RESUMO
The first comprehensive structural and extraction study of a 2,2'-bipyridine-6,6'-dicarboxamide (L diamide) extractant for U, Np, Pu, Th, Am, and Eu ions showed great potential for actinide separation due to steric hindrance of the amidic side phenyl ring of the given compound. The study of the complexes of An(VI) and Th(IV) with 2,2'-bipyridyldicarboxamide-type extractants demonstrated the structure of the extraction species for the first time. Investigation of the extraction properties with the radiometric and millimolar quantities of actinides showed similar extraction trends. For the first time, a metal-ion-induced phenyl-ring rotation restriction was found for the U, Th, and Eu complexes by employing temperature-dependent dynamic NMR. A study of the solution behavior of the complexes accompanied by density functional theory modeling studies elucidated the mechanism of the unusual C-N bond rotation restriction induced by metal coordination.
RESUMO
The magnetic properties of LnIII and AnIII complexes formed with dipicolinate ligands have been studied by NMR spectroscopy. To know precisely the geometries of these complexes, a crystallographic study by single-crystal X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) in solution was performed. Several methods to separate the paramagnetic shifts observed in the NMR spectra were applied to these complexes. Methods using a number of nuclei of the dipicolinate ligands revealed an abrupt change in the geometries of the complexes and a metal-ligand interaction in the middle of the lanthanide series. A study of the variation of the paramagnetic shifts with temperature demonstrated that higher-order terms of the dipolar and contact contributions are required, especially for the lightest LnIII and almost all the studied AnIII . Bleaney's parameters