XAFS and spectroscopic characterization for the structure and electronic structure of Ce-DMDPhPDA complexes in methanol

The structural parameters and the electronic structure of the complex between cerium(III) and N,N′-dimethyl-N,N′-diphenylpyridine-2,6- carboxyamide (DMDPhPDA) were studied by XAFS, and both luminescence and excitation spectroscopes. We investigated the fundamental aspects of this material as the ligand is promising for the separation of trivalent actinides and lanthanides. The Ce-K XAFS spectra were measured at the SPring-8 synchrotron facility in Japan. It was determined that the bond distances between the carbonyl oxygen and cerium, and between the pyridyl nitrogen and cerium were about 2.49 and 2.67 Å, respectively. The angle between the Ce-N bond and the pz axis of the lone pair of the pyridyl nitrogen is 180° for the solution state, suggesting covalent interaction between cerium and the nitrogen of the DMDPhPDA ligand. Emission from this system is severely quenched, and red-shifts, and supports the presence of a strong inner sphere complexation between cerium and the nitrogen atom of the pyridyl group. From the XANES spectrum, the oxidation state of cerium was determined to be trivalent. © Physica Scripta 2005.