Synthesis of lanthanide pyrazolonate complexes by the reactions of 1-Phenyl-3-methyl-4-(2,2-dimethylpropan-1-oyl)pyrazol-5-one with metallic lanthanides. Crystal structures of [Ln(Bu t -PMP)3]2 (Ln = Gd, Tb, and Tm)

Lanthanide pyrazolonate complexes Ln(Bu ^t -PMP)₃ (Ln = Pr, Nd, Gd, Tb, Tm, and Lu) are synthesized by the reactions of 1-phenyl-3-methyl-4-(2,2-dimethylpropan-1-oyl)pyrazol-5-one (Bu ^t -PMPH) with metallic lanthanides in the presence of catalytic amounts of the corresponding metal triiodides. The yields of the products are close to quantitative ones. The synthesized compounds can sublime in vacuo (10^?3 Torr) in the temperature range from 235 to 270°C. X-ray diffraction analyses of the sublimed complexes show that they are dimers [Ln(Bu ^t -PMP)₃]₂ (Ln = Gd, Tb, and Tm) in which metal atoms are linked by two bridging pyrazolonate fragments. The coordination environment of the lanthanide is a distorted one-capped trigonal prism.     

Reduction of LnIII to LnII in reactions of LnCl3·6H2O (Ln = Eu,Yb, and Sm) with Bui 2AlH in THF. The formation of soluble luminescent complexes LnCl2·xTHF

Soluble luminescent complexes of divalent lanthanides, LnCl₂·xTHF (Ln = Eu, Yb, and Sm), were obtained for the first time by reduction of Ln^III to Ln^II in reactions of the lanthanide trichloride hexahydrates LnCl₃·6H₂O with Buⁱ ₂AlH in THF. The photoluminescence spectra and other spectral characteristics of LnCl₂·xTHF were examined.     

Synthesis and properties of homoleptic 2,2′-bipyridyl complexes of rare-earth elements. Crystal and molecular structures of the complexes Ln(N2C10H8)4 (Ln=Sm, Eu, Yb, or Lu) and the ionic complex [Lu(N2C10H8)4][Li(THF)4]

Homoleptic 2,2′-bipyridyl complexes of lanthanides (Ln), Ln(bpy)₄, were prepared by the reactions of iodides LnI₂(THF)₂ (Ln=Sm, Eu, Tm, or Yb), LnI₃(THF)₃ (Ln=La, Ce, Pr, Nd, Gd, or Tb), or bis(trimethylsilyl)amides Ln[N(SiMe₃)₂]₃ (Ln=Dy, Ho, Er, or Lu) with bipyridyllithium in tetrahydrofuran (THF) or 1,2-dimethoxyethane in the presence of free 2,2′-bipyridine. The IR and ESR spectral data, the magnetic susceptibilities, and the results of X-ray diffraction analysis indicate that the complexes of all elements of the lanthanide series, except for the europium complex, contain Ln⁺³ cations and anionic bpy ligands. According to the X-ray diffraction data, the coordination polyhedra about the Sm and Eu atoms are cubes, whereas the environment about the Yb atom is a distorted dodecahedron. In the ionic complex [Lu(bpy)₄][Li(THF)₄], the geometry of the [Lu(bpy)₄]⁻ anion is similar to that of the Lu(bpy)₄ complex. The possible modes of charge distributions over the ligands,viz., Ln(bpy²⁻)(bpy^.−)(bpy⁰)₂ and Ln(bpy^.−)₃(bpy⁰), are discussed. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1897–1904, November, 2000.     

Potentiometric determination of novel complexes of selected lanthanide ions with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N’</Emphasis>-bis(5-methylsalicylidene)-4-methyl-1,3-phenylenediamine

The stability constants of the complexes formed in the N,N’-bis(5-methylsalicylidene)-4-methyl-1,3-phenylenediamine (H₂L) and La(III), Eu(III), Gd(III), Ho(III), and Lu(III) ion systems were determined in solution with the potentiometric method. The pH-metric titrations were performed in dimethyl sulfoxide/water (v:v, 30:70) mixture at 25.0 °C in 0.1 M LiNO₃ ionic strength. The tests were performed for systems with Ln(III) to H₂L 1:2 and 1:3 molar ratio but only data of the systems with the metal/ligand ratio 1:2 were taken into calculation. The molar ratio 1:1 was not studied because of the high coordination numbers of the lanthanide ions, and inadequate donor atoms of the ligand. Computer analysis (HYPERQUAD software) of potentiometric data indicated that in solution the lanthanide (Ln) complexes exist as LnL₂, Ln(HL)₂, and Ln(H₂L)₂ forms, depending on pH unlike to the solid state where only one form of Ln(H₂L)₂ occurs. Formation constants increase with decreasing size of the Ln(III) ions. Moreover, complex formation in the Ln³⁺/H₂L systems in solution was performed using UV–Vis spectrophotometric titration.     

