Modeling polonium complexes in solution
Résumé
Polonium is a heavy and rare element standing under the number 84 on the Periodic Table. It is a naturally occurring element, though its abundance is among the weakest ones. It is highly toxic, which hinders experimental studies aiming at revealing its properties. Nevertheless, polonium was used as a heat source in the space industry, as an alpha-emission source, or as a static eliminator, before cheaper and safer alternatives replaced it. It is also a famous poison, with currently no good enough antidote. A better understanding of its chemistry could potentially help in better detecting it and also characterizing its speciation in natural media and industry and also in designing better cure in the case of ingestion. However, the available quantities and the complex manipulation of this element make its characterization arduous. In this context, we perform quantum chemistry calculations to predict the properties of polonium species.
In our project, we study polonium complexes in the gas phase and in solution. We consider its most stable oxidation state in solution, i.e. +IV. Following previous work [1,2], two families of complexes were first chosen for performing a methodological study in the gas phase. While the [Po(H2O)n]4+ (n = 1–9) series was selected to get fundamental knowledge of hydration, the chlorinated [PoClm]4–m (m = 1–8) complexes were studied because of experimental evidence for the formation of such species in solution. As an extension to a benchmark study in the gas phase on geometries and interaction energies, ground state bonding descriptors were obtained [3]. Therefore, information on coordination numbers and chemical bonding were both derived.
Following the idea to connect with established experimental data, state-of-the-art excited-state calculations have been performed on two potentially occurring chlorinated complexes, revealing once more the difficulty of interpreting from scratch the few spectra that are available for polonium species. We thus emphasize the need for performing more calculations of predictive quality to unravel this enigmatic chemistry.
References:[1] R. Ayala, J. M. Martinez, R. R. Pappalardo, A. Muñoz-Paez and E. Marcos Sánchez, J. Phys. Chem. B, 2008, 112, 5416–5422.
[2] A. Stoanov, J. Champion and R. Maurice, Inorg. Chem., 2019, 58, 7036-7043.
[3] N. Zhutova, F. Réal, V. Vallet and R. Maurice, Phys. Chem. Chem. Phys., 2022, 24, 26180-26189.
In our project, we study polonium complexes in the gas phase and in solution. We consider its most stable oxidation state in solution, i.e. +IV. Following previous work [1,2], two families of complexes were first chosen for performing a methodological study in the gas phase. While the [Po(H2O)n]4+ (n = 1–9) series was selected to get fundamental knowledge of hydration, the chlorinated [PoClm]4–m (m = 1–8) complexes were studied because of experimental evidence for the formation of such species in solution. As an extension to a benchmark study in the gas phase on geometries and interaction energies, ground state bonding descriptors were obtained [3]. Therefore, information on coordination numbers and chemical bonding were both derived.
Following the idea to connect with established experimental data, state-of-the-art excited-state calculations have been performed on two potentially occurring chlorinated complexes, revealing once more the difficulty of interpreting from scratch the few spectra that are available for polonium species. We thus emphasize the need for performing more calculations of predictive quality to unravel this enigmatic chemistry.
References:[1] R. Ayala, J. M. Martinez, R. R. Pappalardo, A. Muñoz-Paez and E. Marcos Sánchez, J. Phys. Chem. B, 2008, 112, 5416–5422.
[2] A. Stoanov, J. Champion and R. Maurice, Inorg. Chem., 2019, 58, 7036-7043.
[3] N. Zhutova, F. Réal, V. Vallet and R. Maurice, Phys. Chem. Chem. Phys., 2022, 24, 26180-26189.