Infrared Spectroscopy of Size‐Selected Hydrated Carbon Dioxide Radical Anions CO(2) (.−)(H(2)O)(n) (n=2–61) in the C−O Stretch Region

Understanding the intrinsic properties of the hydrated carbon dioxide radical anions CO(2) (.−)(H(2)O)(n) is relevant for electrochemical carbon dioxide functionalization. CO(2) (.−)(H(2)O)(n) (n=2–61) is investigated by using infrared action spectroscopy in the 1150–2220 cm(−1) region in an ICR (ion cyclotron resonance) cell cooled to T=80 K. The spectra show an absorption band around 1280 cm(−1), which is assigned to the symmetric C−O stretching vibration ν (s). It blueshifts with increasing cluster size, reaching the bulk value, within the experimental linewidth, for n=20. The antisymmetric C−O vibration ν (as) is strongly coupled with the water bending mode ν (2), causing a broad feature at approximately 1650 cm(−1). For larger clusters, an additional broad and weak band appears above 1900 cm(−1) similar to bulk water, which is assigned to a combination band of water bending and libration modes. Quantum chemical calculations provide insight into the interaction of CO(2) (.−) with the hydrogen‐bonding network.