Mixed chelates of some trivalent lanthanide ions containing (trans-1,2-cyclhexylenedinitrilo)tetraacetate and norleucinate

Summary Formation constants of mixed chelates with (trans-1,2-cyclohexylenedinitrilo)tetra-acetate (DCTA) as primary ligand and norleucinate (nle) as secondary ligand with metal ions La(III), Ce(III), Pr(III), Sm(III), Gd(III), Tb(III), Dy(III), Er(III), and Yb(III) have been determined by the modified potentiometricpH titration method of Irving-Rossotti in aqueous medium at (295±1) K and fixed ionic strength of =0.1M (NaClO₄). Formation constants of binary complexes of the metal ions with the secondary ligand have also been determined under identical conditions. The mixed chelates were found to be more stable than the binary ones. The order of stabilities in terms of metal ions is La(III)Gd(III)

Gemischte Chelate einiger dreiwertiger Lanthanidenionen mit (trans-1,2-Cyclohexylendinitril)tetraacetat und Norleucinat

Zusammenfassung Es wurden die Komplexbildungskonstanten gemischter Chelate mit (trans-1,2-Cyclohexylendinitril)tetraacetat als Primärkomponente und Norleucinat als Sekundärkomponente mit den Metallionen La(III), Ce(III), Pr(III), Sm(III), Gd(III), Tb(III), Dy(III), Er(III) und Yb(III) mittels einer modifizierten potentiometrischen Titrationsmethode nach Irving-Rossotti in wäßrigem Medium bei (295±1) K und einer konstanten Ionenstärke von =0.1M (NaClO₄) bestimmt. Die Bildungskonstanten der binären Komplexe der Metallionen mit dem Sekundärliganden wurden ebenfalls unter identen Bedingungen bestimmt. Es wurde festgestellt, daß die gemischten Chelate stabiler sind als die binären. Die Stabilitätsreihenfolge bezüglich der Metallionen ist La(III)Gd(III)     

Radiationless transitions in trivalent lanthanide ions embedded in solids

Radiationless transitions in lanthanide ions embedded in glassy and crystalline hosts have been briefly reviewed. The correlations of multiphonon relaxation rates with energy gaps, vibrational frequencies, temperatures and electronic symmetries have been discussed. The essence of various theories, such as Nth order methods, non-adiabatic Hamiltonian method, dynamic coupling model has also been presented.     

Thermogravimetric and spectroscopic characterization of trivalent lanthanide chelates with some schiff bases

Solid complexes of two derivatives of Schiff bases SAT and SAZ with Pr(III), Nd(III), Gd(III), Dy(III), Ho(III), Er(III) and Yb(III) were prepared and characterized by elemental analysis , IR spectra and TG. The suggested formula of the obtained solid complexes is [MLCl₂(H₂O)n] for sat and [MLCl (H₂O)n] for SAZ where M=trivalent lanthanide ion, L=deprotonated ligand and n=2-3. The TG gives information about the coordinated water molecules, thermal stability and the coordination number of M which was found to be 6–8. A scheme of thermal decomposition of the complexes is also proposed. Comparison of the IR spectra of the ligands with those of their complexes indicate the center of chelation in SAT and SAZ which act as tridentate ligands. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of stability constants of some substituted 4-pyrazolone dyes containingo-methoxy,o-carboxy,ando-nitro groups with trivalent lanthanide ions

The relative stabilities of the metal derivatives of hydrazo pyrazolone dyes containingortho -OCH₃, -COOH, and -NO₂ groups have been measured potentiometrically in 75% (v/v) dioxane—water mixture at 30 °C and <0.1 ionic strength. The stability constant of their 1:1 and 1:2 chelates with twelve trivalent lanthanide ionsLn(III) have also been determined. The effects of substituents on the hydrazo-moiety of the ligand on the equilibria are discussed. The affinity of different ligands for complexation with lanthanide ions reaches its highest value withortho-carboxyphenylhydrazopyrazolone. The data were correlated and the results were used to explain the stabilization of such chelates by dative -bonding betweenLn(III) and the ligand.

