The extraction of Yb(III) and Lu(III) with chloroform from aqueous solutions in the presence of cupferron

The equilibrium of distribution of Yb(III) and Lu(III) between chloroform and the aqueous phase in the presence of cupferron (the ammonium salt of N-nitrosophenylhydroxylamine) were studied as apH function of the aqueous phase and the concentration of N-nitrosophenylhydroxylamine (HL). The stability constants for theLnL _n ^3–n ) complexes (n=1÷3) being formed in the aqueous phase were established, as well as the equilibrium constants of the extraction reaction $$Ln(H_2 O)_m^{3 + } + 3HL_{(O)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(O)} + 3H^ + + mH_2 O(Ln^{3 + } = Yb,Lu),$$ two-phase stability constants for theLnL ₃ complexes,pH _0.5 and the separation factor Lu(III) from Yb(III).     

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”.     

Effect of p-tert-butylcalix[4]arene fitted with phosphinoyl pendant arms as synergistic agent in the solvent extraction of trivalent lanthanoids with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione and structural study of solid complexes by IR,NMR and X-ray

The synergistic solvent extraction of five selected lanthanoid ions (La³⁺, Nd³⁺, Eu³⁺, Ho³⁺ and Lu³⁺) with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HL) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(dimethylphosphinoylmethoxy)calix[4]arene, (S) in CHCl₃ has been studied. It was found that in presence of this phosphorus-containing calix[4]arene the lanthanoid ions have been extracted as [LnL₃S₂]. The values of the equilibrium constants and the separation factor have been calculated. The influence of the synergistic agent on the extraction process has been discussed.     

Influence of complexing species on the extraction of trivalent actinides from lanthanides with CyMe<Subscript>4</Subscript>–BTBP: a theoretical study

We studied geometric and electronic structures as well as thermodynamic properties of complexes [M(CyMe₄–BTBP)₂(NO₃)]²⁺ and [M(CyMe₄–BTBP)₂]³⁺ with M?=?Am(III), Cm(III) and Ln(III) (La–Lu) theoretically. The actinide–nitrogen bonding is principally ionic with higher covalency in An–N bonds than in the Ln–N analogues. The selectivity towards An(III) over Ln(III) (La, Ce, Pr, Pm, Sm, Eu and Yb) is influenced by formed complexes to different extents by comparison of changes of Gibbs free energy of reaction, ΔΔG_Am/Ln, for formation of [AmL₂]³⁺/[LnL₂]³⁺, [AmL₂(NO₃)]²⁺/[LnL₂(NO₃)]²⁺, and [AmL₂(NO₃)]²⁺/[LnL₂]³⁺. The Am(III) selectivity is enhanced for [AmL₂(NO₃)]²⁺/[LnL₂]³⁺ over [AmL₂]³⁺/[LnL₂]³⁺.     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

Extraction of lutetium(III) and erbium(III) with 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous solutions was examined. The composition of the complex extracted was determined and it was found that the extraction process can be described by the following equation (Ln ³⁺=Lu, Er): $$Ln(H_2 O)_m^{3 + } + 3 HL_{(0)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(0)} + 3 H^ + + mH_2 O$$ The extraction constants (K _ex ) and two-phase stability constants (β ₃ ^x ) forLnL ₃ complexes have been evaluated.     

Lanthanide-Ion Complexation by D-Glucuronic and D-Galacturonic Acids

To assess the potential of naturally occurring substances in the treatment of heavy-metal intoxication, the interaction between D -galacturonic and D -glucuronic acids with several trivalent lanthanide ions has been studied in aqueous solutions by means of a spectrophotometric method (27°; 0.1M NaClO₄; pH 4.0). Values for the overall stability constants for [LnL] and [LnL₂] (Ln = La, Ce, Pr, Nd, Gd, or Lu) complexes are presented and discussed. The interpretation of the data shows that, similarly to acetates, the COOH group coordinates metal ions in both [LnL] and [LnL₂] complexes. The 1:1 complexation is supplemented by the ring C(5)? O-atom. Moreover, the C(4)? O-atom seems to play an important role in the steric hindrance of the chelating ligand molecules.     

