Abstract
Density functional theory (B3LYP) and correlated molecular orbital theory (CCSD(T)) calculations were used to predict the properties of novel actinide-fluoride complexes formed by the addition of a fluorine to AnF<sub>n</sub> compounds, with actinides in their normal maximum oxidation state (n), leading to the formation of an ion-pair complex [AnF<sub>n-1</sub><sup>+</sup>][F<sub>2</sub><sup>-</sup>] for the earlier actinides (Ac, Th, and Pa). UF<sub>7</sub> prefers a structure with a weakly associated fluorine, forming a [UF<sub>6</sub>][F<sup>•</sup>] complex, likely due to steric hindrance. Ionization of [AnF<sub>n-1</sub><sup>+</sup>][F<sub>2</sub><sup>-</sup>] forms a weakly bound [AnF<sub>n-1</sub><sup>+</sup>][F<sub>2</sub>] complex. Ionization of AnF<sub>n</sub> leads to the formation of [AnF<sub>n-2</sub><sup>2+</sup>][F<sub>2</sub><sup>-</sup>] complex so that the electron is not removed from the actinide and maintains the An oxidation state. The ionization energies, An-F bond dissociation energies, and enthalpy for the loss of F<sub>2</sub><sup>0/-</sup> of these complexes are in agreement with the available experimental data. The fluoride affinities of AnF<sub>n</sub> and the electron affinities of AnF<sub>n+1</sub> were calculated. The fluoride affinities are large and comparable to those of AsF<sub>5</sub> and SbF<sub>5</sub> so they are strong Lewis acids. The electron affinities are sizable, indicating that AnF<sub>n+1</sub><sup>-</sup> will be powerful oxidizing agents and should be considered in models of molten salt reactors when fluoride is present.