Formation of [(CO2)nCH3I]− anions in the reaction of (CO2)N− with CH3I

The reactions of negatively charged clusters of carbon dioxide, (CO2)N− (N ≥ 3), with CH3I were used to form [(CO2)nCH3I]−. The observed product distribution showed a distinct bimodal behavior; the mass spectrum of the product anions consisted of [(CO2)nCH3I]− with n = 1–3 and n ≥ 7, while those with n = 4, 5 and 6 were not detected. Photoelectron spectra of the product anions revealed that [(CO2)nCH3I]− with n = 1–3 possess an anionic core of [(CO2)CH3I]−, while the larger cluster anions (n ≥ 7) have an electronic structure represented as [(CO2)n− … CH3I]. The vertical detachment energy of [(CO2)CH3I]− is estimated to be > 3.25 eV, indicating a delocalization of the excess electron in [(CO2)CH3I]−.