Structural, thermal, and spectral investigations of the lanthanide(III) biphenyl-4,4′-dicarboxylates

The lanthanide biphenyl-4,4′-dicarboxylates (bpdc) series of the general formulae Ln₂(bpdc)₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III); bpdc = C₁₂H₅(COO) ₂ ^2? ; n = 4, 5 or 6 have been obtained by the conventional precipitation method. All prepared complexes were characterized by elemental analysis, simultaneous thermal analyses thermogravimetric-differential scanning calorimetry (TG–DSC) and TG–FT-IR, FT-IR, and FT-Raman spectroscopy as well as X-ray diffraction patterns measurements. In the whole series of analyzed complexes the bpdc^2? ligand is completely deprotonated. In view of that, four carboxylate oxygen atoms are engaged in the coordination of Ln(III) ions. The synthesized compounds are polycrystalline and insoluble in water. They crystallize in the low symmetry crystal systems, like monoclinic and triclinic. Heating in the air atmosphere resulted in the multi-steps decomposition process, namely endothermic dehydration and strong exothermic decomposition processes. The dehydration process leads to the formation of stable anhydrous Ln₂bpdc₃ compounds which subsequently decompose to the corresponding lanthanide oxides.     

Mechanism for Solvent Extraction of Lanthanides from Chloride Media by Basic Extractants

The solvent extraction of lanthanides from chloride media to an organic phase containing an anion exchanger in the chloride form is known to show low extraction percentages and small separation factors. The coordination chemistry of the lanthanides in combination with this kind of extractant is poorly understood. Previous work has mainly used solvent extraction based techniques (slope analysis, fittings of the extraction curves) to derive the extraction mechanism of lanthanides from chloride media. In this paper, EXAFS spectra, luminescence lifetimes, excitation and emission spectra, and organic phase loadings of lanthanides in dry, water-saturated and diluted Aliquat 336 chloride or Cyphos IL 101 have been measured. The data show the formation of the hydrated lanthanide ion [Ln(H₂O)_8–9]³⁺ in undiluted and diluted Aliquat 336 and the complex [LnCl₆]^3? in dry Aliquat 336. The presence of the same species [Ln(H₂O)_8–9]³⁺ in the aqueous and in the organic phase explains the small separation factors and the poor selectivities for the separation of mixtures of lanthanides. Changes in separation factors with increasing chloride concentrations can be explained by changes in stability of the lanthanide chloro complexes in the aqueous phase, in combination with the extraction of the hydrated lanthanide ion to the organic phase. Finally, it is shown that the organic phase can be loaded with 107 g·L^?1 of Nd(III) under the optimal conditions.     

N‐Heterocyclic Tridentate Aromatic Ligands Bound to [Ln(hexafluoroacetylacetonate)3] Units: Thermodynamic,Structural, and Luminescent Properties

Herein, we discuss how, why, and when cascade complexation reactions produce stable, mononuclear, luminescent ternary complexes, by considering the binding of hexafluoroacetylacetonate anions (hfac^?) and neutral, semi‐rigid, tridentate 2,6‐bis(benzimidazol‐2‐yl)pyridine ligands ( Lk ) to trivalent lanthanide atoms (Ln^III). The solid‐state structures of [Ln( Lk )(hfac)₃] (Ln=La, Eu, Lu) showed that [Ln(hfac)₃] behaved as a neutral six‐coordinate lanthanide carrier with remarkable properties: 1) the strong cohesion between the trivalent cation and the didentate hfac anions prevented salt dissociation; 2) the electron‐withdrawing trifluoromethyl substituents limited charge‐neutralization and favored cascade complexation with Lk ; 3) nine‐coordination was preserved for [Ln( Lk )(hfac)₃] for the complete lanthanide series, whilst a counterintuitive trend showed that the complexes formed with the smaller lanthanide elements were destabilized. Thermodynamic and NMR spectroscopic studies in solution confirmed that these characteristics were retained for solvated molecules, but the operation of concerted anion/ligand transfers with the larger cations induced subtle structural variations. Combined with the strong red photoluminescence of [Eu( Lk )(hfac)₃], the ternary system Ln^III/hfac^?/ Lk is a promising candidate for the planned metal‐loading of preformed multi‐tridentate polymers.     

