Carbon Dioxide Activation by Surface Excess Electrons. An EPR Study of the CO2- Radical Ion Adsorbed on the Surface of MgO

The CO2- radical anion has been generated at the surface of MgO by direct electron transfer from surface trapped excess electrons and characterized by electron paramagnetic resonance spectroscopy. Both C-13 and O-17 hyperfine structures have been resolved for the first time, leading to a detailed mapping of the unpaired electron spin density distribution over the entire radical anion. The magnetic equivalence of the two O nuclei has been ascertained allowing a side-on a sorption structure at low-coordinate Mg2+ ions to be proposed for the surface stabilized radical.