Electronic Structure and Bonding in Molecular f Element Chemistry

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For calculations on molecules containing f-elements, relativistic effects must be explicitly included in calculations and the near-degeneracy of many valence atomic orbitals results in many closely-spaced electronic states. These complications necessitate the use of ab initio wave functional theory (WFT) to obtain a detailed understanding of the electronic structure of f-element containing molecules.The first focus of the project is on molecules of the general formula EAnF3, where E = N, P, As, Sb and Bi; and An = U, Np, and Pu. Previous calculations suggest that NUF3, NNpF3 and NPuF3 have triple An-N bonds; however other electronic states (corresponding to the unpairing of electrons in the triple bond) are computed to be very close in energy. These excited states may match better with the experimental vibrational spectroscopy of these molecules [Inorg. Chem. 48 (2009) 6594], and so the true electronic structure is not clear. Initial DFT calculations present a seemingly clear picture for EUF3; increasing multiplicity down group 15 (N: singlet; P, As: triplet; Sb, Bi: quintet), with a bond order of ~1 for all but NUF3 (with a bond order of 3). This does not reflect existing literature which predicts singlet, triple-bonded structures for PUF3 and AsUF3 [Inorg. Chem. 48 (2009) 6594]. Ab initio calculations will be employed to explore this discrepancy.The initial DFT calculations present a considerably less clear picture for ENpF3 and EPuF3, where spin contamination is very large for low multiplicities. Open-shell electronic ground states are challenging to calculate with DFT, so WFT techniques will be employed to be able to describe their structures.