Effect of ionic strength on the stabilities of ciprofloxacin – Metal complexes

Proton–ligand dissociation constant of 1-cyclopropyl-1,4-dihydro-4-oxo-7-(1-piperazinyl) quinolone-3-carboxylic acid is ciprofloxacin and metal–ligand stability constants of its complexes with some metal ions have been determined potentiometrically in the presence of (0.01, 0.02 and 0.03 mol/dm³) NaClO₄. The order of the stability constants of the formed complexes increases in the sequence Cu²⁺, Fe³⁺, Ni²⁺ and Zn²⁺ and decreases with increase in the concentration of ionic strength.     

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.     

Different Complexation of Nd3+ and Sm3+ with L-Malic Acid

Complexation of Nd³⁺ and Sm³⁺ ions with L-malic acid (H₃Mal) in aqueous solutions (I = 0.1 mol/l KCl) was studied by pH-metric titration at the molar concentration ratios of H₃Mal : lanthanide equal to 1 : 2, 1 : 1, 2 : 1 in the pH range 2.8–9.5. Mathematical modeling of composite equilibrium processes was used to determine the compositions and stability constants of Nd(III) and Sm(III) L-malate complexes. It was found that in addition to the 1 : 1 and 1 : 2 complexes with different degree of deprotonation, the protonated L-malate complexes and hydroxo complexes of these metals were also formed. The Sm³⁺ and Nd³⁺ ions were established to behave differently during complexation with H₃Mal.     

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.     

Formation and Stability of Binary Complexes of Divalent Ecotoxic Ions (Ni, Cu, Zn, Cd, Pb) with Biodegradable Aminopolycarboxylate Chelants (dl-2-(2-Carboxymethyl)Nitrilotriacetic Acid, GLDA, and 3-Hydroxy-2,2′-Iminodisuccinic Acid, HIDS) in Aqueous Solutions

The protonation and complex formation equilibria of two biodegradable aminopolycarboxylate chelants {dl-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2??-iminodisuccinic acid (HIDS)} with Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions were investigated using the potentiometric method at a constant ionic strength of I?=?0.10?mol·dm^?3 (KCl) in aqueous solutions at 25?±?0.1?°C. The stability constants of the proton?Cchelant and metal?Cchelant species for each metal ion were determined, and the concentration distributions of various complex species in solution were evaluated for each ion. The stability constants (log₁₀ K _ML) of the complexes containing Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions followed the identical order of log₁₀ K _CuL?>?log₁₀ K _NiL?>?log₁₀ K _PbL?>?log₁₀ K _ZnL?>?log₁₀ K _CdL for either GLDA (13.03?>?12.74?>?11.60?>?11.52?>?10.31) or HIDS (12.63?>?11.30?>?10.21?>?9.76?>?7.58). In each case, the constants obtained for metal?CGLDA complexes were larger than the corresponding constants for metal?CHIDS complexes. The conditional stability constants (log₁₀ $ K_{\text{ML}}^{'} $ ) of the metal?Cchelant complexes containing GLDA and HIDS were calculated in terms of pH, and compared with the stability constants for EDTA and other biodegradable chelants.     

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (La3+, Nd3+, Sm3+, Gd3+)

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H₂L), a Trichoderma secondary metabolite, of a selection of tripositive rare-earth cations Ln³⁺ (Ln³⁺ = La³⁺, Nd³⁺, Sm^3+, and Gd³⁺) was investigated at 25 °C, and in a CH₃OH/0.1 M NaClO₄ (50/50 w/w) solvent, using mass spectrometry, circular dichroism, UV–Vis spectrophotometry, and pH measurements. Experimental data can be satisfactorily explained by assuming, for all investigated cations, the formation of a mono-complex (LnL⁺) and a bis-complex (LnL₂⁻). Differences were found between the formation constants of complexes of different Ln³⁺ cations, which can be correlated with ionic radius. Since gadolinium is the element that raises the most concern among lanthanide elements, its effects on organisms at different levels of biological organization were explored, in the presence and absence of harzianic acid. Results of ecotoxicological tests suggest that harzianic acid can decrease gadolinium biotoxicity, presumably because of complex formation with Gd³⁺.     

