Two-state reaction mechanism of Ni₂⁺ with c-C₆H₁₂ on the quartet and doublet potential energy surfaces has been investigated at the B3LYP level. As a result, the ground state for reactants is doublet state, for products is quartet state. A further study on different potential energy surfaces indicates that the title reaction contains four potential energy surfaces crossing in doublet and quartet state, which occurs during the first hydrogen migration step (⁴IM1→⁴TS1/2), the third hydrogen migration step (⁴TS15/16→⁴IM15) and flip step (⁴IM5→⁴TS5/6, ²TS11/12→²IM12), respectively. The first, second and third potential energy surfaces crossing are the transitions of quartet to doublet state, and the last one is doublet to quartet state. Using single-point energy calculations based on IRC of the different states to locate the approximate structure of crossing points (CPs) between potential energy surfaces, and more accurate structure of CPs, minimal energy crossing points (MECPs), have been obtained by the Crossing 2004 procedure. The spin-orbit coupling (SOC) constant was calculated to discuss the possible spin inversion processes. The values of SOC constants near the MECP1～MECP4 were calculated to be 318.01, 396.89, 268.74 and 306.67 cm^-1, respectively, the large values of SOC constants indicate the transition from one potential energy surface to another proceeding smoothly and reducing the barrier of reaction in large extent. Based on the result of our calculation, the reaction contains two different channels, one face dehydrogenation and different face dehydrogenation, the first one is confirmed as the dominant channel due to the large exothermicity. Flip process, the critical factor leading to the different face dehydrogenation, has a large barrier of 33 kcal/mol in rate limiting step (²IM9→²TS9/10→²IM10) leading to a few different face dehydrogenation products. Our calculation can well explain the experiment observation.

Key words: density functional theory, spin-orbit coupling, reaction mechanism, potential energy surfaces