title: Topological Study of Bonding in Aquo and Bis(triazinyl)pyridine Complexes of Trivalent Lanthanides and Actinides: Does Covalency Imply Stability?
abstract: The geometrical and electronic structures of Ln[(H2O)9]3+and [Ln(BTP)3]3+, where Ln = Ce-Lu, have been evaluated at the density functional level of theory using three related exchange-correlation (xc-)functionals. The BHLYP xc-functional was found to be most accurate, and this, along with the B3LYP functional, was used as the basis for topological studies of the electron density via the quantum theory of atoms in molecules (QTAIM). This analysis revealed that, for both sets of complexes, bonding was almost identical across the Ln series and was dominated by ionic interactions. Geometrical and electronic structures of actinide (An = Am, Cm) analogues were evaluated, and [An(H2O)9]3++ [Ln(BTP)3]3+→ [Ln(H2O)9]3++ [An(BTP)3]3+exchange reaction energies were evaluated, revealing Eu ↔ Am and Gd ↔ Cm reactions to favor the An species. Detailed QTAIM analysis of Eu, Gd, Am, and Cm complexes revealed increased covalent character in M-O and M-N bonds when M = An, with this increase being more pronounced in the BTP complexes. This therefore implies a small electronic contribution to An-N bond stability and the experimentally observed selectivity of the BTP ligand for Am and Cm over lanthanides.
authors: Department of Chemistry, Lancaster University , Bailrigg, Lancaster LA1 4YB, U.K.
authors: Izaak
authors: I
authors: Fryer-Kanssen
authors: National Nuclear Laboratory , Chadwick House, Birchwood Park, Warrington WA3 6AE, U.K.
authors: Jonathan
authors: J
authors: Austin
authors: Department of Chemistry, Lancaster University , Bailrigg, Lancaster LA1 4YB, U.K.
authors: Andrew
authors: A
authors: Kerridge