Comparison of structures and energies of metal complexes coordinated with hydroxyoxime and carboxylic acid extractants by using molecular simulations

Abstract

Correlation between structures and energies of cobalt(II) (Co) and manganese(II) (Mn) complexes with the hydroxyoxime extractant, LIX63 and/or the carboxylic acid extractant, Versatic acid 10 (VA10), were investigated using molecular dynamics (MD) calculations and density functional theory (DFT) calculations. The results of the MD calculations show that the form of the metal complex with both single and multiple extractants varied significantly with the numbers of coordinated extractant molecules and coordination sites. However, there was no correlation between the frequency of appearance of the metal complexes and the formation energy obtained from DFT calculations. In the case of Co or Mn complexes with LIX63 and VA10, these extractant molecules were tightly packed around each metal ion and there were little differences between the formation energies of the complexes. Our results suggest that structural and energetic stabilization is responsible for the synergistic effect of solvent extraction.