Are Actinyl Cations Good Probes for Structure Determination in Solution by NMR?

We report on NMR spectroscopy, CAS-based method calculations, and X-ray diffraction of An V and An VI complexes with a neutral and slightly flexible TEDGA ligand. After checking that pNMR shifts mainly arise from pseudocontact interactions, we analyze pNMR shifts considering the axial and rhombic anisotropy of the actinyl magnetic susceptibilities. The results are compared to those of a previous study performed on [An VI O 2 ] 2+ complexes with dipicolinic acid. It is shown that 5f 2 cations (Pu VI and Np V ) make very good candidates for determining the structure of actinyl complexes in solution by 1 H NMR spectroscopy as shown by the invariance of the magnetic properties to the equatorial ligands, as opposed to the Np VI complexes with a 5f 1 configuration.