A thermodynamic study of complexation reaction of yttrium(III), lanthanum(III) and cerium(III) with tyrosine

The thermodynamic stability constants and thermodynamic parameters for complexation reaction of Y³⁺, La³⁺, and Ce³⁺ with tyrosine have been determined pH metrically. The study reveals the formation of 11 complexes for La³⁺ and Ce³⁺ whereas Y³⁺ yields both 11 and 12 complexes. The values of enthalpy changes (H ^o) indicate that unionised hydroxy group also participates in complexation.     

Thermodynamic study of extraction of cerium(III) and yttrium(III) with tributyl phosphate

To increase the efficiency of hydrometallurgical processing of lean rare-earth raw material, the effect of salt anion and metal cation on the characteristics of Ce(III) and Y(III) recovery from dilute aqueous solutions with tri-n-butyl phosphate was studied on the basis of the thermodynamic theory of extraction.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1430–1434.Original Russian Text Copyright © 2004 by Chirkst, Litvinova, Chistyakov, Ionova.     

Formation constants of chromium(III), scandium(III) and yttrium(III) complexes of some hydroxy naphthoic acids

The complexes of chromium(III), scandium(III) and yttrium(III) formed by 1-hydroxy-2-naphthoic acid (1,2-HNA: H2L) and 3-hydroxy-2-naphthoic acid (3,2-HNA: H2L) were investigated by potentiometry and spectroscopy at 25+/-0.1 degrees C and at an ionic strength of 0.1 M KNO3 in 50% ethanol-water (v/v) medium. The stoichiometries of these three M(III) complexes formed with these hydroxy-naphthoic acids and with hydroxo ion were defined and their formation constants were determined and compared. Thus, the removing capacities of these ligands could be examined by calculating the equilibrium concentration of Cr(III) that exists in the discharge water of various industries since Cr(III) ions are the main pollutants present during waste water treatment in our city, Bursa.     

Thermodynamics of cerium(III) extraction with naphthenic acids

Cerium(III) extraction from dilute aqueous solutions with naphthenic acids in decane was studied. The dependence of the distribution ratio on the pH of the equilibrium aqueous phase was determined, and the extraction equilibrium constant and Gibbs energy were calculated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1630–1633.Original Russian Text Copyright © 2004 by Chirkst, Litvinova, Devyatkin, Zhadovskii.     

Complexation,solubilities and thermodynamic functions for cerium(III) fluoride-water system

The solubility, solubility product and the thermodynamic functions for the CeF₃–H₂O system have been measured using the radiometric, conductometric and potentiometric techniques. The radiometric values for the solubility and solubility product, the lowest and more acceptable for reasons cited in previous papers, are 3.14·10^–5 M and 2.17·10^–17 respectively. The enthalpy change measured by the conductometric method is almost twice as that obtained by potentiometric method due to abnormal conductances registered at higher temperatures. The average values for H^o and G^o and S^o at 298 K are 53.0±17.4, 91.7±4.0 and –129.7±58.2 KJ·mol^–1 respectively. The positive values for H^o and G^o and the negative value for S^o are indicative of the low solubility of this salt in water. The stability constants for the mono- and difluoride complexes of Ce(III) have been determined potentiometrically using unsaturated solution mixtures of Ce(III) and F^–. These values for CeF⁺ and CeF ₂ ⁺ are 997±98 and (1.03±0.44)·10⁵, respectively. Studies on pH dependence of the solubility shows that the solubility reaches a minimum value at a pH of about 3.2.     

A conductometric study of complexation reaction between dibenzo-24-crown-8 with yttrium cation in some binary mixed non-aqueous solvents

The complexation reaction of macrocyclic ligand, dibenzo-24-crown-8 (DB24C8) with Y⁺³ cation was studied in some binary mixtures of methanol (MeOH), ethanol (EtOH), acetonitrile (AN) and tetrahydrofuran (THF) with dimethylformamide (DMF) at different temperatures using the conductometric method. The conductance data show that in all solvent systems, the stoichiometry of the complex formed between DB24C8 and Y⁺³ cation is 1:1 (ML). The stability order of (DB24C8.Y)⁺³ complex in pure non-aqueous solvents was found to be: AN > EtOH > MeOH > DMF. A non-linear behaviour was observed for changes of log K_f of (DB24C8.Y)⁺³ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the heteroselective solvation of the species involved in the complexation reaction. The obtained results show that the stability of (DB24C8.Y)⁺³ complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (?H°_c and ?S°_c) for formation of (DB24C8.Y)⁺³ complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the (DB24C8.Y)⁺³ complex is enthalpy destabilized but entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.     

