Theoretical study of catalytic oxidation cycles of CO with N₂O by Fe⁺ in gas phase

The reaction mechanism between Fe⁺ in the ground state and the excited state with CO and N₂ O has been studied using the density functional theory (DFT) at UB3LYP/6-311 + G (2d) level. The geometries for reactants, the transition states and the products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. For each stationary point, the single-point energy calculations were carried out by UB3LYP/6-311 + + G (3df, 3pd) method. The potential energy curve-crossing diagrams were investigated for the state correlation between quartet and sextet states in the reaction of Fe⁺ with CO and N₂O. The results showed that this reaction is a two-step reaction and the reaction mechanism is an insertion-elimination mechanism. There are two crossing points between the quartet and the sextet potential energy surfaces (PESs), which would effectively reduce the activation energy and play a significant and beneficial role in the kinetic and thermodynamic aspects of this catalytic reaction. (authors)