Real-space bonding analysis of tetravalent actinide complexes with N-donor ligands

The electronical properties of f-elements, especially of the actinides, are a very puzzling topic to investigate. The frontier orbitals (5f, 6d, 7s) all lying in a similar energy regime along with open shells and relativistic effects contribute to a very complex situation, where single-reference methods like DFT and Hartree-Fock are not suitable any more1. In recent years, the investigation of actinides in combination with organic ligands revealed a very rich chemistry with many forms of coordination and chemical bonding. Besides that, many visually appealing and intuitive tools have been developed, with which the chemical bond can be analysed. These tools for bond analysis include natural-bonding orbitals (NBO) and the methods of real-space bonding analysis, e.g. quantum theory of atoms in molecules (QTAIM), bond path analysis, the electron localisability indicator (ELI-D) and non-covalent interaction plots (NCI). The aim of this study is therefore to apply these bond analysis tools to a range of tetravalent actinide complexes with N-donor ligands, like Schiff bases and amidinates (Figure 1), to elucidate their complicated electronic properties. The influence of spin-orbit coupling on the chemical bonding in terms of ELI-D2 as well as thermodynamic computations on the stability of the complexes will be presented. In addition, various spectra, such as NMR and IR, acquired from the calculations will be compared with the experimental results to understand the chemical properties of the actinides and predict yet unknown complexes.