New complexes of lanthanide Ln(III), (Ln = La, Sm, Gd, Er) with Schiff bases derived from 2-furaldehyde and phenylenediamines

Some new Schiff bases derivates from 2-furaldehyde and phenylenediamines (L^1-3) and their complexes with lanthanum (La), samarium (Sm), gadolinium (Gd) and erbium (Er) have been synthesized. These complexes with general formula [Ln(L^1-3)₂(NO₃)₂]NO₃·nH₂O (Ln = La, Sm, Gd, Er) were characterized by elemental analysis, UV-Vis, FT-IR and fluorescence spectroscopy, molar conductivity and thermal analysis. The metallic ions were found to be eight coordinated. The emission spectra of these complexes indicate the typical luminescence characteristics of the Sm(III), La(III), Er(III) and Gd(III) ions.     

Interactions of trivalent lanthanide cations with a hexadentate Schiff base derived from the condensation of ethylenediamine with 8-hydroxyquinoline-2-carboxaldehyde

Lanthanide(III) complexes [Ln(NO₃)₂(HL)] where Ln?=?La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb and Lu and LH₂?=?N,N′-bis(quinolin-8-ol-2-ylmethylidene)ethane-1,2-diamine, have been obtained by direct reaction of the di-Schiff base ligand and the corresponding hydrated lanthanide(III) nitrates in methanol/DMF solvent systems. All complexes were characterized with microanalyses, spectroscopically (IR and electronic spectra) and thermogravimetrically. Theoretical studies have also been undertaken to estimate possible structures. All the data are discussed in terms of the nature of the bonding and the possible structural types. All complexes appear to be monomeric with the organic ligand being singly deprotonated and behaving as a hexadentate chelating ligand.     

The sorption properties of carbon nanotubes modified with tetraphenylmethylenediphosphine dioxide in nitric acid media

The distribution of microamounts of La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous solutions of HNO₃ and multiwalled carbon nanotubes noncovalently modified with tetraphenylmethylenediphosphine dioxide (L) was considered depending on the concentration of HNO₃ in the aqueous phase and L in the sorbent phase. Ln(III) ions were shown to pass to the sorbent phase in the form of solvated nitrates Ln(NO₃)₃L₃. The effectiveness of the extraction of such complexes decreases along the series of rare-earth metals as the atomic number of the element in the Periodic Table increases.     

2,2′‐Bipyrimidine as Efficient Sensitizer of the Solid‐State Luminescence of Lanthanide and Uranyl Ions from Visible to Near‐Infrared

Treatment of Ln(NO₃)₃?nH₂O with 1 or 2 equiv 2,2′‐bipyrimidine (BPM) in dry THF readily afforded the monometallic complexes [Ln(NO₃)₃(bpm)₂] (Ln=Eu, Gd, Dy, Tm) or [Ln(NO₃)₃(bpm)₂]?THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln=Ce, Nd, Sm) yielded one of two distinct monometallic complexes, depending on the recrystallization solvent: [Ln(NO₃)₃(bpm)₂]?THF (Ln=Nd, Sm) from THF, or [Ln(NO₃)₃(bpm)(MeOH)₂]?MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO₂(NO₃)₂?6H₂O with 1 equiv BPM in THF afforded the monoadduct [UO₂(NO₃)₂(bpm)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid‐state luminescence measurements on these monometallic complexes showed that BPM is an efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the Yb^III ion emitting in the near‐IR. For Tb, Dy, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8 %, respectively. All these complexes in the solid state were stable in air.     

Triphenylphosphane Oxide Complexes of Lanthanide Nitrates: Polymorphs and Photophysics

A series of mer‐[Ln(NO₃)₃(Ph₃PO)₃] complexes were prepared from Ln(NO₃)₃ · xH₂O and Ph₃PO in chloroform (Ln = La, Nd, Sm, Eu, Gd, Tb, Dy, and Er). The La and Nd complexes were 0.25 CHCl₃ solvates, whereas the others were solvent‐free. The identical reaction using Yb(NO₃)₃ · xH₂O produced the unique salt trans‐[Yb(NO₃)₂(Ph₃PO)₄][Yb(NO₃)₄(Ph₃PO)] · Et₂O. All nitrate ions in all complexes are η²‐chelating. A comparison of the various [Ln(NO₃)₃(Ph₃PO)₃] structures, including those in the literature, reveals at least four common polymorphs, each of which is represented by isomorphic structures of multiple Ln ions. Luminescence of mer‐[Ln(NO₃)₃(Ph₃PO)₃] (Ln = Y, La, Nd, Sm, Eu, Gd, Tb, and Dy), trans‐[Yb(NO₃)₂(Ph₃PO)₄][Yb(NO₃)₄(Ph₃PO)] and Ph₃PO assignments are reported. Latva's empirical rule allows for the antenna effect, in which energy is transferred from the triplet state of the Ph₃PO ligand, to occur only for Tb³⁺. Excitation via Ph₃PO results in strong green luminescence for Tb³⁺ having twice the intensity as that which results from direct excitation of the f‐f transitions.     

