Hydrated Magnesium Cations Mg⁺(H₂O)_n, n ≈ 20–60, Exhibit Chemistry of the Hydrated Electron in Reactions with O₂ and CO₂

Ion–molecule reactions of Mg⁺(H₂O)_n, n ≈ 20–60, with O₂ and CO₂ are studied by Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. O₂ and CO₂ are taken up by the clusters. Both reactions correspond to the chemistry of hydrated electrons (H₂O)_n^–. Density functional theory calculations predicted that the solvation structures of Mg⁺(H₂O)₁₆ contain a hydrated electron that is solvated remotely from a hexa-coordinated Mg²⁺. Ion–molecule reactions between Mg⁺(H₂O)₁₆ and O₂ or CO₂ are calculated to be highly exothermic. Initially, a solvent-separated ion pair is formed, with the hexa-coordinated Mg²⁺ ionic core being well separated from the O₂^•– or CO₂^•–. Rearrangements of the solvation structure are possible and produce a contact-ion pair in which one water molecule in the first solvation shell of Mg²⁺ is replaced by O₂^•– or CO₂^•–.