Abstract
Paramagnetic Nuclear Magnetic Resonance (pNMR) plays an important role in structural determination of complexes in solution, particularly in biological systems where pNMR chemical shifts are induced by lanthanide cations. The use of actinides (An) for complex structure determination has never really been employed while it could be useful in nuclear fuel research and environmental science.For [AnO2]2+ complexes (An = Np, Pu), chemical shifts in 1H pNMR are mainly induced by the pseudocontact contribution, corresponding to the magnetic interaction between the 5f unpaired electron of the metallic cation and the proton nuclear spin. This pseudocontact contribution depends on both the magnetic susceptibility anisotropy of the complex and a geometric factor related to proton positions in the complex. The aim of this work is to carry on investigations about the relationship between 1H pNMR shifts and their coordinates within a complex taking into account molecular moves of the alkyl chains by classical molecular dynamics (MD) simulations. To this end, MD simulations have been perfor- med with [AnO2]2+ cations and flexible ligands such as TEDGA (a diglycolamide) and valine (an amino acid). Then, the calculated geometric factors are confronted to experimental 1H pNMR chemical shifts.This study provides important structural information on the AnVI and AnV complexes, such as the speciation in solution, the different coordination modes and give access to the magnetic susceptibility anisotropy parameters of the paramagnetic cations.