The hybrid B3LYP density functional method together with cluster models hav
e been used to explore the adsorption and adsorption-induced dimerization a
nd trimerization of CO over the low-coordinated oxygen anions of MgO solid.
The calculations reveal the following: (i) monomeric, dimeric, and trimeri
c adsorptions on the low-coordinated anions lead to the formation of anioni
c surface species CmOm+12- (m = 1-3); (ii) dioxoketene ion C2O32- Which has
a strong C=C bond can be formed at O-3C site, whereas at O-4C site the for
mation of tripler trans-C2O32- adspecies is thermodynamically favorable ove
r the formation of singlet C2O32- adspecies which has a weak C-C bond; (iii
) The C3O42- surface species does have a ketenic group, i.e., O=C=C <, and
shows substantial stability. The calculated energetics suggests that the di
meric adspecies are unlikely to be stable adspecies, but may be the interme
diates for the formation of higher oligomeric adspecies of CO. The calculat
ed IR frequencies of CmOm+12- (m = 1-3) surface complexes have been compare
d with the experimental IR spectra.