Spatial structure and thermodynamic aspects of Dy(III) complex formation with some mono- and dicarboxylic acids

Spatial structures of complexes [DyAc]²⁺, [DyBz]²⁺, [DyAc₂]⁺ and [DyBz₂]⁺ in aqueous solutions (Ac^– and Bz^–, acetate and benzoate anions, respectively) are studied using the paramagnetic double refraction method. The polyhedra of [DyAc(H₂O)₆]²⁺ and [DyBz(H₂O)₆]²⁺ are dodecahedra with ligands coordinated at one of the edges. In the complexes [DyAc₂(H₂O)₄]⁺ and [DyBz₂(H₂O)₄]⁺ the ligands are coordinated at the edges of a square antiprism at an angle of 50 (55)° to the local symmetry axis of higher symmetry.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1038–1040, June, 1993.     

A thermodynamic study of the complexation reaction of beryllium(II), magnesium(II) and calcium(II) with 3-hydroxy-2-naphtoic acid

The thermodynamic stability constants and thermodynamic parameters for the complexation reaction of Be²⁺, Mg²⁺ and Ca²⁺ with 3-hydroxy-2-naphthoic acid have been determined pH metrically in a 70% v/v dioxane-water medium in the presence of potassium nitrate. The study showed the formation 1:1 and 1:2 complexes of Be²⁺, Mg²⁺ and 1:1 complex of Ca²⁺ with 3-hydroxy-2-naphthoic acid. The order of overall stability is Be²⁺>Mg²⁺>Ca²⁺.     

Rate constants for the reaction of OH radicals with some amino polycarboxylic acids

Rate constants of OH radical reaction with some amino polycarboxylic acids (APCAs) such as EDTA, DTPA, HEDTA, NTA, and HIDA have been determined at different pHs using pulse radiolysis competition kinetics method with thiocyanate as the reference solute. The rate constants varied with pH (possibly due to their various pKs) and the plots of rate constants vs. pH are given. Rate constants for OH radical reaction with the various acid–base forms of these amino polycarboxylic acids are estimated from the plateau values in the plots. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 99–104, 2000     

Properties of fluoroantimonates(III) complexes with amino acids

Crystalline complex fluoroantimonates(III) with amino acids (glycine, β-alanine, DL-serine, DL-valine, L-leucine, and L-phenylalanine) have been prepared. The complexes stability in aqueous solutions has been studied with the cementation method. ¹H NMR studies of aqueous solutions of the amino acids complexes with SbF₃ at pH 1–6 and room temperature are reported. Preparation of polycrystalline metal antimony in aqueous solutions of tetrafluoroantimonates(III) complexes with the protonated amino acids has been demonstrated.     

Solvent extraction of lanthanum(III) and cerium(III) with dialkyldithiophosphoric acids. Separation from thorium(IV)

The extraction of lanthanum(III) and cerium(III) with dialkyldithiophosphoric acids, Hdtp, into different polar and nonpolar solvents (cyclohexane, benzene, carbon tetrachloride, chloroform, diethyl ether, dibutyl ether, n-butanol and cyclohexanone) from aqueous solutions containing perchlorate, nitrate and chloride anions has been investigated. The effect of various factors, such as nature of the solvent, pH, metal concentration and foreign anions present in the aqueous phase was investigated in order to establish the mechanism of extraction process. The data obtained suggest an ion-exchange mechanism. The anions present in the aqueous phase do not participate in the extraction process and do not influence significantly the magnitude of the extraction ratios either. The extracted species in the organic phase is a 12 complex of lanthanide with Hdtp. The extraction efficiency (E%) is calculated and the possibility of Th-rare earths separation is discussed.     

The luminescence system of yttrium(III)-BPMPHD-CTMAB and the determination of yttrium(III)

The study indicated that yttrium(III) could form an ion association compound with a new synthetic reagent, 1,6-bi(1′-phenyl-3′-methyl-5′-pyrazolone-4′-)hexanedione (BPMPHD) and cetyl trimethyl ammonium bromide (CTMAB). The compound could enhance the natural fluorescence of BPMPHD by about 260 times, upon which a new fluorescence method was developed for determining yttrium in rare earth (RE) samples. The determination range was 9–900 ng/ml. The detection limit was 1.8 ng/ml. The composition of the ion association was [Y(BPMHD)₂]⁻CTMAB⁺.     

Theoretical computation of interaction parameters for the complexation of GSH with Pr(III) and Mg(II) in solution: Analysis of their reaction dynamics and thermodynamic characters

The current research focuses on the computation of absorption spectral parameters like energy interaction parameters viz. Slater-Condon factor (F_k), Racah (E^k), Lande spin-orbit interaction (ζ_4f), nephelauxetic ratio (β), bonding parameter (b^1/2), per cent covalency (δ), and the intensity parameters like oscillator strength (P) and Judd-Ofelt T_λ, (λ ​= ​2,4,6) parameters, of Pr³⁺ ion complexes with reduced Glutathione (GSH) in the presence and absence of Mg²⁺ in different aqueous solutions of CH₃OH, C₄H₈O₂, CH₃CN and DMF. The variations in the values of the energy interaction and intensity parameters clearly demonstrates the relative sensitivity of the 4f-4f transitions and its correlation with ligand structure and the nature of metal-ligand interaction. Further, the reaction dynamics and thermodynamic properties for the complexation of Pr³⁺ with glutathione and Mg²⁺ ligand have been investigated using different computed parameters like rate constant (k), activation energy (E_a), A (pre-exponential factor) and thermodynamic parameters, ΔH⁰, ΔG⁰ and ΔS⁰.     

