Ab initio insights into hydrogen-rich polynuclear non-metallic superalkali cations

Superalkalis are defined as the species having lower ionisation energies (IEs) than alkali atoms or the cations having lower electron affinities than alkali cations. Typical examples include FLi₂ ⁺, OLi₃ ⁺, NLi₄ ⁺, etc., which can be represented by the general formula of XM _k+1, where X is a central electronegative atom of valency k, and M represents alkali metal ligands. Enormous progress has been made in the research and development of novel superalkalis due to their various applications, including as strong reducers. However, most of the superalkali cations (except a few) reported, thus far, are decorated with alkali metal atoms. Later, binuclear non-metallic superalkali cations were reported in which the role of alkali atoms was played by hydrogen atoms. This led to an inquiry into whether it is possible to reduce the, IE of H-based superalkali species further by increasing the chain, i.e., going from binuclear to polynuclear species. We have performed a series of works in this direction using state-of-the-art computational methods. In addition, hydrogen-based organic superalkalis have also been reported. The present account focuses on some interesting findings of these works and their implication for future directions.