Infrared Multiple Photon Dissociation Spectroscopy of Hydrated Cobalt Anions Doped with Carbon Dioxide CoCO(2)(H(2)O)(n) (−), n=1–10, in the C−O Stretch Region

We investigate anionic [Co,CO(2),nH(2)O](−) clusters as model systems for the electrochemical activation of CO(2) by infrared multiple photon dissociation (IRMPD) spectroscopy in the range of 1250–2234 cm(−1) using an FT‐ICR mass spectrometer. We show that both CO(2) and H(2)O are activated in a significant fraction of the [Co,CO(2),H(2)O](−) clusters since it dissociates by CO loss, and the IR spectrum exhibits the characteristic C−O stretching frequency. About 25 % of the ion population can be dissociated by pumping the C−O stretching mode. With the help of quantum chemical calculations, we assign the structure of this ion as Co(CO)(OH)(2) (−). However, calculations find Co(HCOO)(OH)(−) as the global minimum, which is stable against IRMPD under the conditions of our experiment. Weak features around 1590–1730 cm(−1) are most likely due to higher lying isomers of the composition Co(HOCO)(OH)(−). Upon additional hydration, all species [Co,CO(2),nH(2)O](−), n≥2, undergo IRMPD through loss of H(2)O molecules as a relatively weakly bound messenger. The main spectral features are the C−O stretching mode of the CO ligand around 1900 cm(−1), the water bending mode mixed with the antisymmetric C−O stretching mode of the HCOO(−) ligand around 1580–1730 cm(−1), and the symmetric C−O stretching mode of the HCOO(−) ligand around 1300 cm(−1). A weak feature above 2000 cm(−1) is assigned to water combination bands. The spectral assignment clearly indicates the presence of at least two distinct isomers for n ≥2.