Two-state reactivity in the acetylene cyclotrimerization reaction catalyzed by a single atomic transition-metal ion: The case for V+ and Fe+

Recent experimental and theoretical studies have focused on the cyclotrimerization reaction of acetylene to form benzene catalyzed by a single atom; however, the mechanism of this process remains unclear. In this work, we theoretically studied the atomic-level mechanisms of the acetylene cyclotrimerization reactions catalyzed by V+ and Fe+ using the automated reaction path search calculation, which can consider spin state change. In both cases, the spin state change could occur during the course of the reaction. We also discuss the efficiency of the spin state transition by calculating spin-orbit coupling constants.