The interaction of negative charge with carbon dioxide – insight into solvation, speciation and reductive activation from cluster studies

The interaction of CO2 with negative charge is of high importance in many natural and industrial processes, since reductive activation is one of the most common and convenient ways to chemically unlock this robust molecule. While free CO2 does not form stable anions, the accessibility of low-lying molecular orbitals is critical for its chemical versatility and allows CO2 to act as solvent as well as a reaction partner for negative ions. Experiments on mass selected cluster ions are highly suitable for the study of the fundamental properties of CO2 and its interaction with excess electrons and anions, since they circumvent many problems associated with experiments in the condensed phase. The combination of mass spectrometry, laser spectroscopy and quantum chemical calculations results in a powerful tool set to address questions of reactivity, ion speciation and solvation, and they can provide key information to understanding the ion chemistry of CO2.