Charge-dipole bound anion-anion complexes.

BACKGROUND: At short range, charge-dipole interactions, which scale with R-2, can override the more conceptually familiar charge-charge ones, which scale with R-1. This can lead to metastable minima for complexes between ions of like charge, but also be designed to create, as shown here, thermodynamically stable anion-anion complexes. We show that such complexes can be stable to dissociation into their component anions, and to autoionization. METHODS: Geometries were optimized at the MP2/aug-cc-pVTZ level, and optimized structures confirmed to be minima or transition states by calculating the normal vibrations within the harmonic approximation at this level. Energies were refined using these geometries for CCSD(T) calculations with the same basis set. MP2/aug-cc-pVTZ single points with the complexed chloride ion represented by a point charge were used to demonstrate the charge-dipole nature of the bonding interaction. All calculations used Gaussian16.