Stability Constants of Chloride Complexes of Lanthanum

Fernández-Ramírez,†,‡, Edelmira; Jiménez-Reyes, † and Melania; Solache‐Ríos, M.

doi:10.1021/je060290k

Cited by 6 publications

(20 citation statements)

References 17 publications

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“…From the coordination number histogram of Cl – anions hydrating the La 3+ cations and, consequently, knowing the concentrations of the various species in the solution, it is possible to estimate the stability constants for the various ion complexes. For example, for the equilibrium between a solvated anion and solvated cation with the corresponding ion-paired complex, we can write L a ( a q ) 3 + + C l ( a q ) − ⇌ L a C l ( a q ) 2 + and calculate β L a , C l = [ L a C l 2 + ] [ L a 3 + ] [ C l − ] Using the percentages shown in the lower panel of Figure , we obtain a value of ≈1.4 ± 0.1 mol –1 dm –3 which is a reasonable estimate when compared to the range of values found in the literature (0.67–1.6 mol –1 dm –3 ) for lanthanum chloride solutions of ionic strengths in the range from 1 to 4 mol dm –3 …”

Section: Resultsmentioning

confidence: 99%

“…Using the percentages shown in the lower panel of Figure 5, we obtain a value of ≈1.4 ( 0.1 mol À1 dm À3 which is a reasonable estimate when compared to the range of values found in the literature (0.67À1.6 mol À1 dm À3 ) for lanthanum chloride solutions of ionic strengths in the range from 1 to 4 mol dm À3 . 30 To complete the picture of the ion interactions in the 1 m LaCl 3 solution, Figure 6 shows the ClÀO water and ClÀH water pair distribution functions and running coordination numbers. As expected for the chloride ions, the average hydration number for these ions is approximately six, although a little less since a significant number of these anions are, as previously seen, directly ion paired with the La 3þ cations.…”

Section: ' Results and Discussionmentioning

confidence: 99%

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Solvation Structure and Ion Complexation of La³⁺ in a 1 Molal Aqueous Solution of Lanthanum Chloride

2011

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H/D isotopic substitution neutron scattering and X-ray scattering have been used to investigate the short and intermediate range solution structure in a 1 m aqueous solution of lanthanum chloride. To improve the reliability of the local structural information on the cation environment, information has been incorporated from Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy data into the applied analytical framework. The markedly different structural sensitivities of the experimental probes allow the construction of a detailed three-dimensional atomistic model using the Empirical Potential Structure Refinement (EPSR) technique. The results show that at the investigated concentration La(3+) is hydrated by eight water molecules and one chloride ion, forming an inner-sphere ion complex in which the water molecules maintain angular configurations consistent with a tricapped trigonal prism configuration. This local geometry considerably disrupts the bulk solvent structure.

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Section: Resultsmentioning

confidence: 99%

Section: ' Results and Discussionmentioning

confidence: 99%

Solvation Structure and Ion Complexation of La³⁺ in a 1 Molal Aqueous Solution of Lanthanum Chloride

2011

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“…From equilibrium constants measured using different techniques and under different conditions (ionic strengths between 1 and 4 M, β La,Cl = 0.67 to 1.6 mol dm –3 ), , free energies between Δ G = −0.3 to +0.2 kcal/mol can been derived for this reaction. Extrapolation to zero ionic strength has afforded an estimate of log β 0 La,Cl = 1.43 (±0.12) mol dm –3 , corresponding to Δ G 0 = 2.0 kcal/mol. Despite the shortcomings of our DFT level discussed above, the CPMD-derived Δ A in eq is in excellent agreement with this value, apparently benefiting from fortuitous error cancellation.…”

Section: Resultsmentioning

confidence: 99%

Speciation of La(III) Chloride Complexes in Water and Acetonitrile: A Density Functional Study

