Theoretical study of substitution effect in superalkali OM3 (MÂ =Â Li, Na, K)

•The superalkalies with mixed alkali metal ligands are investigated.•The ionization potentials for the studied OM3 species are lower than that of Cs atom.•The superalkali cations OM3+ exhibit very large HOMO-LUMO gaps of 7.58-10.58 eV.•Replacing the alkali metal ligand with the larger one can decrease the IP of OM3.

A class of superalkalies OM3 (M = Li, Na, K) and their corresponding cations OM3+ were theoretically investigated. The OM3 molecules possess very low adiabatic ionization potentials (AIPs) of 2.842-3.558 eV at the CCSD(T)/6-311+G(3df) level. It was found that the ionization potentials of OM3 depend on the nature of the peripheral ligand atom and can be efficiently decreased upon replacing the M atom with the more electropositive one. Such superalkalies characterized by lower ionization potentials add candidates to the research on superatoms and can be used in the synthesis of new nontraditional salts where strong reducers are involved.

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