Hydrothermal synthesis, thermal and luminescent investigations of lanthanide(III) coordination polymers based on the 4,4′-oxybis(benzoate) ligand

In this study, new series of lanthanide 4,4??-oxybis(benzoates) of the general formula Ln₂oba₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III), oba?=?C₁₂H₈O(COO) ₂ ^2? and n?=?3?C6, has been prepared under hydrothermal conditions. The compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction patterns measurements and different methods of thermal analysis (TG, DSC, and TG-FTIR). In addition, photoluminescence properties of the selected complexes have been investigated. Crystalline compounds are isostructural in the whole series. Both carboxylate groups are deprotonated and engaged in the coordination of Ln(III) ions. Heating of the complexes leads to the dehydration and next decomposition processes. Although of the same structure, the removal of water molecules proceeds in different ways. In the nitrogen atmosphere, they decompose releasing water, carbon oxides and phenol molecules. The complexes of Eu(III), Tb(III) and Dy(III) exhibit photoluminescence in the visible range, whereas the compounds of Nd(III) and Yb(III) in the near-infrared region upon excitation by UV light.     

Noncovalent Tagging Proteins with Paramagnetic Lanthanide Complexes for Protein Study

The site‐specific labeling of proteins with paramagnetic lanthanides offers unique opportunities for NMR spectroscopic analysis in structural biology. Herein, we report an interesting way of obtaining paramagnetic structural restraints by employing noncovalent interaction between a lanthanide metal complex, [Ln(L)₃]^n? (L=derivative of dipicolinic acid, DPA), and a protein. These complexes formed by lanthanides and DPA derivatives, which have different substitution patterns on the DPA derivatives, produce diverse thermodynamic and paramagnetic properties when interacting with proteins. The binding affinity of [Ln(L)₃]^n? with proteins, as well as the determined paramagnetic tensor, are tunable by changing the substituents on the ligands. These noncovalent interactions between [Ln(L)₃]^n? and proteins offer great opportunities in the tagging of proteins with paramagnetic lanthanides. We expect that this method will be useful for obtaining multiple angles and distance restraints of proteins in structural biology.     

Highly Selective Recovery of Lanthanides by Using a Layered Vanadate with Acid and Radiation Resistance

It is of vital importance to capture lanthanides (nuclear fission products) from waste solutions for radionuclide remediation owing to their hazards. The effective separation of lanthanides are achieved by an acid/base‐stable and radiation‐resistant vanadate, namely, [Me₂NH₂]V₃O₇ ( 1 ). It exhibits high adsorption capacities for lanthanides (q_m^Eu=161.4 mg g^?1; q_m^Sm=139.2 mg g^?1). And high adsorption capacities are maintained over a pH range of 2.0–6.9 (q_m^Eu=75.1 mg g^?1 at low pH of 2.5). It displays high selectivity for Eu³⁺ (simulant of An³⁺) against a large excess of interfering ions. It can efficiently separate Eu³⁺ and Cs⁺ (or Sr²⁺) with the highest separation factor SF_Eu/Cs of 156 (SF_Eu/Sr of 134) to date. The adsorption mechanism is revealed by calculations and XPS, EXAFS, Raman, and elemental analyses. These merits combined with facile synthesis and convenient elution makes the title vanadate a promising lanthanide scavenger for environmental remediation.     

Lanthanide(III) Nitrate Complexes of Two 17 Membered N3O2-Donor Macrocycles

The interaction of lanthanide(III) ions with two N₃O₃-macrocycles, L¹ and L², derived from 2,6-bis(2-formylphenoxymethyl)pyridine and 1,2-diaminoethane has been investigated. Schiff-base macrocyclic lanthanide(III) complexes LnL¹(NO₃)₃ · xH₂O (Ln = Nd, Sm, Eu or Lu) have been prepared by direct reaction of L¹ and the appropriate hydrated lanthanide nitrate. The direct reaction between the diamine macrocycle L² and the hydrated lanthanide(III) nitrates yields complexes LnL²(NO₃)₃· H₂O only for Ln = Dy or Lu. The reduction of the Schiff-base macrocycle decreases the complexation capacity of the ligand towards the Ln(III) ions. The complexes have been characterised by elemental analysis, molar conductivity data, FAB mass spectrometry, IR and, in the case of the lutetium complexes, ¹H NMR spectroscopy.     