Metal Complexes of Pentadentate Macrocyclic Ligands Containing Oxygen and Nitrogen as Donor Atoms

Four macrocyclic ligands have been synthesized: 1-oxa-4,7,10,13-tetraazacyclopentadecane ( 1 ), 1,4-dioxa-7,10,13-triazacyclopentadecane ( 2 ), 1,4-dioxa-7,11,14-triazacyclohexadecane ( 3 ), 1,4-dioxa-7,11,15-triazacycloheptadecane ( 4 ), one of them 3 , for the first time. The protonation constants of the ligands and the stability constants of the complexes formed by the four ligands with some divalent first-series transition-metal ions, Cd²⁺ and Pb²⁺, were determined by potentiometric methods, in aqueous solution, at 25° and I = 0.10M (KNO₃). The sequence of protonation of ligand 1 was studied by ¹H-NMR spectroscopy. The Irving-Williams' order of stability is obeyed for the complexes of all the ligands, and the metal complexes of 1 present the higher values of stability. A drop in the stability of all the metal complexes studied is observed when the metal complexes of 1 are compared with the corresponding complexes of 2 . The effect of the increase of the ring size of the macrocycle can be observed for metal complexes of the series of ligands 2 4 , where, in spite of the slight increase of the overall basicity of the ligands (20.28, 22.25, and 24.96 for 2, 3 , and 4 respectively), small differences in stability are found for the corresponding complexes of 2 and 3 , but a significant drop occurs for all the metal complexes formed with the 17-membered ligand, specially for the larger metal ions like Mn²⁺ and Pb²⁺.     

Potentiometric and Conductometric Studies on the Complexes of Some Rare Earth Metals with Rhodanine Azosulfonamide Derivatives, XII

Stability constants for La³⁺, Ce³⁺, UO₂ ²⁺, and Th⁴⁺ metal ion complexes with rhodanine azosulfonamide derivatives have been determined potentiometrically in 0.1 M KCl in a 30% (v/v) ethanol–water mixture. The order of the stability constants of the complexes found was to La³⁺ < Ce ²⁺ < UO ₂ ²⁺ < Th ⁴⁺. The influence of substituents on the stability of the complexes was examined on the basis of electron-repelling property of the substituent. The effect of temperature on the stability constants was studied and the Gibbs energy, the enthalpy, and entropy of complexation thermodynamic parameters were derived and are discussed. The stoichiometries of these complexes were determined conductometrically and the results indicated the formation of 1:1 and 1:2 (metal:ligand) complexes.     

Potentiometric and thermodynamic studies of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)-sulfamoyl]phenylazo}-2-pyrazolin-5-one and its metal complexes

The dissociation constants of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)sulfamoyl]phenylazo}-2-pyrazolin-5-one and metal-ligand stability constants of its complexes with some transition metal ions have been determined potentiometrically in 0.1 M-KCl and ethanol—water mixture (30 vol. %). The order of the stability constants of the formed complexes increases in the sequence Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, La³⁺, Hf³⁺, UO ₂ ²⁺ , Zr⁴⁺. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes was found to be spontaneous, exothermic, and entropically favourable. Abstracted from his M.Sc. Thesis.     

Study of acidic and complexing properties of tetraphenylporphyrazine and octa(4-bromophenyl)porphyrazine in DMSO at 298 K

The acid dissociation of tetraphenylporphyrazine (H₂PA(Ph)₄) and octa(4-bromophenyl)porphyrazine (H₂PA(4-BrPh)₈) and their reactions with Cd²⁺ ions were studied in DMSO at 298 K. The equilibrium formation constants of the complexes and the acid dissociation constants of porphyrins were calculated; their relationship with the stability constants of the complexes was analyzed. The acidity sequence for porphyrazine derivatives was established.     

