Actinide bonding properties – stability relations probed by high resolution X-ray spectroscopy

Understanding the electronic structure and chemical bonding properties of the actinide (An) elements poses a great challenge [1]. The An4,5 absorption edges core-to-core and valence band resonant inelastic X-ray scattering (CC/VB-RIXS) and high energy resolution X-ray absorption near edge structure (HR-XANES) techniques probe the occupied and unoccupied parts of the valence band of the actinide elements with extraordinary energy resolution and in combination with computational quantum chemistry detailed information on the chemical bonding can be obtained [1]. All An M4,5 edge RIXS and HR-XANES studies are performed at the ACT station of the CAT-ACT beamline at the KIT Light Source [2].
It will be demonstrated that the ionic bond of Sm(II) with (cyclononatetraenyl =CNT) in [Sm(CNT2)] can be modulated and becomes covalent by photon induced transfer of Sm f electrons to Sm d/s orbitals. This photon induced change of bonding properties can potentially activate the rather chemically inert [Sm(CNT2)] and can be applied for further lanthanide molecular materials
The stabilization of uranyl(V) (UO21+) by Fe(II) in natural systems remains an open question in uranium chemistry. ... mehrStabilization of UVO2 1+ by Fe(II) against disproportionation was also demonstrated in molecular complexes. However, the relation between the Fe(II) induced stability and the change of the bonding properties have not been elucidated up to date. It will be shown that U(V) – oaxial bond
covalency decreases upon binding to Fe(II) inducing redirection of electron density from the U(V) – oaxial bond towards the U(V) – equatorial bonds thereby increasing bond covalency. Our results indicate that such increased covalent interaction of U(V) with the equatorial ligands resulting from iron binding lead to higher stability of uranyl(V).
[1] Vitova, T. et al. Nature Communications 2017, 8, 16053.
[2] Schacherl, B. et al. Journal of Synchrotron Radiation 2022, 29 (1), 80-88.
[3] Bagus, P. S. et al. Inorganic Chemistry 2021, 60 (21), 16090-16102.
[4] Vitova, T. et al. Inorganic Chemistry 2020, 59 (1), 8-22.
[5} Vitova, T. et al., M. Mazzanti, L. Maron et al., submitted
[6] Neill, T. et al, in preparation