New insights into the two catalyst cycles of the Pt+-catalyzed oxidation of methane by oxygen: Spin–orbit coupling, spin-inversion probabilities, and kinetic information

Gas-phase Pt+-catalyzed oxidation of methane by oxygen includes two important and interested cycle reactions. They have been theoretically investigated using density functional theory (DFT) at B3LYP/6-311+G (3df, 3pd) level on their doublet and quartet potential energy surfaces (PESs). Three crossing points between the two potential energy surfaces are located. The possible spin inversion processes are estimated by means of spin–orbit coupling (SOC) calculations. The probability of electronic transition in the vicinity of the minimum energy crossing point (MECP) was treated with Landau–Zener-type theory. Finally, the minimum energy reaction paths were found. The energetic span (δE) model proposed by Kozuch has been applied to reveal the kinetic behavior of the two catalytic cycles. Some other theoretical analyses have been done using natural bonding orbital (NBO) and molecular orbital theory.