Comparison of thermal properties of lanthanide trimellitates prepared by different methods

By diffusion in gel medium new complexes of formulae: Nd(btc)⋅6H₂O, Gd(btc)⋅4.5H₂O and Er(btc)·5H2O (where btc=(C₆H₃(COO)₃ ³⁻) were obtained. Isomorphous compounds were crystallized in the form of globules. During heating in air atmosphere they lose stepwise water molecules and then anhydrous complexes decompose to oxides. Hydrothermally synthesized polycrystalline lanthanide trimellitates form two groups of isomorphous compounds. The light lanthanides form very stable compounds of the formula Ln(btc)⋅nH₂O (where Ln=Ce−Gd and n=0 for Ce; n=1 for Gd; n=1.5 for La, Pr, Nd; n=2 for Eu, Sm). They dehydrate above 250°C and then immediately decomposition process occurs. Heavy lanthanides form complexes of formula Ln(btc)⋅nH₂O (_Ln=Dy−Lu). For mostly complexes, dehydration occurs in one step forming stable in wide range temperature compounds. As the final products of thermal decomposition lanthanide oxides are formed.     

Formation Thermodynamics of Binary and Ternary Lanthanide(III) Complexes with 1,10-Phenanthroline and Chloride in N,N-Dimethylformamide

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm^–3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)³⁺ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)³⁺ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)³⁺ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln³⁺-Cl^–-phen system, the formation of LnCl(phen)²⁺, LnCl₂(phen)⁺, and LnCl₃(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.     

Crystal Chemistry of the Saccharinato Complexes of Trivalent Lanthanides and Yttrium

Saccharinate complexes of the fourteen trivalent lanthanide cations and Y^III were prepared by reaction between the respective lanthanide carbonates and saccharin in aqueous solution. Their crystal structures were determined by single crystal X‐ray diffractometry. They represent three different structural types. The first family, of composition [Ln(sac)(H₂O)₈](sac)₂�H₂O (sac = anion of saccharin; Ln = La, Ce, Pr, Nd.Sm, Eu), belongs to the monoclinic space group P2₁/c with Z = 4 and the Ln^III cation is in a tricapped trigonal prismatic environment with nine‐fold oxygen coordination. The second group of composition [Ln(sac)₂(H₂O)₆]‐(sac)(Hsac)�4H₂O with Ln = Gd, Dy, Ho, Er, Yb, Lu, and Y, pertains to the triclinic P1¯‐ space group, with Z = 2 and constitutes a new example of complexes containing simultaneously saccharin and its anion in the lattice. The Tm^III and Tb^III compounds, which are also triclinic (space group P1¯‐ and Z = 2) present two closely related structures conformed by three and two [Ln(sac)(H₂O)₇]²⁺ crystallographically independent complexes, respectively, with the [Tm(sac)(H₂O)₇]₃(sac)₆�9H₂O and [Tb(sac)(H₂O)₇]2(sac)₄�6H₂O composition. For all the heavier lanthanides (Gd‐Lu) and yttrium the cation presents eight‐fold oxygen coordination, with the ligands at the corners of a slightly distorted square Archimedean antiprism.     

Adsorption of lanthanides on mordenite from nitrate medium

The adsorption of lanthanides (except for Pm) on mordenite was investigated under various solution conditions of nitrate ion concentrations ([NO*3]: 0.001-2 mol/dm3) and total lanthanide concentrations (0.0005 mol/dm3). Solutions of lanthanide nitrates were equilibrated with zeolite samples at 296 K. A concave tetrad effect was evident in the change of logK d values within the lanthanide series and an explanation by a comparison of covalence in Ln-O bonds existing in triple bond Al-O(1/3Ln)-Si species found in the zeolite phase and in Ln(H2O)3+x or Ln(NO3) n-3 n complexes formed in the aqueous phase is presented. The decreasing trend in C1 and C3 coefficients, which are the function of E1 and E3 Racah f-interelectron repulsion parameters, is evidence of the magnification of covalence in Ln-O bond in the series triple bond S-iO(1/3Ln)-Al triple bond 相似文献   

Potentiometric Study of Lanthanide Salicylaldimine Schiff Base Complexes

Formation of complexes between the lanthanide ions and N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand was studied in solution by pH potentiometry. The potentiometric titration was performed at 25.00 °C in 0.1 mol·dm^?3 NaClO₄ ionic strength and in DMSO:water (30:70 v:v) solvent mixture. N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand (H₂L) occurs in three forms: fully or partially deprotonated and unionized. Computer analysis of potentiometric data indicated that in solution the lanthanide (Ln) complexes exist as LnL₂, Ln(HL)₂ and Ln(H₂L)₂ species. This observation appears to be in contrast to the solid-state behavior of these complexes prepared in a self-assembly process and structurally defined. Stability constants for La³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Ho³⁺ and Lu³⁺ (Ln³⁺) complexes were determined. The order of stabilities of LnL₂ species in terms of metal ions is La³⁺ > Eu³⁺ ≈ Gd³⁺ = Tb³⁺ < Ho³⁺ < Lu³⁺ with a prominent “gadolinium break”.     

