On the origin of the different performance of iron and manganese monocations in catalyzing the nitrous oxide reduction by carbon oxide.

The potential energy profiles for the Fe+- and Mn+-assisted reduction of N2O by CO were studied at the B3LYP density functional level in order to get the differences in the reaction mechanisms determining the efficiency of iron and the inactivity of manganese as ionic catalysts. Both ground and excited states of cations were taken into account in view of a possible participation of the highest multiplicities to the reduction process. Results indicated that a spin inversion occurs in the rate-determining step of iron ion-catalyzed reaction that improves the performance of the cation. However, also in the absence of the two-state reactivity phenomenon, contrary to manganese ion, iron is active in catalyzing the reaction.