L. Ziberna, Ph. Guilbaud, E. Guillam, and M. Duvail
Journal of Molecular Liquids, 438, 128711 (2025)
The study explores the formation of solvent extraction aggregates composed of Eu(NO3)3 salts with DMDOHEMA molecules solvated in n-heptane using classical molecular dynamics simulations at two Eu(NO3)3 salt concentrations, namely 0.015 and 0.126 mol L-1. For both concentrations, the main aggregates are predominantly in the form of Eumonomers and dimers, with a higher ratio of monomers. However, increasing the Eu(NO3)3 concentration tends to increase the number of dimers. The average Eumonomer is composed of three nitrate anions and 3–4 DMDOHEMA molecules, whereas the average dimer is composed of six nitrate anions and 6 DMDOHEMA molecules. For both types of aggregates, the influence of the Eu(NO3)3 concentration has been observed only in the number of water molecules involved in each kind of aggregate. Furthermore, we demonstrated that the presence of nitrate anions and especially the number of water molecules in the polar core of the aggregates favors the formation of dimers, with various types of nitrate-water bridges. We highlighted that the dynamics of water in the vicinity of the cations, as well as the availability of ligands capable of forming hydrogen bonds within the coordination shell of nearby ions, are crucial for understanding the aggregation mechanisms.
