title: Evidence for covalence in a N-donor complex of americium(III).
abstract: The molecular origin of the selectivity of N-donor ligands, such as alkylated bis-triazinyl pyridines (BTPs), for actinide complexation in the presence of lanthanides is still largely unclear. NMR investigations of an Am(nPrBTP)3(3+) complex with a (15)N labelled ligand showed that it exhibits large differences in (15)N chemical shift for coordinating N-atoms in comparison to both lanthanide(III) complexes and the free ligand. The temperature dependence of NMR chemical shifts observed for this complex indicates a weak paramagnetism. This fact and the observed large chemical shift for bound nitrogen atoms allow us to conclude that metal-ligand bonding in the reported Am(III) N-donor complex has a larger share of covalence than in lanthanide complexes. This may account for the observed selectivity.
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute for Nuclear Waste Disposal (INE), P.O. Box 3640, 76021 Karlsruhe, Germany. Peter.Kaden@kit.edu.
authors.forename: Christian
authors.initials: C
authors.lastname: Adam
authors.forename: Peter
authors.initials: P
authors.lastname: Kaden
authors.forename: Björn B
authors.initials: BB
authors.lastname: Beele
authors.forename: Udo
authors.initials: U
authors.lastname: Müllich
authors.forename: Sascha
authors.initials: S
authors.lastname: Trumm
authors.forename: Andreas
authors.initials: A
authors.lastname: Geist
authors.forename: Petra J
authors.initials: PJ
authors.lastname: Panak
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Denecke