A Toolbox for Probing Bonding Properties in Lanthanide Metalorganic Systems via X-Ray Spectroscopic Methods

Recently, the assumption that lanthanide bonds are completely ionic has been under scrutiny, especially regarding tetravalent species like Ce(IV), where meaningful covalent contributions to bonding were found.[1] As part of the Collaborative Research Center “4f for Future” ’s mission, it aims to shine a light upon the bonding properties of novel molecular and nano-sized lanthanide-based compounds and the relationship to their physical properties and behavior. However, compounds synthesized within the project are often air and water, and sometimes light, sensitive. The measurement of such samples and the observation of their bonding properties using high energy resolution X-ray absorption and emission spectroscopy requires the development of technological, procedural and spectroscopic tools.
These tools and their development are showcased using two project examples, the comparison of bonding properties of two highly sensitive analogous Cerium metalorganic complexes with differing oxidation states and a benchmark experiment toward using microfluidics as a tool to observe the complexation of Lanthanum with chelating agents in-situ, allowing observation of changes in bonding throughout complexation. ... mehrHigh Resolution X-Ray Absorption Near Edge Spectra (HR-XANES) and Valence Band Resonant Inelastic X-Ray Scattering (VB-RIXS) are employed to observed the electronic structure of the molecule and draw conclusions on the present bonds and their properties. Technical developments that make measuring highly sensitive samples and unusual sample types possible are described.
The authors gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft through the Collaborative Research Centre ″4f for Future” project A1 (CRC 1573, project number 471424360) and the ERC Consolidator Grant “The Actinide Bond” (N°101003292) under the European Union’s Horizon 2020 program.

[1] aT. Vitova, P. W. Roesky, S. Dehnen, Communications Chemistry 2022, 5, 12; bS. G. Minasian, E. R. Batista, C. H. Booth, D. L. Clark, J. M. Keith, S. A. Kozimor, W. W. Lukens, R. L. Martin, D. K. Shuh, S. C. E. Stieber, T. Tylisczcak, X.-d. Wen, Journal of the American Chemical Society 2017, 139, 18052-18064; cT. Vitova, H. Ramanantoanina, B. Schacherl, L. Münzfeld, A. Hauser, R. S. K. Ekanayake, C. Y. Reitz, T. Prüßmann, T. S. Neill, J. Göttlicher, R. Steininger, V. A. Saveleva, M. W. Haverkort, P. W. Roesky, Journal of the American Chemical Society 2024, 146, 20577-20583.