A comparative study of the complexation of Am(III) and Eu(III) with TODGA in room temperature ionic liquid

On the growing awareness of the environmental impact associated with the use of volatile organic diluents, room temperature ionic liquid gained world-wild acceptance as environmentally benign diluents for actinide partitioning. The observed unusual behavior of less extraction efficiency of Eu with TODGA in RTIL in comparison with that of Am-TODGA was addressed in this paper. The stoichiometry of Am-TODGA complex was found to be 1:2 while that of Eu-TODGA was 1:1. More the ligand molecules associated in the metal ligand complex, the organophilicity of the complex will be more and the solubility of the metal–ligand complex in RTIL will be more which reflects in the higher distribution ratio for Am. In RTIL both Am and Eu showed slower kinetics of extraction with TODGA which can be attributed to the high viscosity coefficient of RTIL compared to the molecular diluents. The observed slower kinetics of extraction was quantified and found to follow first order kinetics with the rate constant of 5.5 × 10^?4 s^?1. The formation constant of Am-TODGA complex was found to be more (4.18 × 10⁸ M^?1) than Eu-TODGA complex (3.31 × 10⁸ M^?1) in RTIL. The parameters viz. diffusion coefficient, activation energy for Eu(III)/Eu(II) were determined and found to be 3.08 × 10^?8/cm² s^?1 (at 303 K) and 39.34 kJ mol^?1 respectively. The thermodynamic parameters ΔG, ΔH and ΔS for the reaction were evaluated using the linear regression of the plot of E ^0* versus T. The redox reaction was found to be exothermic with decrease in entropy value.     

Potentiometric and spectroscopic studies on yttrium(III) complexes of dihydroxybenzoic acids

The equilibrium reactions of yttrium(III) ion with dihydroxybenzoic acids (2,3-dihydroxybenzoic acid (2,3-DHBA) and 3,4-dihydroxybenzoic acid (3,4-DHBA)) (H(3)L) were investigated in aqueous solution by means of potentiometric and spectroscopic methods, in 0.1 mol.l(-1) ionic strength medium at 25 degrees C. The stability constants are reported for YL, YL(HL)(2-) and YL(2)(3-)- type mononuclear complexes. 2,3-DHBA can bind Y(III) ion strongly and the salicylate mode is effective over the acidic pH range. But in higher pH range, 2,3-DHBA and 3,4-DHBA act more efficiently through catecholate groups. The complexes of 2,3-DHBA are more stable than the complexes of 3,4-DHBA.     

Complex formation equilibria between aluminum(III), gadolinium(III) and yttrium(III) ions and some fluoroquinolone ligands. Potentiometric and spectroscopic study

Complex formation equilibria of aluminum(III), gadolinium(III), and yttrium(III) ions with the fluoroquinolone antibacterials moxifloxacin, ofloxacin, fleroxacin, lomefloxacin, levofloxacin, and ciprofloxacin were studied in aqueous solution by potentiometric and spectroscopic methods. The identity and stability of metal–fluoroquinolone complexes were determined by analyzing potentiometric titration curves (310 K, μ = 0.15 M NaCl, pH range = 2–11, C_L/C_M = 1?:?1 to 3?:?1, C_M = 1.0 mM) with the aid of Hyperquad2006 program. The main species formed in the system may be formulated as M_pH_qL_r (p = 1, q = ?2 to 2, r = 1–3, L = fluoroquinolone anion, logarithm of overall stability constant, log β_p,q,r = in the range ca. ?10 to 45). The stability of complexes is mostly influenced by metal ion properties (ionization potential, ionic radius) indicating partial ionic character of the coordination bond. The complexes were also characterized by spectroscopic measurements: spectrofluorimetry, ¹H-NMR, and ESI-MS. Fluorimetric data were evaluated with the aid of HypSpec2014 and indicated the formation of ML_r (r = 1–3) complexes with cumulative conditional stability constants significantly lower than the thermodynamic ones. NMR and MS data corroborate potentiometrically determined speciation. Calculated plasma mobilizing capacity of the ligands generally follows the order levofloxacin > moxifloxacin > ciprofloxacin at concentration levels of the ligands higher or equal to ca. 10^?4 M.