Aqueous complexation of citrate with neodymium(iii) and americium(iii): a study by potentiometry, absorption spectrophotometry, microcalorimetry, and XAFS

Abstract

The aqueous complexation of Nd(III) and Am(III) with anions of citrate was studied by potentiometry, absorption spectrophotometry, microcalorimetry, and X-ray absorption fine structure (XAFS). Using potentiometric titration data fitting the metal-ligand (L) complexes that were identified for Nd(III) were NdHL, NdL, NdHL2, and NdL2; a review of trivalent metal-citrate complexes is also included. Stability constants for these complexes were calculated from potentiometric and spectrophotometric titrations. Microcalorimetric results concluded that the entropy term of complex formation is much more dominant than the enthalpy. XAFS results showed a dependence in the Debye-Waller factor that indicated Nd(iii)-citrate complexation over the pH range of 1.56-6.12.

Selective extraction of americium(III) over europium(III) ions in nitric acid solution by NTAamide(C8) using a novel water-soluble bisdiglycolamide as a masking agent

“…An isosbestic point observed at 581.3 nm suggested the presence of two absorbing Nd(III) species including Nd(NO3)3. The stability constant of NdL 3+ (L represents NTAamide(C8)) was calculated as 8.27 ± 0.06 [41].…”

Uranium(VI) Complexes with a Calix[4]arene‐Based 8‐Hydroxyquinoline Ligand: Thermodynamic and Structural Characterization Based on Calorimetry, Spectroscopy, and Liquid–Liquid Extraction

“…The positive entropyo fc oordination for the second uranyl ion can be caused by the release of nitrate ions and hydration water from UO 2 (NO 3 ) 2 ·6H 2 O. [48][49][50] The reorganization of acetonitrile aroundt he complex can also contribute to an increase in the entropy. [48] The entropy value shoulda lso be positive in the complexation of the first uranyl ion.…”

Role of the Hydroxo Group in the Coordination of Citric Acid to Trivalent Americium

“…A significant number of thermodynamic studies were devoted to the complexation of An(III) or lanthanides (Ln), , with citric acid in various media at various ionic strengths. The outcomes of these studies led to the determination of conditional complexation constants without a precise description of the corresponding complexes.…”

“…As far as we know, only two of them report structure characterizations on the An(III)‐citric acid system, determining the number of water molecules in the primary coordination sphere by time resolved laser‐induced fluorescence spectroscopy (TRLFS) , . In order to supplement the Am system, a number of other studies reported the structural characterizations on the Ln(III) complexes, that can be considered as a analogues of An(III) with close ionic radii . One attempt reports a similar structure characterization of Nd(III) complexes by extended X‐ray absorption fine structure (EXAFS) spectroscopy, the results of which appear to be incomplete.…”

“…In order to supplement the Am system, a number of other studies reported the structural characterizations on the Ln(III) complexes, that can be considered as a analogues of An(III) with close ionic radii . One attempt reports a similar structure characterization of Nd(III) complexes by extended X‐ray absorption fine structure (EXAFS) spectroscopy, the results of which appear to be incomplete. The Eu(III)‐citric acid system was investigated by infrared (IR) spectroscopy .…”