Complexes of the Lighter Lanthanoid Nitrates with 15-crown-5 and 18-crown-6 ethers: Synthesis and characterization

Complexes of lanthanoid trinitrates Ln(NO₃)₃ with 15-crown-5 ether 1 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and with 18-crown-6 ether 2 (Ln = La, Ce, Pr, Nd) having a 1:1 stoichiometry as well as 4:3 complexes with 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. All the isolated complexes are solvent free. At 170–220° the 1:1 complexes of 2 are quantitatively transformed into 4:3 complexes. X-Ray powder diagrams of the neodymium complexes with 2 indicate that both the 1:1 and 4:3 complexes are genuine compounds. All the 1:1 complexes show a characteristic IR. absorption band at 875–880 cm^?1 absent from both the spectra of the free ligands and of the 4:3 complexes. The spectroscopic properties (IR. and electronic spectra, fluorescence lifetimes) of the complexes and the low magnetic moments of the Ln(III) ions in the complexes with Ln = Ce-Eu are indicative of a strong interaction between the lanthanoid ions and the crown ethers 1 and 2 .     

A Solution State Study of the Complexation and Thermodynamic Parameters of Binary Complexes of the Inner Transition Metals with Piracetam in Aqueous and Mixed Solvents

An equilibrium study on complexation behavior of the inner transition metals, where M = {Y(III), La(III, Ce(III, Pr(III), Nd(III), Sm(III), Gd(III), Dy(III), Th(IV)} and L = piracetam, has been carried out using the Irving–Rossotti titration technique in aqueous media at different temperatures and ionic strengths. The protonation constant and stability constants (log₁₀ β _n ) of the resulting inner metal–ligand complexes have been calculated with the Fortran IV program BEST using the method of least squares and considering the BESTFIT model. Thermodynamic parameters were also evaluated, yielding negative ΔG°, ΔH° and positive ΔS° values that indicate complex formation is favorable at ordinary temperatures. Species distribution curves of complexes have been plotted as function of pH using the SPEPLOT FORTRAN IV program to visualize the presence of various species in equilibrium in the pH range 2–6. To understand more about these equilibria, the stability of these complexes was studied at different percentages of solvent (10–30 % v/v) in different aqua-organic solvent mixtures with methanol, ethanol, 1-butanol and dimethylformamide.     

Thermal and spectroscopic studies of sodium and light lanthanide (III) complexes with 2,4-pyridinedicarboxylate anion

Pyridine-2,4-dicarboxylic acid (lutidinic acid) is next one after pyridine-2,5-dicarboxylic acid of the six isomers which lanthanide complexes were studied thermally and spectrally. New complexes synthesized with light lanthanides (III) with general formula Ln₂L₃·nH₂O, where n?=?7.5; 8; 8.5; 9, were obtained. Sodium salt was obtained as hexahydrated compound. Hydrated complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), and Gd(III) are thermally stable up to 303?C313?K. Dehydration process run for all compounds in one stage, anhydrous compounds decompose through appropriate light lanthanides (III) oxalates, oxocarbonates, carbonates to metal oxides. Theoretical IR and Raman studies were carried out in order to identify precisely characteristic group bands vibrations present on IR and Raman spectra.     

Synthesis and some properties of light lanthanide complexes with 4,4′-bipyridine and dibromoacetates

In this study, new complexes with formulae: Ce(4-bpy)(CHBr₂COO)₃·H₂O, Ln(4-bpy)_0.5(CHBr₂COO)₃·2H₂O (where Ln(III) = Pr, Nd, Sm; 4-bpy = 4,4′-bipyridine) and Eu(4-bpy)(CHBr₂COO)₃·2H₂O were prepared, and characterized by chemical and elemental analyses, and IR spectroscopy. The way of metal–ligand coordination was discussed. They are small crystalline. The complexes of Pr(III), Nd(III), and Sm(III) are isostructural in group. Conductivity studies (in methanol, dimethylformamide, and dimethylsulfoxide) were also performed and described. The thermal properties of complexes in the solid state were studied using TG–DTG techniques under dynamic flow of air atmosphere. TG–MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolyses of Ce(III) and Sm(III) complexes in dynamic flow of air atmosphere.     

