A comparative study of actinide complexation in three ligand systems with increasing complexity

The complexation of thorium, neptunium and plutonium at oxidation state +IV with three ligands of increasing complexity has been investigated. These ligands are relevant for bio inorganic systems. The first ligand is the small nitrilotriacetic acid that often play the role of protecting ligands agai...

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Published inJournal of physics. Conference series Vol. 190; no. 1; p. 012185
Main Authors Jeanson, A, Dahou, S, Guillaumont, D, Moisy, P, Auwer, C Den, Scheinost, A, Hennig, C, Vidaud, C, Subra, G, Solari, P L
Format Journal Article
LanguageEnglish
Published Bristol IOP Publishing 01.11.2009
Subjects
Cations
Comparative studies
Complex systems
Complexation
Complexity
Coordination
Ligands
Neptunium
Nitrilotriacetic acid
Oxidation
Physics
Plutonium
Quantum chemistry
Steric effects
Thorium
Transferrin
Transition metals
Valence
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Summary:The complexation of thorium, neptunium and plutonium at oxidation state +IV with three ligands of increasing complexity has been investigated. These ligands are relevant for bio inorganic systems. The first ligand is the small nitrilotriacetic acid that often play the role of protecting ligands against hydrolysis. EXAFS results for the Th to Pu series have been correlated to quantum chemical calculations and show an homogeneous behavior of the actinide at oxidation state +IV. For larger ligands, steric effects may become significant and one can ask how the ligand may accommodate the large actinide cation coordination sphere. Model pentapeptides have been synthesized and tested as complexing agents. Comparison with NTA shows that the molecular arrangements are radically different. The third ligand system is transferrin, a diferric metalloptrotein that is well known to coordinate a large variety of cations from transition metals of f-elements. Metalloproteins bear primary, secondary and tertiary structures that all play a crucial role in bonding. At a given oxidation state (+IV), but for various atomic numbers (Th, Np, Pu) EXAFS data at the cation LIII edge exhibit significant coordination discrepancies that are related to a changes in protein geometry. In that sense, the metalloprotein may be viewed as a complex system.
ISSN:1742-6596
1742-6588
1742-6596
DOI:10.1088/1742-6596/190/1/012185