Yb(III) and U(VI) complexes with 1-hydroxy-ethyliden-bis-phosphonic acid (HEDP) and 3,4,3-LI(1,2-HOPO) (LIHOPO)

For Yb(III)–HEDP, 1H and 31P NMR data infer formation of a well-defined and kinetically stable polynuclear complex at pH ~13.
Correspondingly, the complex is hypothesized to contain at least three Yb atoms along with μ2/3 OH and/or μ3/6 O – features of
characteristic interatomic distance suited to be resolved by EXAFS at the Yb-L3 edge.
For U(VI)–HOPO, unprecedented uranyl-oxygen 17O NMR chemical shifts along with peculiar luminescence properties suggest that the UOyl
bond lengths in the 1:1(aq) and 2:1(s) (M:L) complexes are significantly longer than in usual O=U(VI)=O entities, implying partial U(V)
character. For verification, one liquid (1:1 complex) and one solid sample (2:1 complex) is measured with EXAFS as well as HERFD-XAS at the
U L3-edge. Eventually, the hydroxypyridinone ligand seems to push U formally in +VI state towards +V which, once verified, advances
knowledge on UVI/V coordination and redox chemistry.