Issue 14, 2023

Coordination and thermodynamic properties of aqueous protactinium(v) by first-principle calculations

Abstract

Protactinium (Z = 91) is a very rare actinide with peculiar physico-chemical properties. Indeed, although one may naively think that it behaves similarly to either thorium or uranium by its position in the periodic table, it may in fact follow its own rules. Because of the quite small energy gap between its valence shells (in particular the 5f and 6d ones) and also the strong influence of relativistic effects on its properties, it is actually a challenging element for theoretical chemists. In this article, we combine experimental information, chemical arguments and standard first-principle calculations, complemented by implicit and explicit solvation, to revisit the stepwise complexation of aqueous protactinium(V) with sulfate and oxalate dianionic ligands (SO42− and C2O42−, respectively). From a methodological viewpoint, we notably conclude that it is necessary to at least saturate the coordination sphere of protactinium(V) to reach converged equilibrium constant values. Furthermore, in the case of single complexations (i.e. with one sulfate or oxalate ligand bound in the bidentate fashion), we show that it is necessary to maintain the coordination of one hydroxyl group, present in the supposed [PaO(OH)]2+ precursor, to obtain coherent complexation constants. Therefore, we predict that this hydroxyl group is maintained in the formation of 1 : 1 complexes while we confirm that it is withdrawn when coordinating three sulfate or oxalate ligands. Finally, we stress that this work is a first step toward the future use of theoretical predictions to elucidate the enigmatic chemistry of protactinium in solution.

Graphical abstract: Coordination and thermodynamic properties of aqueous protactinium(v) by first-principle calculations

Supplementary files

Article information

Article type
Paper
Submitted
20 Jan 2023
Accepted
20 Mar 2023
First published
20 Mar 2023
This article is Open Access
Creative Commons BY-NC license

Phys. Chem. Chem. Phys., 2023,25, 10033-10041

Coordination and thermodynamic properties of aqueous protactinium(V) by first-principle calculations

H. Oher, J. Delafoulhouze, E. Renault, V. Vallet and R. Maurice, Phys. Chem. Chem. Phys., 2023, 25, 10033 DOI: 10.1039/D3CP00323J

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