd5, Ho3Pd5, and Tm3Pd5). These compounds represent the first example of a binary phase formed by R and Pd adopting the Pu3Pd5-type featuring two crystallographic nonequivalent sites for the R atoms in the unit cell (the Wyckoff sites 4c and 8e). The variation of the lattice parameters and unit cell volume along the series strictly follows the trend of the lanthanide contraction. An extrapolation of the volume contraction versus the R3+ ionic radius gives an atomic volume of 29.74 A3 for Yb in the hypothetical trivalent metallic state (under normal conditions). The fo...

Homogeneity ranges and physical properties of ternary Laves phases RxZr1-xNi2 (R = Gd–Lu)

Homogeneity ranges and lattice parameters of the ternary compounds RxZr1-xNi2 (R = Gd−Lu) with cubic MgCu2-type structure have been refined from powder XRD and EDXS data: 0.22 ≤ x ≤ 0.27 for Gd, 0.12 ≤ x ≤ 0.27 for Tb and Ho, 0.12 ≤ x ≤ 0.24 for Dy, Er, and Tm, 0.22 ≤ x ≤ 0.24 for Yb and 0.23 ≤ x ≤ 0.24 for Lu at 870 K. The crystal structure has been also investigated for two single crystals Dy0.16Zr0.84Ni2 and Tm0.17Zr0.83Ni2 from the XRD data: MgCu2 type structure, space group Fd3¯ m, Z = 8, a = 6.988(5) Å, R1 = 0.055 for 54 independent reflections Io > 2σ(Io)) for Dy0.16Zr0.84Ni2 and a = 6.976(5) Å, R1 = 0.053 for 46 independent reflections Io > 2σ(Io) for Tm0.17Zr0.83Ni2. The electronic structure of RxZr1-xNi2 was studied with the TB-LMTO method. Y0.22Zr0.78Ni2 and Lu0.23Zr0.77Ni2 are temperature independent Pauli paramagnets and exhibit for T < 6 K a simple normal metal behavior with a Debye temperature ΘD near 370 K RxZr1-xNi2 (R = Dy to Tm) reveal a Curie–Weiss paramagnetic behavior down to 3 K with effective magnetic moments approximately corresponding to the value of R3+ ions.

Sandwich-type lanthanide(III) complexes of a tetraiminodiphenol macrocyclic ligand derived from 4-methyl-2,6-diformylphenol and 1,3-diaminopropane: structure, NMR and luminescence

The macrocyclic ligand salt [H2LH2](ClO4)2, derived from the [2+2] condensation process involving 4-methyl-2,6-diformylphenol and 1,3-diaminopropane, has been used to synthesize the sandwich-type lanthanide(III) complexes [Ln(LH2)2](ClO4)3·2H2O (1–6, Ln=La–Eu, except Pm), [Ln(LH2)2](ClO4)3·CH3CN (7–13, Ln=Gd–Lu, except Er) and [Ln(LH2)(LH)](BPh4)2 (14–16, Ln=La, Nd and Sm). The X-ray crystal structures of the compounds 1, 7, 12, 13, 14 and 15 have been determined. In the isostructural [Ln(LH2)2](ClO4)3·CH3CN complexes of Gd (7), Yb (12) and Lu (13), the two macrocyclic ligands are considerably folded, albeit to different extents, and not symmetrically bound to the metal center. In these compounds, the metal center is coordinated with two imine nitrogen atoms and two phenolate oxygen atoms of each of the ligands (LH2), whose two other uncoordinated imine nitrogens are protonated and intramolecularly hydrogen-bonded with the phenolate oxygens. The structures determined for the La (14) and Nd (15) complexes of [Ln(LH2)(LH)](BPh4)2 are found to be identical. In these complexes, the ligand LH contains one N–H⋯O hydrogen-bonded unit, as against two in the ligand LH2. The [Ln(N2O2)2] coordination polyhedron in all the cases is a distorted square antiprism, although the extent of distortion in 7, 12 and 13 is less compared to that in 14 and 15. 1H NMR spectra of the [Ln(LH2)2]3+complexes in solution indicate a C2 symmetry. The 1H and 13C NMR signals of the EuIII complex 6 have been assigned on the basis of COSY, DEPT, HMQC and NOESY spectra. The photoluminescence spectra of the Sm(III) (5) and Eu(III) (6) complexes have been studied in a methanol–ethanol (1:4) glassy matrix at 77K. The luminescence intensity of the hypersensitive 5D0→7F2 transition in 6 increases with the addition of triethylamine due to the formation of [Eu(LH2)(LH)]2+ and [Eu(LH)2]+ species, which in turn partially attenuate the quenching effect of the N–H⋯O oscillators on the emitting states of the metal ion.

ChemInform Abstract: Rhodium‐Rich Germanides RERh4Ge2 (RE: Y, Gd—Lu): Structure and Bonding.

AbstractThe title compounds are prepared by arc‐melting of the elements and subsequent annealing (evacuated silica tube, 970 K, 5d).

Syntheses and crystal structures of the rare-earth metal(III) bromide ortho-oxidotungstates(VI) with the formula REBr[WO4] (RE = Y, Gd–Yb)

The rare-earth metal(III) bromide ortho-oxidotungstates(VI) with the formula REBr[WO4] crystallize triclinically in space group P1¯ (a = 689–693, b = 715–728, c = 1074–1107 pm, α = 103–106, β ≈ 108 and γ = 93–95°, Z = 4) for RE = Y, Gd–Yb. Their crystal structure is isotypic with the most examples of the formally analogous lanthanoid(III) bromide oxidomolybdates(VI) REBr[MoO4] with RE = Y, Pr, Nd, Sm, Gd–Lu. It contains two crystallographically different rare-earth metal(III) cations with coordination numbers of seven plus one for (RE1)3+ and seven for (RE2)3+. The (RE1)3+ cations are surrounded by three Br– and four plus one O2− anions forming distorted trigonal dodecahedra, while the (RE2)3+ cations exhibit a coordination environment of one Br– and six O2− anions in the shape of a monocapped trigonal prism. Furthermore, the structure contains two crystallographically independent, isolated tetrahedral [WO4]2− units. All these polyhedra are fused together to form 1∞{REBr[WO4]} chains running along [012]. Since the title compounds, synthesized by solid-state reactions from the underlying binaries, emerge as pure phases according to X-ray powder diffractometry, spectroscopic and magnetic measurements were performed.