The effect of ligand donor atoms on ternary complex stability

Formation constants of mixed ligand complexes of Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Mn²⁺,with cyadine-5′-monophosphoric acid (CMP) and various primary ligands such as 1,10-phenanthroline(phen), glycylglycine(glygly) and salicylic acid (sal) have been determined in aqueous solution at 35°C and 0.1 M (KNO₃) by potentiomeric measurements. The acid dissociation constants of all the above mentioned ligands together with their 1 : 1 binary metal complex formation constants were also measured at 35°C. In general all the 1 : 1 binary complexes follow the Irving-Williams order of stability. Further the binary metal complexes of primary ligands are more stable than their ternary complexes with CMP. For ternary complexes, Δ(log K) values seem to change from positive to highly negative as the coordinating atoms of the primary ligands were varied from N,N to N,O^? to O^?O^?. The higher stability of ternary complexes involving phen is due to its Π-bonding interaction with the above metal ions and the relative decrease in the stability of other ternary systems is due to the coulombic repulsion of donor oxygen atoms of primary and secondary ligands. Thus for ternary complexes the stabilities follow a decreasing order of M-phen-CMP > M-glygly-CMP > M-sal-CMP.     

H NMR study of interparticle interactions in the system rare-earth element-acetic acid-diamagnetic salt

Complexation of acetic acid in 5.0 M NaNO₃ at 298 K with yttrium-group rare-earth ions (Dy³⁺, Er³⁺, Tm³⁺, Yb³⁺) in the absence and in the presence of Mg²⁺ ions was studied by ¹H NMR spectroscopy in combination with mathematical simulation of complex equilibria. In the presence of Mg²⁺, the stability constants of monoacetate complexes of rare-earth ions decrease relative to the Mg-free systems.     

Solvent extraction of lanthanide ions with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP)

The solvent extraction of Er(III), Yb(III) and Lu(III) by 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP or HL) in carbon tetrachloride has been studied as a function of thepH of the aqueous phase and the concentration of the extractant in the organic phase. The equation for the extraction reaction has been suggested as: $$Ln^{3 + } + 3HL_{(0)} \rightleftharpoons LnL_{3(0)} + 3H^ + \left( {Ln^{3 + } = Er,Yb, Lu} \right)$$ The extraction equilibrium constants (K _ex ) and two-phase stability constants (β ₃ ^x ) for theLnL ₃ complexes have been evaluated.     

Thermodynamische Untersuchungen zur Chelatbildung zwischen Aminoterephthalsäure-N,N-diessigsäure und 3 d- bzw. Erdalkalimetallionen. Eine Betrachtung zum Einfluß einer koordinativ inaktiven Carboxylgruppe auf die komplexe Bindung von Metallionen durch Aminopolycarbonsäuren

N-(2-Carboxyphenyl)iminodiacetic acid (H₃A) and N-(2,5-dicarboxyphenyl)iminodiacetic acid (H₄B) are tetradentate ligands and form complexes of the composition MA- and MB^2? with M^II ions. These compounds differ by the additional charge of the second carboxylic group only, which is fixed to the benzene nucleus and which is unable for coordination for steric reasons. Using an anisothermal calorimeter ΔH values for the formation of the complexes MA- and MB^2? in aqueous solution have been measured at an ionic strength 0.1 m KNO₃. From these data, and from the stability constants of the complexes, entropy changes ΔS have been calculated. In all cases investigated (M^m+ = H⁺, Mg²⁺, Ca²⁺, Sr²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) the ΔH values are more negative for the complexes MA^m-3 than for complexes MB^m-4, whereas the ΔS values are greater for complexes MB^m-4. Using a simple model for the molecules of the complexes MB^m-4 and empirically determined dielectric constants of the medium between the central ions and the noncoordinated ionized carboxylic group, the electrostatic attraction between these charges was calculated. Basing on these results the influence of the noncoordinated carboxylic group on the central atom by the mesomeric and inductive effect is discussed.