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Infrared Multiple Photon Dissociation Spectroscopy of Hydrated Cobalt Anions Doped with Carbon Dioxide CoCO₂ (H₂ O)_n ^- , n=1-10, in the C-O Stretch Region.

ABSTRACT: We investigate anionic [Co,CO₂ ,nH₂ O]^- 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 H₂ O are activated in a significant fraction of the [Co,CO₂ ,H₂ 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,CO₂ ,nH₂ O]^- , n≥2, undergo IRMPD through loss of H₂ 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.

SUBMITTER: Barwa E

PROVIDER: S-EPMC7051846 | biostudies-literature |

REPOSITORIES: biostudies-literature

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