US EPA

7424640 

Journal Article 

Vibrational Characterization of Radical Ion Adducts between Imidazole and CO2 

Craig, SM; Johnson, CJ; Ranasinghe, DS; Perera, A; Bartlett, RJ; Berman, MR; Johnson, MA; , 

2018 

1 

Journal of Physical Chemistry A
ISSN: 1089-5639
EISSN: 1520-5215 

AMER CHEMICAL SOC 

WASHINGTON 

122 

15 

3805-3810 

English 

29608067 

10.1021/acs.jpca.8b01883 

WOS:000430783700011 

https://pubs.acs.org/doi/10.1021/acs.jpca.8b01883
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We address the molecular level origins of the dramatic difference in the catalytic mechanisms of CO2 activation by the seemingly similar molecules pyridine (Py) and imidazole (Im). This is accomplished by comparing the fundamental interactions of CO2 radical anions with Py and Im in the isolated, gas phase PyCO2- and ImCO2- complexes. These species are prepared by condensation of the neutral compounds onto a (CO2) n- cluster ion beam by entrainment in a supersonic jet ion source. The structures of the anionic complexes are determined by theoretical analysis of their vibrational spectra, obtained by IR photodissociation of weakly bound CO2 molecules in a photofragmentation mass spectrometer. Although the radical PyCO2- system adopts a carbamate-like configuration corresponding to formation of an N-C covalent bond, the ImCO2- species is revealed to be best described as an ion-molecule complex in which an oxygen atom in the CO2- radical anion is H-bonded to the NH group. Species that feature a covalent N-C interaction in ImCO2- are calculated to be locally stable structures, but are much higher in energy than the largely electrostatically bound ion-molecule complex. These results support the suggestion from solution phase electrochemical studies (Bocarsly et al. ACS Catal. 2012, 2, 1684-1692) that the N atoms are not directly involved in the catalytic activation of CO2 by Im. 

Chemical activation; Condensation reactions; Fighter aircraft; Ion beams; Ion sources; Molecules; Negative ions; Supersonic aerodynamics; Catalytic activation; Catalytic mechanisms; Cluster ion beams; Electrochemical studies; Ion-molecule complexes; Neutral compounds; Photofragmentation; Stable structures; Carbon dioxide