Some lanthanide metal complexes of n-isonicotinamidosalicylaldimine

Trivalent lanthanide complexes of the type K[ML ₂] whereM=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III) and Dy(III) and H₂ L=N-isonicotinamidosalicyladimine, have been prepared and characterised. The nephelauxetic ratio (β), covalency (δ) and bonding parameter (b ²) of K[NdL ₂] have been calculated. Infrared spectral studies reveal that N-isonicotinamidosalicylaldimine acts as a dibasic tridentate ligand. A coordination number six has been proposed for the lanthanide metal ions.     

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)     

Thermal decomposition of light lanthanide diglycolates

The conditions of thermal decomposition of La, Ce(III), Pr, Nd, Sm, Eu and Gd diglycolates have been studied. On heating, the diglycolates of Ce(III), Pr, Eu and Gd lose crystallization water and yield anhydrous salts, which are then transformed into oxides. The diglycolates of La, Nd and Sm are decomposed in three stages. First, the diglycolates undergo dehydration to form the anhydrous salts, which are next decomposed to Ln₂O₂CO₃. In the last step the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ takes place, accompanied by an endothermic effect.     

A Novel Architecture of a Heptadentate Macroacyclic 2,6-Bis [(3-methoxy salicylidene) Hydrazino carbonyl] Pyridine Towards Lanthanides: A Synthetic and Structural Studies of Dinuclear Lanthanide (III) Complexes

Reaction of Ln(NO₃)₃ with 2,6-bis[(3-methoxysalicylidene)hydrazino carbonyl]pyridine (BMSPD) afforded binuclear complexes of the type [Ln₂(BMSPD)(NO₃)₂(H₂O)₅]·3H₂O in case of La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III), and [Ln₂(BMSPD)(NO₃)₂(H₂O)₅] in case of Y(III). The mode of coordination of ligand and the conformational changes on complexation with lanthanides was studied based on elemental analysis, magnetic studies, TG/DTA, IR, ¹H-NMR, Electronic, EPR and Fluorescence spectral studies. The ligand coordinates to one metal centre through enolized deprotonated carbonyls and pyridine nitrogen whereas doubly deprotonated phenolate oxygens and two hydrazonic nitrogens ligate to another lanthanide centre. Both the metal ions are in eight-coordination environments. The ligand and complexes were further tested for antifungal and antibacterial activities.     

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.     

Thermal decomposition of lanthanide(III) complexes of bis-(salicylaldehyde)-1,3-propylenediimine Schiff base ligand

The thermal decomposition of lanthanide complexes, with a general formula: [LnL(NO₃)₂](NO₃), where Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, and Er; and L = bis-(salicyladehyde)-1,3-propylenediimine Schiff base ligand, was studied by thermogravimetric (TG) and derivative thermogravimetric (DTG) techniques. The TG and DTG data indicated that all complexes are thermostable up to 398 K. The thermal decomposition of all Ln(III) complexes was a two-stage process and the final residues were Ln₂O₃ (Ln = La, Nd, Sm, Gd, Dy, Er), Tb₄O₇, and Pr₆ O₁₁. The activation energies of thermal decomposition of the complexes were calculated from analysis of the TG-DTG curves using the Kissinger, Friedman, and Flynn-Well-Ozawa methods.     

3-Picoline-N-oxide complexes of rare-earth bromides

3-Picoline-N-oxide (3-PicNO) complexes of rare-earth bromides of the formulaMBr₃(3-PicNO)_8–n·nH₂O wheren=0 forM=La, Pr, Nd, Sm Tb or Y andn=2 forM=Ho or Yb have been prepared. Infrared and proton NMR studies indicate that the coordination of the ligand is through oxygen. Conductance data in acetonitrile suggest that two bromide ions are coordinated to the metal ion. Proton NMR studies suggest a bicapped dodecahedral arrangement of the ligands around the metal ion in solution for Pr(III), Nd(III) and Tb(III) complexes.     

Thermal decomposition of rare earth element suberates in air atmosphere

The condition of thermal decomposition of La, Ce(III), Pr(III), Nd, Sm, Eu(III), Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu suberates were studied. The suberates of Ce(III), Sm, Eu(III), Ho, Tm, Yb and Lu heated lose crystallization water. Anhydrous Sm and Eu(III) suberates decompose to oxides with intermediate formation Ln₂O₂CO₃, whereas suberates of other lanthanides decompose directly to oxides. Suberates of La, Pr(III), Nd, Gd, Tb, Dy and Er lose some water molecules and then decompose directly to oxides. Only La complex decomposes to La₂O₃ via the intermediate formation La₂O₂CO₃.

