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

We report on NMR spectroscopy, CAS-based method calculations,andX-ray diffraction of An(V) and An(VI) complexeswith a neutral and slightly flexible TEDGA ligand. After checkingthat pNMR shifts mainly arise from pseudocontact interactions, weanalyze pNMR shifts considering the axial and rhombic anisotropy ofthe actinyl magnetic susceptibilities. The results are compared tothose of a previous study performed on [An(VI)O(2)](2+) complexes with dipicolinic acid. It is shown that5f(2) cations (Pu-VI and Np-V) make verygood candidates for determining the structure of actinyl complexesin solution by H-1 NMR spectroscopy as shown by the invarianceof the magnetic properties to the equatorial ligands, as opposed tothe Np-VI complexes with a 5f(1) configuration. We report on NMR spectroscopy, CAS-basedmethod calculations,and X-ray diffraction of An(V) and An(VI) complexeswith a neutral and slightly flexible TEDGA ligand. After checkingthat pNMR shifts mainly arise from pseudocontact interactions, weanalyze pNMR shifts considering the axial and rhombic anisotropy ofthe actinyl magnetic susceptibilities. It is shown that 5f(2) cations (Pu-VI and Np-V) make very good candidatesfor determining the structure of actinyl complexes in solution by H-1 NMR spectroscopy as shown by the invariance of the magneticproperties to the equatorial ligands, as opposed to the Np-VI complexes with a 5f(1) configuration.

Automated summary

We investigated An(V) and An(VI) complexes with a neutral and slightly flexible TEDGA ligand using NMR spectroscopy, CAS-based method calculations, and X-ray diffraction. By analyzing pNMR shifts considering the axial and rhombic anisotropy of the actinyl magnetic susceptibilities, we found that 5f(2) cations (Pu-VI and Np-V) are ideal for determining the structure of actinyl complexes in solution by H-1 NMR spectroscopy. In contrast, Np-VI complexes with a 5f(1) configuration showed different magnetic properties.