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Bestimmung der Stabilitätskonstanten einigero-Methoxy-,o-Carboxy undo-Nitro-substituierter 4-Pyrazolon-Farbstoffe mit trivalenten Lanthanidenionen

Zusammenfassung Es wurden die relativen Stabilitäten der Metallderivate von Hydrazopyrazolon-Farbstoffen mitortho-OMe, -COOH und -NO₂ potentiometrisch in 75% (v/v) Dioxan—Wasser bei 30 °C und einer Ionenstärke <0.1 bestimmt. Die Stabilitätskonstanten der 1:1 und 1:2 Chelate mit zwölf trivalenten LanthanidenionenLn(III) wurden ebenfalls gemessen. Die Substituenteneffekte werden diskutiert. Dabei zeigeno-Carboxyphenylhydrazopyrazolone die höchste Affinität zu Lanthanidenionen. Die Daten werden miteinander korreliert und die Resultate auf der Basis einer dativen -Bindung zwischenLn(III)-Ion und dem Liganden diskutiert.

     

Interactions between metal ions and carbohydrates. Spectroscopic characterization and the topology coordination behavior of erythritol with trivalent lanthanide ions

The coordination of carbohydrate to metal ions is important because it may be involved in many biochemical processes. The synthesis and characterization of several novel lanthanide-erythritol complexes (TbCl(3)·1.5C(4)H(10)O(4)·H(2)O (TbE(I)), Pr(NO(3))(3)·C(4)H(10)O(4)·2H(2)O (PrEN), Ce(NO(3))(3)·C(4)H(10)O(4)·2H(2)O (CeEN), Y(NO(3))(3)·C(4)H(10)O(4)·C(2)H(5)OH (YEN), Gd(NO(3))(3)·C(4)H(10)O(4)·C(2)H(5)OH (GdEN)) and Tb(NO(3))(3)·C(4)H(10)O(4)·C(2)H(5)OH (TbEN) are reported. The structures of these complexes in the solid state have been determined by X-ray diffraction. Erythritol is used as two bidentate ligands or as three hydroxyl group donor in these complexes. FTIR spectra indicate that two kinds of structures, with water and without water involved in the coordination sphere, were observed for lanthanide nitrate-erythritol complexes. FIR and THz spectra show the formation of metal ion-erythritol complexes. Luminescence spectra of Tb-erythritol complexes have the characteristics of the Tb ion.     

Coordination chemistry of trivalent lanthanide and actinide ions in dilute and concentrated chloride solutions

We have used EXAFS spectroscopy to investigate the inner sphere coordination of trivalent lanthanide (Ln) and actinide (An) ions in aqueous solutions as a function of increasing chloride concentration. At low chloride concentration, the hydration numbers and corresponding Ln,An-O bond lengths are as follows: La3+, N = 9.2, R = 2.54 A; Ce3+, N = 9.3, R = 2.52 A; Nd3+, N = 9.5, R = 2.49 A; Eu3+, N = 9.3, R = 2.43 A; Yb3+, N = 8.7, R = 2.32 A; Y3+, N = 9.7, R = 2.36 A; Am3+, N = 10.3, R = 2.48 A; Cm3+, N = 10.2, R = 2.45 A. In ca. 14 M LiCl, the early Ln3+ ions (La, Ce, Nd, and Eu) show inner sphere Cl- complexation along with a loss of H2O. The average chloride coordination numbers and Ln-Cl bond lengths are as follows: La3+, N = 2.1, R = 2.92 A; Ce3+, N = 1.8, R = 2.89 A; Nd3+, N = 1.9, R = 2.85 A; Eu3+, N = 1.1, R = 2.81 A. The extent of Cl- ion complexation decreases going across the Ln3+ series to the point where Yb3+ shows no Cl- complexation and no loss of coordinated water molecules. The actinide ions, Am3+ and Cm3+, show the same structural effects as the early Ln3+ ions, i.e., Cl- ion replacement of the H2O at high chloride thermodynamic activities. The Clion coordination numbers and An-Cl bond lengths are: Am3+, N = 1.8, R = 2.81 A; Cm3+, N = 2.4, R = 2.76 A. When combined with results reported previously for Pu3+ which showed no significant chloride complexation in 12 M LiCl, these results suggest that the extent of chloride complexation is increasing across the An3+ series. The origin of the differences in chloride complex formation between the Ln3+ and An3+ ions and the relevance to earlier work is discussed.     