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Zusammenfassung Es wurden die UmstÄnde der thermischen Zersetzung von La-, Ce(III)-, Pr(III)-, Nd-, Sm-, Eu(III)-, Gd-, Tb-, Dy-, Ho-, Er-, Tm-, Yb- und Lu-suberat untersucht. Bei Erhitzen verlieren Ce(III)-, Sm-, Eu(III)-, Ho-, Tm-, Yb- und Lu-suberat Kristallwasser. Wasserfreies Sm-bzw. Eu(III)-suberat zersetzt sich über das Zwischenprodukt der Zusammensetzung Ln₂O₂CO₃ zum Oxid, wÄhrend sich die Suberate der anderen Lanthanoide direkt zu den Oxiden zersetzen. La-, Pr(III)-, Nd-, Gd-, Tb-, Dy- und Er-suberat geben einige Moleküle Kristallwasser ab und zersetzen sich dann direkt zu den Oxiden. Nur der Lanthankomplex zersetzt sich zu La₂O₃ über das Zwischenprodukt La₂O₂CO₃.

     

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.     

Synthesis and luminescence properties of the Pr(III), Sm(III), Eu(III), Nd(III), and Yb(III) complexes with propane-1,3-dione derivatives

The luminescence method, mass spectrometry, and elemental analysis are used to reveal that under optimal conditions (pH 5–8) Ln³⁺ ions (Ln = Pr, Sm, Eu, Nd, and Yb) with 1-(2-hydroxy-4-methylphenyl)-3-(5-methyl-1-phenyl-¹ H-1,2,3-triazol-4-yl)propane-1,3-dione form complexes with the mole ratio Ln: ligand = 2: 3. According to the IR spectral data, Ln³⁺ ions coordinate three oxygen atoms of two carbonyl groups and one hydroxyl group. In the IR spectra of the complexes, an intense band at 628.7 cm^?1 is assigned to the Ln-O bond vibrations. The X-ray diffraction patterns of the complexes contain no lines corresponding to the ligand. The luminescence intensity of the complexes in the visible spectral range changes in the series Eu(III) > Sm(III) > Pr(III), whereas in the IR region the order is Yb(III) > Nd(III). In all cases, luminescence of the solid complexes is considerably more intense than that of their solutions.     

Synthesis,spectral characterization,crystal structures of lanthanide(III) pyrrolidine dithiocarbamate complexes and their catalytic activity

A series of lanthanide(III) pyrrolidine dithiocarbamate complexes [Ln(Pyrrol-Dtc)₃(Phen)] {Pyrrol-Dtc = pyrrolidine dithiocarbamate; Phen = 1,10-phenanthroline; Ln = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Er(III)} have been synthesized and structurally characterized. The molecular structures of [La(Pyrrol-Dtc)₃(Phen)], [Pr(Pyrrol-Dtc)₃(Phen)], [Sm(Pyrrol-Dtc)₃(Phen)], and [Dy(Pyrrol-Dtc)₃(Phen)] have been confirmed using single crystal XRD studies. The results reveal that in these complexes, the central Ln(III) ion is coordinated to three Pyrrol-Dtc and one Phen and possesses a distorted dodecahedron geometry. Catalytic activity of these complexes in trimethylsilylcyanation reaction has been studied.     

X-ray fluorescence determination of La,Ce, Pr,Nd, and Sm in industrial sediments of calcium sulfate using linear regression analysis

Industrial sediments of calcium sulfate semihydrate obtained from industrial extraction phosphoric acid and containing 0.3–4.5 wt % of impurity La?Sm are investigated by energy-dispersive X-ray fluorescence analysis (XRFA) and a procedure for the quantitative determination of cerium lanthanides in the sediments is developed. The use of linear regression analysis of X-ray fluorescence spectra of multielement industrial samples and models of individual compounds NaLn(SO₄)₂ · H₂O (cp grade) allowed us to resolve overlaps of spectral L-series lines for La–Sm, eliminate the background, and perform the regression assessment of line intensities of these elements. On this basis, we developed a procedure for the determination of La, Ce, Pr, Nd, and Sm in CaSO₄ · 0.5H₂O sediments with limits of detection (wt %): 0.022, 0.013, 0.011, 0.008, and 0.008, respectively. In concentration ranges (wt %) La (0.05–0.99), Ce (0.1–4.9), Pr (0.005–0.49), Nd (0.02–0.99), and Sm (0.005-0.19), the relative standard deviation RSD (n = 10, P = 0.95) was 18?27, 9?18, 20?31, 17?26, and 19?31%, respectively. A comparison of the results of XRFA with the data of inductively coupled plasma mass spectrometry confirms the accuracy of the results obtained according to OST (Branch Standard) 41-08-221-04.     