Extraction of rare-earth elements from nitrate solutions by fullerene black impregnated with tetraphenylmethylenediphosphine dioxide

The distribution of trace amounts of La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between HNO₃ aqueous solutions and fullerene black (a product of electric are evaporation of graphite) impregnated with tetraphenylmethylenediphosphine dioxide (L) as a function of the concentrations of HNO₃ in the aqueous phase and L in the sorbent phase was considered. It was shown that REE(III) ions pass into the sorbent phase in the form of Ln(NO₃)₃L₃ solvated nitrates; the efficiency of extraction of these ions decreases with an increase in the REE atomic number in the periodic table.     

Synthesis and characterization of novel heteronuclear complexes of Ln(III)-Cu(II) with non-cyclic polyether Schiff base

Nine novel heteronuclear complexes of Ln(III)-Cu(II) with salicylidene tetraethylene glycol diamine (SALTTA) have been synthesized and characterized. They have the general formulae [L_nC_u2(SALTTA)₂(NO₃)₃](NO₃)₄·3H₂O (Ln=La, Pr, Nd, Sm) and [LnCu₃(SALTTA)₃(NO₃)₅]-(NO₃)₄·4H₂O (Ln=Gd, Tb, Er, Yb, Y). The IR spectra show that v_C=N in the Ln(III)-Cu(II) heteronuclear complexes are splitted up into two peaks with a far distance. It has been confirmed that oxygen atoms in oxyethylene of the ligand are not all coordinated to the central metal ions by both IR and NMR methods.     

Synthesis, characterization, thermal stability, reactivity, and antimicrobial properties of some novel lanthanide(III) complexes of 2-(N-salicylideneamino)-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Two series of new lanthanide(III) complexes of the type [Ln(HSAT)₂(H₂O)₃Cl₃] and [Ln(HSAT)₂(NO₃)₃], where Ln = La, Pr, Nd, Sm, Eu, Gd, Dy, Tm, Yb, or Lu, and HSAT = 2-(N-salicylideneamino)-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene, are synthesized by the reaction of LnCl₃ or Ln(NO₃)₃ with the title ligand in ethanol. The complexes are characterized by elemental analysis, magnetic moment values, molar conductivity, IR, UV-Vis, and ¹H NMR spectral data. Two selected complexes are subject to thermogravimetric analysis, and their kinetic parameters are estimated using Coats-Redfern equation. The complex [La(HSAT)₂(NO₃)₃] underwent facile transesterification when refluxed in methanol. The ligand and some selected complexes are screened for their antimicrobial properties. Antimicrobial activities of the ligand increase on coordination with the metal ion. The text was submitted by the authors in English.     

Adducts of aqua complexes of Ln3+ with a symmetrical octamethyl-substituted cucurbituril: potential applications for isolation of heavier lanthanides

Interaction of a series of lanthanide cations (Ln³⁺) with a symmetrical octamethyl-substituted cucurbituril (OMeQ[6]) has been investigated. X-ray single-crystal diffraction analysis has revealed that the interaction results in the formation of adducts of OMeQ[6] with aqua complexes of lanthanide cations ([Ln(H₂O)₈]³⁺), Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb in OMeQ[6]–Ln(NO₃)₃–H₂O systems. However, no solid crystals were obtained from systems containing La, Ce, Pr, Nd and Sm. X-ray diffraction analysis has revealed that although the solid adducts fall into two isomorphous groups, there are no significant differences in the interactions between OMeQ[6] and [Ln(H₂O)₈]³⁺ complexes and in the corresponding supramolecular assemblies. Thermodynamic parameters for the interaction between OMeQ[6] and [Ln(H₂O)₈]³⁺ complexes based on isothermal titration calorimetry experiments show two periods corresponding to the above two systems, with the lighter lanthanide cations preferring to remain in solution and the heavier lanthanide cations forming crystalline solids. Electron spectroscopy has shown that interaction of OMeQ[6] with lanthanide cations could provide a means of isolating heavier lanthanide cations from their lighter counterparts.     