et al. 2012

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Car-Parrinello molecular dynamics (CMPD) simulations and static computations are reported at the BLYP level of density functional theory (DFT) for mixed [LaCl(x)(H(2)O)(y)(MeCN)(z)](3-x) complexes in aqueous and nonaqueous solution (acetonitrile). Both methodologies predict coordination numbers (i.e., x + y + z) that are successively lower than nine as the Cl content increases from x = 0 to 3. While the static DFT method with implicit solvation through a polarizable continuum model overestimates the binding strength of chloride and erroneously predicts [LaCl(2)(H(2)O)(5)](+) as global free-energy minimum, constrained CPMD simulations with explicit solvent and thermodynamic integration reproduce the weak binding of chloride in water reasonably well. Special attention is called to the dipole moments of coordinated water molecules as function of coligands and solvent, evaluated through maximally localized Wannier function centers along the CPMD trajectories. Cooperative polarization of these water ligands by the metal cation and the surrounding solvent is remarkably sensitive to fluctuations of the La-O distances and, to a lesser extent, on the La-water tilt angles. The mean dipole moment of water ligands is rather insensitive to the other coligands, oscillating around 3.2 D, 3.5 D, and 3.3 D in MeCN, water, and [dmim]Cl solution, respectively, the latter being an archetypical ionic liquid.

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“…A recent study employed solvent extraction methods to determine stability constants in Er chloride solutions with ionic strengths varying from infinite dilution through 4 mol/dm 3 . Equilibria were established in aqueous solution, and then the free, uncomplexed Er was extracted into n -heptane using dinonylnapthalene sulfonic acid following an earlier discussed procedure . These extractions were carried out as a function of chloride concentration in the aqueous phase, and after extraction into the organic phase the Er concentration was quantified with visible spectrophotometry.…”

Section: Discussionmentioning

confidence: 99%

“…Equilibria were established in aqueous solution, and then the free, uncomplexed Er was extracted into n-heptane using dinonylnapthalene sulfonic acid 21 following an earlier discussed procedure. 34 These extractions were carried out as a function of chloride concentration in the aqueous phase, and after extraction into the organic phase the Er concentration was quantified with visible spectrophotometry. For solutions with ionic strengths g1 the authors compared fits to their extraction results using linear and second-order polynomial fitting, from which they concluded that the errors in the latter were generally slightly higher.…”

Section: Discussionmentioning

confidence: 99%

Structures and Energetics of Erbium Chloride Complexes in Aqueous Solution

2009

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A series of aqueous, constant ionic strength solutions containing 0.5 m Er is studied as a function of chloride/perchlorate ion concentration using high-energy X-ray scattering (HEXS) to probe the metal ion coordination environment. Perchlorate is seen to form an outer-sphere complex only in the end member (4.0 m perchlorate) of the series. Chloride ions are seen to bind as both inner- and outer-sphere complexes. A quantitative analysis of the scattering data is used to determine stability constants that depend on whether the complexation with chloride ions is assumed to add to or to replace the waters bound in the first coordination sphere. Published stability constants obtained from liquid-liquid extraction clarify the mechanism involved and, together with the HEXS data, present a consistent picture of the chemistry. The stability constants determined from the HEXS data, beta(1) = 0.38(8) and beta(2) = 0.014(9), are small, less than the available thermal energy in solution at room temperature. The combination of chemical separations and HEXS data for the analysis supports the argument that the complexes formed are real under the experimental conditions. Details of the structural correlations and interactions are discussed for applications including separations and environmental modeling.

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Stability Constants of Chloride Complexes of Lanthanum

Cited by 6 publications

References 17 publications

Solvation Structure and Ion Complexation of La³⁺ in a 1 Molal Aqueous Solution of Lanthanum Chloride

Solvation Structure and Ion Complexation of La³⁺ in a 1 Molal Aqueous Solution of Lanthanum Chloride

Speciation of La(III) Chloride Complexes in Water and Acetonitrile: A Density Functional Study

Structures and Energetics of Erbium Chloride Complexes in Aqueous Solution

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Stability Constants of Chloride Complexes of Lanthanum

Cited by 6 publications

References 17 publications

Solvation Structure and Ion Complexation of La3+ in a 1 Molal Aqueous Solution of Lanthanum Chloride

Solvation Structure and Ion Complexation of La3+ in a 1 Molal Aqueous Solution of Lanthanum Chloride

Speciation of La(III) Chloride Complexes in Water and Acetonitrile: A Density Functional Study

Structures and Energetics of Erbium Chloride Complexes in Aqueous Solution

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Solvation Structure and Ion Complexation of La³⁺ in a 1 Molal Aqueous Solution of Lanthanum Chloride

Solvation Structure and Ion Complexation of La³⁺ in a 1 Molal Aqueous Solution of Lanthanum Chloride