Constantes de formation des complexes de stoechiometrie 1:1 et 1:2 ainsi que des complexes mixtes formes entre le plutonium(III) et divers acides amino-polyacetiques

Effect of Mg and Ca on the Stability of the MRI Contrast Agent Gd–DTPA in Seawater

“…Their value for pK a2 is more similar to published values for pK a1 . In addition, their values for pK a3 (3.39) and pK a1 (1.13) are remarkably close to, respectively, the average of our values for pK a2 and pK a4 (3.38) at I = 0.7 M and the average of the values for pK a−1 and pK a0 (1.12) at I = 1 (KCl) reported by Merciny et al (1978) and Mioduski (1980). It seems that pK a3 was not resolved in the regression, causing an upward shift of the lower pK ai .…”

“…At 25 • C, reported values of pK a0 are 1.75 in 0.1 M KNO 3 (Letkeman and Martell, 1979) and 1.67 in KCl at I = 1 (Merciny et al, 1978;Mioduski, 1980), while somewhat lower values are found at lower temperature: 1.45 in NaCl (I = 0.11) at 20 • C (Matorina et al, 1969) and 1.22 in NaClO 4 (I = 1) at 21 • C (Kragten and Decnop-Weever, 1983). The same authors report congruent values for pK a−1 under the given conditions: 0.75 (Kragten and Decnop-Weever, 1983), 0.88 (Merciny et al, 1978;Mioduski, 1980), and 0.89 (Matorina et al, 1969), except for Letkeman and Martell (1979), who found a value of 1.45. Only Mioduski (1980) reports a value for pK a−2 (0.81 ± 0.05), but Martell et al (2004) estimate that it is probably less than zero.…”

Coordination Modes in the Formation of the Ternary Am(III), Cm(III), and Eu(III) Complexes with EDTA and NTA: TRLFS, 13C NMR, EXAFS, and Thermodynamics of the Complexation

“…For Am 3+ and Cm 3+ , no such constants are available. However, log β 111 of 20.80 ± 0.02 has been measured for the ternary complex, Pu(EDTA)(NTA) 4- at I = 1.0 m (KCl) and T = 25 °C 6 Stability Constants of Am 3+ , Cm 3+ , and Eu 3+ with EDTA+NTA (log β 111 ) at pcH = 3.60, I = 6.60 m (NaClO 4 ), T = 0−60 °C a temp (°C) I (m)methodAmCmEuref 0 6.60 NaClO 4 sx 23.73 ± 0.08 23.80 ± 0.09 24.40 ± 0.10 p.w 25 6.60 NaClO 4 sx 25.73 ± 0.09 25.91 ± 0.08 25.96 ± 0.09 p.w 25 0.5 KNO 3 pot − − 21.08 ± 0.18* 3 20 1.0 KCl abs − − 20.4 ± 0.20 7 20 0.1 KNO 3 pot − − 22.38 ± 0.09 5 20 0.1 KNO 3 1 H NMR − − 22.40 ± 0.09 6 45 6.60 NaClO 4 sx 26.82 ± 0.11 27.39 ± 0.10 27.44 ± 0.11 p.w 60 6.60 NaClO 4 sx 28.06 ± 0.11 28.80 ± 0.10 28.71 ± 0.11 p.w a Sm, sx = solvent extraction, pot = potentiometric titration, abs = absorption spectroscopy, p.w.…”

“…There are many reports on the formation of the ternary complexes of Ln(EDTA) - with ligands such as acetate (Ac), oxalate (Ox), diglycolate (Dgl), iminodiacetate (IDA), 8-hydroxyquilnoline-5-sulfonate (HQS), NTA, etc. − Studies of the formation of ternary complexes of actinides are relatively few. Those investigated include UO 2 (NTA) - and Th(NTA) + with dicarboxylates, Th(EDTA) 0 and Th(CDTA) 0 (CDTA = 1,2-cyclohexanedinitrilotetraacetate) with IDA, HQS, and salicylate (SA) etc., , Pu(HEDTA) 0 (HEDTA = N - hydroxyethylethylenediaminetriacetate) or Pu(EDTA) - with NTA, IDA or Gly (glycinate), and Pu(EDTA) 0 with Cit (citrate) and CO 3 2- (carbonate) . These studies reflect the importance of size of metal cations, ligand basicity, steric requirements of the ligands, and some specific metal to secondary ligand interactions on the formation of the ternary complexes.…”

Pu(iii) and Cm(iii) in the presence of EDTA: aqueous speciation, redox behavior, and the impact of Ca(ii)

“…The authors identified 6 different aqueous Pu( iii )–EDTA species: Pu(EDTA) − , Pu(HEDTA)(aq), Pu(EDTA) 2 5− , Pu(EDTA) 2 H 4− , Pu(EDTA) 2 H 2 3− , and Pu(EDTA) 2 H 3 2− ; the first two species were identified through a series of titrations from pH 1.56–2.39, whereas the latter four species were identified at higher pH and exhibited significantly weaker complexation. The NEA-TDB did not select the latter four species because “ in view of the weak complexation effects, the ambiguities involved in extrapolating highly charged species from 1 M KCl to zero ionic strength using estimated SIT interaction parameters, and the fact that no other reliable study has yet confirmed the results of [Merciny et al 32 ], no values are selected in this review for 1:2 complexes” . 21 …”