Extraction of scandium and rare-earth elements by a phosphorylated azapodand

The interphase distribution of microamounts of nitrates and perchlorates of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu between aqueous solutions of NH₄NO₃ or NH₄ClO₄ and solutions of a phosphorylated podand [Ph₂P(O)CH₂CH₂OCH₂CH₂]₂NBu in dichloroethane was studied. The stoichiometry of extracted complexes was determined. The efficiency of metal ion transfer to an organic phase was considered as affected by HClO₄, HNO₃, and HCl concentrations in the aqueous phase and by the nature of the organic solvent. The test compounds have higher extraction capacities with respect to metal ions than neutral monodentate organophosphorus compounds.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

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Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Synthesis and characterization of rare earth complexes with Phthalaldehyde-lysine Schiff base

Ten new rare earth complexes with Schiff base (HL) derived from phthalaldehyde with two-CHO groups and lysine, which has unsymmetrical α-and ε--NH₂ groups, were synthesized and characterized by elemental analysis, TG-DTA analysis, UV-Vis, IR, and ¹H NMR spectra. They were confirmed to be as LnL₂(NO₃)·4H₂O (Ln=La, Pr, Nd, Sm, Y) and LnL₂(NO₃)·3H₂O (Ln=Gd, Tb, Dy, Er, Yb), respectively. Furthermore, their coordination mechanism, spectral properties and probable molecular structures were also discussed. __________ Translated from Journal of Zhejiang University (Science Edition), 2005, 32 (5) (in Chinese)     

Extraction of rare-earth nitrates by phosphoryl podands

The distribution of trace amounts of rare-earth nitrates between aqueous solutions of NH₄NO₃ and organic solutions of phosphoryl podands is studied for Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y. The stoichiometry of the extraction complexes is determined. The effect of the structure of the extractant and the nature of the organic solvent on the efficiency of rare-earth recovery to the organic phase is considered.     

Complexes of lanthanide nitrates with N,N-diethylantipyrine-4-carboxamide

New complexes of lanthanide nitrates with N, N-diethylantipyrine-4-carboxamide (DEAP), with the general formulae [Ln₂(DEAP)₃] [NO₃]₆ (where Ln = La, Pr, Nd, Sm, Tb, Ho, Er, Yb and Y) have been isolated and characterized by chemical analysis and various physical methods such as electrolytic conductance, IR and¹³C NMR spectral data. Electrolytic conductance values and infrared spectral studies indicate that the nitrate groups are coordinated. Infrared and¹³C NMR spectral analysis show that the ligand DEAP is coordinated to the tripositive metal ion through the diethylcarboxamide carbonyl and antipyrine carbonyl oxygens in a bidentate fashion.     

Lanthanide Contraction within a Series of Asymmetric Dinuclear [Ln2] Complexes

A complete isostructural series of dinuclear asymmetric lanthanide complexes has been synthesized by using the ligand 6‐[3‐oxo‐3‐(2‐hydroxyphenyl)propionyl]pyridine‐2‐carboxylic acid (H₃ L ). All complexes have the formula [Ln₂(H L )₂(H₂ L )(NO₃)(py)(H₂O)] (Ln=La ( 1 ), Ce ( 2 ), Pr ( 3 ), Nd ( 4 ), Sm ( 5 ), Eu ( 6 ), Gd ( 7 ), Tb ( 8 ), Dy ( 9 ), Ho ( 10 ), Er ( 11 ), Tm ( 12 ), Yb ( 13 ), Lu ( 14 ), Y ( 15 ); py=pyridine). Complexes of La to Yb and Y have been crystallographically characterized to reveal that the two metal ions are encapsulated within two distinct coordination environments of differing size. Whereas one site maintains the coordination number (nine) through the whole series, the other one increases from nine to ten owing to a change in the coordination mode of an NO₃^? ligand. This series offers a unique opportunity to study in detail the lanthanide contraction within complexes of more than one metal. This analysis shows that various representative parameters proportional to this contraction follow a quadratic decay as a function of the number n of f electrons. Slater’s model for the atomic radii has been used to extract, from these decays, the shielding constant of 4f electrons. The average of O???O distances within the coordination polyhedra shared by both metals and of the Ln???Ln separations follow also a quadratic decay, therefore showing that such dependence holds also for parameters that receive the contribution of two lanthanide ions simultaneously. The magnetic behavior has been studied for all nondiamagnetic complexes. It reveals the effect of the spin–orbit coupling and a weak antiferromagnetic interaction between both metals. Photoluminescent studies of all the complexes in the series reveal a single broad emission band in the visible region, which is related to the coordinated ligand. On the other hand, the Nd, Er, and Yb complexes show features in the near‐IR region due to metal‐based transitions.     

