Crystallography, DFT study and nature of the bonding in the series of AnO22+ acetates (An = U, Np, Pu)

Abstract

We report the crystal structures of actinyl acetates comprising infinite chains [AnO₂(OOCCH₃)₂(H₂O)]_n (An = U, Np, Pu). All the three compounds studied at 100 K are isostructural and crystallize in the monoclinic crystal system. For the U compound, orthorhombic modification was found to be stable at room temperature. It was found that the main force governing this transition is the change in hydrogen bonding between neighbouring chains. For Np and Pu compounds, high-temperature polymorphs were not refined at temperatures up to 296 K. The nature of the bonding within the isostructural low temperature An acetate series was investigated theoretically through the implementation of DFT calculations and QTAIM analysis. Energetic and electronic characteristics relevant to the observed changes in crystal structures were identified. Overall, a new series of crystal structures and computational results contribute to the understanding of bonding in actinyl ion systems.