Hydrated magnesium cations Mg+(H2O)n, n ≈ 20-60, exhibit chemistry of the hydrated electron in reactions with O 2 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. O ₂ 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 Mg ²⁺. Ion-molecule reactions between Mg⁺(H ₂O)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 Mg ²⁺ is replaced by O₂ ^*- or CO ₂ ^*-. © 2011 American Chemical Society.