title: 6-(3,5-Dimethyl-1H-pyrazol-1-yl)-2,2'-bipyridine as ligand for actinide(III)/lanthanide(III) separation.
abstract: With the aim of better understanding the selectivity of the established system 2,6-ditriazinylpyridine (BTP) for actinide(III)/lanthanide(III) separations, a related model system was synthesized and studied. The N donor complexing ligand 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2,2'-bipyridine (dmpbipy) was synthesized having a fused N heterocycle ring structure modified from the BTP partitioning ligand, and its extraction performance and selectivity for trivalent actinide cations over lanthanides was evaluated. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and time-resolved laser fluorescence spectroscopy (TRLFS) results show that 1:1 complexes are formed, unlike the 1:3 complex for BTP systems. The equilibrium constant for curium complex formation with dmpbipy was determined to be log K = 2.80, similar to that for nitrate. The Gibbs free energy, ΔG(20 °C), of 1:1 Cm-dmpbipy formation in n-octan-1-ol was measured to be -15.5 kJ/mol. The dmpbipy ligand in 1-octanol does not extract Am(III) Eu(III) from HNO(3) but was found to extract Am(III) with limited selectivity over Eu(III) (SF(Am(III)/Eu(III)) ≈ 8) dissolved in 2-bromohexanoic acid and kerosene at pH > 2.4.
authors.affiliation: Institut für Anorganische Chemie, Karlsruher Institut für Technologie, Engesserstrasse 15, 76131 Karlsruhe, Germany.
authors.forename: Denise
authors.initials: D
authors.lastname: Girnt
authors.forename: Peter W
authors.initials: PW
authors.lastname: Roesky
authors.forename: Andreas
authors.initials: A
authors.lastname: Geist
authors.forename: Christian M
authors.initials: CM
authors.lastname: Ruff
authors.forename: Petra J
authors.initials: PJ
authors.lastname: Panak
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Denecke