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
Wiley -- Chemistry – A European Journal
DOI 10.1002/chem.201904182
Keyword(s)
  1. activation
  2. carbon dioxide
  3. catalysis
  4. cobalt
  5. IR spectroscopy
Abstract(s)

Abstract

We investigate anionic [Co,CO2,nH2O] clusters as model systems for the electrochemical activation of CO2 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 CO2 and H2O are activated in a significant fraction of the [Co,CO2,H2O] 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,CO2,nH2O], n≥2, undergo IRMPD through loss of H2O 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.