JRP 06-14

Partners

FZK

ULG

Contact

Andreas Geist
Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung P.O. Box 3604, 76021 Karlsruhe, Germany
Phone +49-7247-82-6249
E-mail e-mail

Investigations of the coordination and electronic structure of An(III)/Ln(III) complexed with N-donor ligands

Status

 
Terminated - Planned from April 2007 till October 2008

Goals

Extractants of the BTP and BTBP type have an excellent selectivity for An(III) over Ln(III). However, the selectivity’s origin is not clearly understood. Comparative EXAFS investigations on the solution structures of M(BTP)33+ complexes with M = Eu, Gd, Lu, Am, Cm do not show differences which would manifest the much discussed covalence effect. Only for M = U is any indication of higher covalent character of the U(III)-N binding observed. The question arises if the reasons for selectivity lie in kinetics of the interface reaction during extraction or if they rest in solvation or electronic effects. The aim of this project is to vary both donor ligand electronic structure and organic diluent and then elucidate this variation’s effect on geometrical / electronic structure, complex stability, and complex formation kinetics. This will yield fundamental information towards understanding differences between An(III) and Ln(III) complexation with N-donor ligands.
We will synthesise BTP and BTBP derivatives bearing moieties such as -CF3, -NO2, thusmodifying their electronic properties for further study. Complexes formed between such ligands and An(III) or Ln(III) will be investigated in non-aqueous liquid phases using a variety of complementary techniques (NMR, XAFS, RIXS, and TRLFS). The experimental program will be complemented by quantum chemical calculations.

Expected results

By comparing the results from complexes of the modified ligand with An(III) to those with Ln(III), and to results from “classical” BTP and BTBP complexes we will identify differences between An(III) and Ln(III) coordination structure, stability, electronic properties, and in complex formation kinetics.

Reports