Squarate complexes of some lanthanide ions in aqueous solution

The squarate complexes of Eu³⁺, Tb³⁺ and Tm³⁺ in aqueous solutions of 0.05M, 0.075M and 0.1M ionic strength are studied using the solvent extraction method. Effects of changes in the ionic strength on the stability constants of the complexes formed are discussed.     

Structural features of thiocarbamide derivatives of some lanthanide iodides

Data on the synthesis, IR spectroscopy, and single crystal XRD are presented for thiocarbamide compounds of the composition [Ln(H₂O)₉]I₃·2CS(NH₂)₂, where Ln = Dy (I) and Yb (II). The structural features of [Ln(H₂O)₉]I₃·2CS(NH₂)₂ (Ln = Pr, Nd, Eu, Gd, Dy, Ho, Er, and Yb) are discussed. The compounds of thiocarbamide with Pr, Nd, Eu, Gd, and Dy iodides are found to form the first isostructural series characterized by a continuous network structure, while with Ho, Er, and Yb iodides the second isostructural series with a layered type structure is formed.     

Potentiometric studies on the complexation equilibria between some trivalent lanthanide metal ions and biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS)

Summary The chelation behaviour of some trivalent lanthanide and yttrium metal ion with biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS) has been investigated by potentiomotric measurements at 20±0.5°C in 75% (v/v) dioxane-water medium at various ionic strengths of sodium perchlorate. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of (average number of ligand bound per metal ion) andpL (free ligand exponent). The formation constants of metal chelates have been computed on a PC-XT computer, using a program patterned after that of Sullivan et al. to give _n values using weighted least squares method. TheS _min values (S _min =²) have been calculated. The order of formation constants of chelates was found to be: La³⁺3+3+3+3+3+3+3+3+3+. The formation constants of the chelates formed have been correlated to size and ionization potentials of the metal ions.

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Potentiometrische Untersuchungen der Komplexierungsgleichgewichte zwischen einigen trivalenten Metallionen und biologisch aktivem 2-Hydroxy-1-naphthaldehyd-thiosemicarbazon (HNATS)

Zusammenfassung Es wurde das Chelierungsverhalten einiger trivalenter Lanthanidenionen mit biologisch aktivem 2-Hydroxy-1-naphthaldehyd-thiosemicarbazon (HNATS) mittels potentiometrischer Messungen bei 20±0.5°C in 75% (v/v) Dioxan-Wasser bei verschiedener Ionenstärke an Natriumperchlorat untersucht. Die Methode nach Bjerrum und Calvin in der Modifikation nach Irving und Rossotti wurde zur Ermittlung der Werte (mittlere Anzahl an Liganden pro Metallion) undpL (Exponent an freiem Liganden) verwendet. Die Komplexbildungskonstanten wurden in Anlehnung an Sullivan et al. an einem PC-XT Computer errechnet. DieS _min-Werte (S _min=²) wurden ebenfalls bestimmt. Die Reihung der Chelatbildungskonstanten war: La³⁺3+3+3+3+3+3+3+3+3+. Die Bildungskonstanten sind mit der Größe und dem Ionisierungspotential der Metallionen zu korrelieren.