Syntheses, characterization, biological activity and fluorescence properties of bis-(salicylaldehyde)-1,3-propylenediimine Schiff base ligand and its lanthanide complexes

Eight new lanthanide metal complexes [LnL(NO(3))(2)]NO(3) {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, L = bis-(salicyladehyde)-1,3-propylenediimine Schiff base ligand} were prepared. These complexes were characterized by elemental analysis, thermogravimetric analysis (TGA), molar conductivity measurements and spectral studies ((1)H NMR, FT-IR, UV-vis, and luminescence). The Schiff base ligand coordinates to Ln(III) ion in a tetra-dentate manner through the phenolic oxygen and azomethine nitrogen atoms. The coordination number of eight is achieved by involving two bi-dentate nitrate groups in the coordination sphere. Sm, Tb and Dy complexes exhibit the characteristic luminescence emissions of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of the complexes exhibit antibacterial activity against a number of pathogenic bacteria.     

Investigation of properties of rare earth complexes with dibromo- p -methyl-methylsulfonazo by spectral correction technique

The reactions were sensitive between seven rare earth (RE) metals Nd(III), La(III), Ce(III), Pr(III), Sm(III), Eu(III) and Gd(III) and dibromo-p-methylmethylsulfonazo (DBMMSA) in acidic solution. The spectral correction method has been applied in the determination of properties of RE complexes instead of ordinary spectrophotometry. Composition ratios, real molar absorptivities (ε) and stepwise stability constants (K) of each of the RE complexes were determined easily because the method eliminated the absorption influence of excess of ligand on complex. Results showed that the cumulativeK values of the complexes were between 3.91 × 10¹⁴ and 2.34 × 10²⁸ and the real (not apparent) absorptivity between 8.85 × 10⁴ and 2.12 × 10⁵ l mol^-1cm^-1 at 640 nm.     

In vitro antimicrobial and antioxidant evaluation of rare earth metal Schiff base complexes derived from threonine

Six novel Ln(III) Schiff base complexes were synthesized using rare earth metals with threonine and 5‐bromosalicylaldehyde, namely Pr(III), Sm(III), Gd(III), Tb(III), Er(III) and Yb(III) Schiff bases. These complexes were characterized using elemental analysis, molar conductivity, Fourier transform infrared and UV–visible spectroscopies, and thermogravimetry–differential thermal analysis. The general formula of the complexes is [Ln(L)(NO₃)₂(H₂O)].NO₃ (L = Schiff base ligand). The spectroscopic data reveal that the Schiff base ligand behaves as a tridentate ligand with ONO donor atoms sequencing towards the central metal ion. An investigation of fluorescence properties of the Sm(III), Er(III) and Tb(III) complexes shows that the Ln(III) ions can be sensitized efficiently by the ligand to some extent. Antimicrobial activity testing indicates that all six complexes exhibit antibacterial and antifungal ability against microbes with broad antimicrobial spectra. In addition, the antioxidant properties of the complexes were also screened. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermal investigation and infrared evolved gas analysis of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid

The characterisation of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid of the formula Ln₂pdc₃·nH₂O where Ln denotes lanthanides from La to Gd, pdc = C₇H₅NO₄²⁻; n = 6 for Ce(III), n = 7 for Pr(III) and Sm(III), n = 8 for La and n = 13 for Nd(III), Eu(III) and Gd(III) was performed by the thermal analysis TG-DTA and the simultaneous infrared evolved gas analysis TG-FTIR. Heating of the crystalline complexes resulted in the dehydration process at first. Next, dehydrated compounds decompose releasing of CO₂, CO, CH₄ and hydrocarbons. Free pyridine molecules were detected only in the gaseous products of lanthanum(III) complex decomposition.