Reactions of Hydrated Electrons (H2O)n− with Carbon Dioxide and Molecular Oxygen: Hydration of the CO2− and O2− Ions

• Published in: Chemistry : a European journal 2004-10, Vol.10 (19), p.4822-4830
• Main Authors: Balaj, O. Petru, Siu, Chi-Kit, Balteanu, Iulia, Beyer, Martin K., Bondybey, Vladimir E.
• Format: Article
• Language: English
• Subjects: gas-phase reactions; hydrated electrons; nanodroplets; radical ions; solvation
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200400416

The gas‐phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n− because they possess low‐lying empty π* orbitals. The molecular CO2− and O2− anions are concurrently solvated and stabilized by the water ligands to form CO2−(H2O)n and O2−(H2O)n. Core exchange reactions are also observed, in which CO2−(H2O)n is transformed into O2−(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2−(H2O)n clusters are thermodynamically favored with respect to CO2−(H2O)n. Electron detachment from the product species is only observed for CO2−(H2O)2, in agreement with the calculated electron affinities and solvation energies. Both CO2 and O2 can act as electron scavengers and form hydrated molecular anions upon collisions with gas‐phase hydrated electrons. While O2− is a stable anion, stabilization of CO2− is achieved by the presence of solvent molecules; five H2O molecules form a cyclic pentamer with four of them interacting with CO2− (see picture).