The nature of anionic alkali metals (alkalides) in solution is traditionally thought to be a noninteracting and isolated solute. However, we have found that the true picture for an alkalide solute is an ion pairing one between the alkalide and a complexed cationic alkali metal (superalkali), creating a less electronegative species for alkalide ion pairing purposes. Both experimental and computational DFT results support and display superalkali-alkalide ion pairing, with the experimental data obtained with concentration dependent ionic conductivity, dielectric spectroscopy, and neutron scattering. The DFT calculated binding energies show a clear preference for ion pairing and that the ion pair is partially covalent in the superalkali-alkalide models. The NMR results display that the system is thermally activated and reversible. The structure that can explain all of the obtained results is a structure with an ion paired alkalide instead of an unperturbed alkalide.

Superalkali−alkalide interactions and ion pairing in low-polarity solvents

ACS Spring 2022

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