Uranyl(VI) Complexation by Sulfonate Ligands: A Relativistic Density Functional and TRLFS Study


Uranyl(VI) Complexation by Sulfonate Ligands: A Relativistic Density Functional and TRLFS Study

Kremleva, A.; Zhang, Y.; Shor, A. M.; Krüger, S.; Joseph, C.; Raditzky, B.; Schmeide, K.; Sachs, S.; Bernhard, G.; Rösch, N.

To study the role of sulfonate functional groups of humic substances in uranyl(VI) complexation, all-electron density functional calculations and time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied using small sulfonate ligands as models. A thiolate ligand was explored for comparison. As in an earlier experiment, 4-hydroxy¬benzenesulfonic acid (HBSA) and benzenesulfonic acid (BSA) were examined and compared to methylsulfonic acid (MSA). Structural parameters as well as energetic aspects of uranyl complexes by BSA and HBSA ligands were determined to be rather similar, in contrast to earlier experimental findings. The present TRLFS measurements show complexation of uranyl by both ligands in agreement with the computational results. Overall, the combined computational and experimental results indicate that sulfonate groups play only a minor role in uranyl complexation by sulfonate groups of humic substances because of the rather low stability constants.

Keywords: Density functional calculations; time resolved spectroscopy; TRLFS; uranium; sulfonates

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Publ.-Id: 16835