     

Liquid-liquid extraction of some lanthanide metal ions by polyoxyalkylene systems

Polyoxyalkylene systems, namely, polypropylene glycol (PPG-1025), polyethylene glycol (PEG-600) and polybutadieneoxide (PBDO-700) dissolved in either nitrobenzene or 1,2-dichloroethane have been tested as prospective extractants for some lanthanide metal ions (Eu(3+), Pr(3+) and Er(3+)) from their aqueous solutions in the presence of picrate anions. The metal ions were quantified before and after extraction using the inductively coupled plasma emission spectrophotometry technique. The percent extraction and the distribution coefficients have indicated that pH of the aqueous phase, picrate concentration and the organic solvent are the major parameters that affect the extraction efficiency of the metal ions. The optimum pH range was found to be 3.5-5.5 and the picrate concentration should be as high as possible; however, a picrate concentration of about 0.05 M proved to be adequate for a near quantitative extraction. In all cases, nitrobenzene enhanced a higher percent extraction compared to 1,2-dichloroethane. The efficiency of the polyoxyalkylene systems to extract certain lanthanide metal ions was in the order PBDO-700>PPG-1025>PEG-600 when nitrobenzene was the organic solvent and in the order PPG-1025>PBDO-700 approximately PEG-600 when 1,2-dichloroethane used as the solvent in the organic phase. The extractability of PPG-1025 towards the lanthanide metal ions was in the order Pr(3+)>Eu(3+)>Er(3+) irrespective of the organic solvent used. The stoichiometry of the extracted polyoxyalkylene ion-pairs with the lanthanide metal ions has been estimated. Each mole of metal ions is associated with three moles of picrate anions and 13 to 14 moles of propyleneoxide units in the case of PPG-1025, and about 9 to 10 moles of ethyleneoxide units in the case of PEG-600 and 10 moles of butadieneoxide units in the case of PBDO-700.     

Hydration of some trivalent metal ions extracted as perchlorates with trioctylphosphine oxide in hexane

Perchlorates of Sc³⁺, Y³⁺, La³⁺, and Eu³⁺ have each been extracted from 0.1 mol·dem^?3 aqueous solution of μ□=1 with trioctylphosphine oxide (TOPO) in hexane. The hydration number of the extracted salts has been determined by Karl Fischer titration. Sc³⁺, Y³⁺ and EU³⁺ are extracted as the tetra- and hexa-solvates of TOPO but the assumption of octa-solvate on addition to the tetra-solvate explains the extraction data of La³⁺ well. The hydration number of tetra-solvates is 2 (Sc³⁺ and Eu³⁺), 3 (Y³⁺) and probably 4 for La³⁺ ion. That of hexa- and octa-solvates is 4–5.     

On the flocculation and re-dissolution of trivalent lanthanide metal ions by sodium dodecyl sulfate in aqueous solutions

The interaction between aqueous solutions of trivalent lanthanide ions (M(3+): La(III) and Gd(III) and Tb (III)) at fixed (1mM) concentrations and various concentrations of sodium dodecyl sulfate (SDS), ranging from pre- to post-micellar, has been investigated by ICP-AES (La(III) and Gd(III)), luminescence spectra (Gd(III)) and lifetimes (Tb(III)) and (139)La NMR spectroscopy. It has been found that at concentration ratios, r=[SDS]/[M(3+)], around the charge neutralization value (ca. 3), dodecyl sulfate (DS(-)) anion interacts with the metal ions to form insoluble aggregates. The metal ion-DS(-) complexes remain flocculated for r values below 5-6 (Gd(III) and La(III), respectively), while at higher r values, re-dissolution takes place. The flocculated aggregates have been characterized by X-ray powder diffraction, and show a lamellar structure. Job plot method indicates that a complex with a 1:3 (M(3+):DS(-)) stoichiometry is formed. From ICP-AES analysis, a model based on a three-step mechanism has been developed and association constants calculated. For all systems the interaction between DS(-) and metal ions follows an associative process with K values ranging between K(1)=10 and K(3)=10(4). These data are discussed on the basis of the physical-chemical characteristics of the metal ions. Re-dissolution with increasing surfactant concentration is attributed to formation of mixed lanthanide/sodium dodecyl sulfate aggregates, with the relative lanthanide fraction in these species decreasing with increasing SDS concentration.     

