Cation-cation interactions (CCIs) have been widely studied due to their relevance in pentavalent actinide chemistry. Recently, the second structure containing a side-on [NpVO2-NpVO2]2+ CCI was isolated in the Burns group. Side-on neptunyl interactions have remarkably short Np-Np distances resulting in coupling between NpV centers. While crystallization of CCIs provides snapshots into the interaction, theory can further explain the complex electronic structure. Models of the two experimental structures were optimized at the density functional level followed by bond order analysis.  Subsequent high-level wavefunction based methods were used when feasible. Complete active space self-consistent field (CASSCF) with second order perturbation theory (CASPT2) calculations and generalized active space self-consistent field (GASSCF) calculations indicate degenerate singlet, triplet, and quintet spin states. Spin-orbit effects were included with the complete active space state interaction (CASSI) approach and a potential energy surface was determined connecting the side-on CCI structure to the more common end-on CCI structure.

Nature of the side-on neptunyl cation-cation interaction

243rd National Meeting (2012)

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