Structural study of lanthanides(III) in aqueous nitrate and chloride solutions by EXAFS

Structural studies of lanthanide ions (Nd³⁺≈Lu³⁺: about 1 mol/l) in the aqueous chloride (HCl: 0≈6 mol/l) and nitrate (HNO₃: 0?13 mol/l) solutions were carried out by extended X-ray absorption fine structure (EXAFS). The radial structural functions appeared to be mainly characterized by hydration in both chloride and nitrate systems and coordination of nitrate ion in nitrate systems. These results indicated that nitrate ion forms inner-sphere complex with lanthanide but chloride ion hardly forms one. The quantitative analyses of EXAFS data have revealed that the total coordination numbers of lanthanide ranged from about 9 for light lanthanides to about 8 for heavy lanthanides in all the samples. The bond distances of Ln?O were from about 2.3 to 2.5 Å for Ln?OH₂ and from about 2.4 to 2.6 Å for Ln?O₂NO. Nitrate ion locates at 0.1 Å longer position than water, it suggested that nitrate ion ligates more weakly than water.     

Formation of heterometallic compounds in mixed solutions of nickel(II)-Schiff base complexes and lanthanide nitrates: Electrospray ionization mass spectrometry data

Atmospheric-pressure electrospray ionization mass spectrometric data are reported for methanolic Ni(SB) + Ln(NO₃)₃ · nH₂O solutions (H₂SB = N,N′-ethylene-bis(salicylaldiimine), N,N′-ethylene-bis(3-methoxysalicylaldiimine), N,N′-ethylene-bis(acetylacetonediimine); Ln = La, Eu, Lu). Dinuclear and trinuclear heterometallic complexes of composition [(Ni(SB)) _x Ln(NO₃)₃] (x = 1, 2) form in these solutions. The dinuclear-totrinuclear ion intensity ratio depends on the natures of the lanthanide and the Schiff base.     

Coordination and recognition of lanthanide cations by a methyl-substituted cucurbit[6]uril derived from 3α-methyl-glycoluril

The interactions between a series of lanthanide cations (Ln³⁺) and a methyl-substituted cucurbit[6]uril derived from 3α-methyl-glycoluril (SHMeQ[6]) in the presence of [CdCl₄]^2 ? as a structure-directing agent in aqueous HCl solutions (6.0 mol·L ^? 1) have been investigated. The formation of ionic radius-dependent complexes, the crystal structures of six of which have been obtained, shows the recognition ability of SHMeQ[6] towards lanthanide cations. For example, SHMeQ[6] forms molecular capsule-like complexes with the two lightest lanthanide cations, La³⁺ and Ce³⁺; molecular pairs with Nd³⁺, Sm³⁺, Eu³⁺ and Gd³⁺, and no solid crystals are formed with the heavier lanthanides.     

Synthesis,Structures, and Luminescent Properties of Chloride and Nitrate LnIII Complexes Coordinated by tris(Pyrazolyl)methane

We report the synthesis of Ln³⁺ nitrate [Ln(Tpm)(NO₃)₃] ⋅ MeCN (Ln=Yb ( 1Yb ), Eu ( 1Eu )) and chloride [Yb(Tpm)Cl₃] ⋅ 2MeCN ( 2Yb ), [Eu(Tpm)Cl₂(μ-Cl)]₂ ( 2Eu ) complexes coordinated by neutral tripodal tris(3,5-dimethylpyrazolyl)methane (Tpm). The crystal structures of 1Ln and 2Ln were established by single crystal X-ray diffraction, while for 1Yb high resolution experiment was performed. Nitrate complexes 1Ln are isomorphous and both adopt mononuclear structure. Chloride 2Yb is monomeric, while Eu³⁺ analogue 2Eu adopts a binuclear structure due to two μ²-bridging chloride ligands. The typical lanthanide luminescence was observed for europium complexes ( 1Eu and 2Eu ) as well as for terbium and dysprosium analogues ([Ln(Tpm)(NO₃)₃] ⋅ MeCN, Ln=Tb ( 1Tb ), Dy ( 1Dy ); [Ln(Tpm)Cl₃] ⋅ 2MeCN, Ln=Tb ( 2Tb ), Dy ( 2Dy )).