Interaction between metal nitrates and carbohydrates: the topology coordination behavior of galactitol with trivalent lanthanide and divalent alkaline earth ions

It has long been known that metal ions and saccharides are involved in many biochemical processes. In this paper, metal nitrates were used as reactants to detect the coordination structures of the hydroxyl groups of galactitol in different environments. Three novel crystal structures and FT-IR spectra of metal nitrate-galactitol complexes of La(NO3)3.C6H14O6.(4)H2O, 2Ca(NO3)2.C6H14O6.H2O, and Sr(NO3)2.C6H14O6 were examined in an effort to clarify the structural factors that control metal ion interactions with saccharides in aqueous and biological systems. The coordination structures of galactitol with alkaline earth and lanthanide nitrates in the solid state were compared using FT-IR, Raman, and X-ray diffraction techniques to extensively discuss the coordination rules of different kinds of metal ions. Results provided a model of the coordination sites found in sugars and showed that the introduction of NO3- made the coordination modes of galactitol more diverse and complex than those of the corresponding chloride complexes. Specifically, new coordination modes of galactitol and complicated topology networks were found in 2Ca(NO3)2.C6H14O6.H2O and Sr(NO3)2.C6H14O6. FT-IR results are consistent with the crystal structures and thus provide the possibility of using the similarity of IR spectra to speculate about unknown structures when the compounds are difficult to prepare as single crystals.     

Synthesis of a novel dinucleating aminocarboxylate macrocycle and structures of its dinuclear complexes with di- and trivalent transition and lanthanide metal ions

The synthesis of the new ligand L1(H4L1= 3,8,16,21-tetrakis(carboxylmethyl)-3,8,16,21,27,28-hexaazatricyclo[21.3.1.1(10,14)]octacosa-1(27),10,12,14(28),23,25-hexaen-5,18-diine) is reported. The solid-state structures of the four homodinuclear chelate complexes, [Zn2(L1)(H2O)2] x 6H2O, [Fe2(L1)(mu-O)] x 4H2O, [La2(L1)(NO3)2(H2O)2] x 6H2O and Na[Eu2(L1)(mu-AcO)3] x 3H2O, were determined by single-crystal X-ray structural analysis.     

Reductive ability of 1,4-dihydropyridine derivatives in relation to ions of trivalent iron

3,5-Dicarbonyl derivatives of 2,6-dimethyl-1,4-dihydropyridine (1,4-DHP) can reduce Fe³⁺ to Fe²⁺ depending on the nature of the substituents at position 4 and in the 3,5-ester group. This ability is less pronounced for the 1,4-DHP derivatives investigated than for ascorbic acid, but among derivatives possessing antioxidant activity it is less than that of the known antioxidants ionol (BOT) and trolox. Latvian Institute of Organic Synthesis, Riga, LV-1006, Latvia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 661–663, May, 1999.     

Complexes of lanthanide ions with dibenzodioxatetraazamacrocyclic ligands

Efficiency of luminescence of europium and ytterbium ions in complexes with three 16-membered dibenzodioxatetraazamacrocycles was estimated.     

Separation and determination of some trivalent metal ions using rhodamine B grafted polyurethane foam

The incorporation of rhodamine B into polyurethane foam matrix was prepared by mixing the rhodamine B with polyol (polyether) prior to the addition of diisocyanate reagent to form the polyurethane foam material. Rhodamine B grafted polyurethane foam (Rod.B-PUF) was found to be very suitable for the separation and preconcentration of trivalent metal ions e.g. bismuth (III), antimony (III) and iron (III) from thiocyanate solutions. Bismuth and antimony were separated from concentrated acid medium (1–6 M H₂SO₄). Iron (III) was separated from pH 1 to 3. The kinetics of sorption of the Bi (III), Sb (III) and Fe (III) onto the Rod.B-PUF was found to be fast, the extraction is accomplished from 5 to 10 min with average values of half-life of sorption (t_1/2) of 2.9 min. The average values of the Gibbs free energy (ΔG) for the sorption of metal ions onto Rod.B-PUF are ?6.6 kJ mol^?1, which reflect the spontaneous nature of sorption process. The sorption mechanism of the metal ion onto Rod.B-PUF was also discussed.