Different Types of Coordinated Urea Molecules in its Complexes with Rare‐Earth Iodides and Perchlorates

An earlier reported series of the [Ln(Ur)₄(H₂O)₄]I₃ (Ln = Y, La, Nd, Eu, Gd, Dy, Ho, Er; Ur = urea) complexes was completed with seven new compounds (Ln = Ce, Pr, Sm, Tb, Tm, Yb, Lu); one of them, [Ce(Ur)₄(H₂O)₄]I₃, was studied by X‐ray diffraction. The most striking feature of the [Ln(Ur)₄(H₂O)₄]I₃ structures is the presence of two types of coordinated urea molecules. There are two planar symmetric and two non‐planar asymmetric urea molecules. The Ln–O–C bond angles vary in the ranges 163.06–165.71° and 148.42–152.42° for symmetric and asymmetric urea ligands, respectively, correlating with the ionic mode of urea coordination. To elucidate the role of aqua ligands for the urea coordination mode, two water‐free perchlorate complexes, [La(Ur)₈](ClO₄)₃ · 2Ur and [La(Ur)₇(OClO₃)](ClO₄)₂ were synthesized and structurally characterized. In these complexes, all urea molecules are planar symmetric; however, both covalent and ionic types of urea coordination with the La–O–C bond angles varying in the 132.4–142.3° and 145.5–159.1° ranges, respectively can be observed.     

Heteroleptic polypyrazolylborate derivatives of the lanthanide ions. The synthesis of acetylacetonate derivatives and the molecular structures of [Ln{HB(C3N2H3)3}2{MeC(O)CHC(O)Me}] (Ln = Ce,Yb)

The air and moisture stable complexes [Ln{HB(C₃N₂H₃)₃}₂{MeC(O)CHC(O)Me}] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, Lu, Y), have been prepared and characterized. The molecular structures of the compounds with Ln = Ce and Yb reveal that a substantial distortion of the coordination geometry found for Ce³⁺ is necessary to allow the ligand set to accommodate the smaller Yb³⁺ ion.     

Studies on synthesis and magnetic resonance of lanthanide complexes with novel Schiff base derived from noncyclic polyether and β-diketone

Nine h( III) complexes with a novel Schiff base derived from diglycolamine and benzoylacetone (BZDA) have been synthesized and characterized. They can be formulated as [Ln₂(BZDA)₃(NO₃)₃](NO₃)₃-nH₂O (Ln? La, Pr, Nd, Sm, n = 4; Ln = Gd, Tb, Er, Yb, Y, n = 7). Enamic form mechanism in this β-diketone Schiff base and its Complexes were suggested and proved by IR, UV and NMR methods. The ¹³C spin-lattice relaxation time T₁ and the ratios of r(C_i-In)/ ^r (c_j-in) were measured by a 500 MHz NMR instrument for elucidating the formation of the stable six-membered chelate ring structure in these complexes. The EPR spectrum of the Gd( III) complex exhibits the “U” spectral feature and “zero field effect”. On the basis of them, the crystal field strength and the local symmetry around Gd ³⁺ in the complex have been discussed.     

Complexes of lanthanide nitrates with 4n-(2′-hydroxy benzylidene)-aminoantipyrine

New complexes of lanthanide nitrates with 4N-(2′-hydroxy benzylidene)-aminoantipyrine (HBAAP) having the general formula [Ln(HBAAP)₂(NO₃)₃] (where Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y) have been prepared and characterized. Conductance studies indicate non-electrolytic behaviour for these complexes. Their infrared spectra show that both the ligand and the nitrate group are bound to the metal ion in a bidentate fashion. Electronic spectra indicate weak covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to ～200°C and undergo complete decomposition in the range 200–550° resulting in the formation of the stable lanthanide oxides.     

Extraction of rare earth elements with 2-[2'-(methoxydiphenylphosphoryl)phenyldiazenyl]-4-<Emphasis Type="Italic">tert</Emphasis>-butylphenol in the presence of 1-butyl-3-methylimidazolium and trioctylmethylammonium picrates

Extraction of micro amounts of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y with solutions of 2-[2'-(methoxydiphenylphosphoryl)phenyldiazenyl]-4-tert-butylphenol in 1,2-dichloroethane in the presence of 1-butyl-3-methylimidazolium and trioctylmethylammonium picrates has been studied. The stoichiometry of extracted complexes has been determined, the effect of HNO₃ concentration in aqueous phase on the efficiency of rare earth elements recovery into organic phase has been considered.