title: The kinetic isotope effect as a probe of spin crossover in the C-H activation of methane by the FeO(+) cation.
abstract: Two-state reactivity (TSR) is often used to explain the reaction of transition-metal-oxo reagents in the bare form or in the complex form. The evidence of the TSR model typically comes from quantum-mechanical calculations for energy profiles with a spin crossover in the rate-limiting step. To prove the TSR concept, kinetic profiles for CH activation by the FeO(+) cation were explored. A direct dynamics approach was used to generate potential energy surfaces of the sextet and quartet H-transfers and rate constants and kinetic isotope effects (KIEs) were calculated using variational transition-state theory including multidimensional tunneling. The minimum energy crossing point with very large spin-orbit coupling matrix element was very close to the intrinsic reaction paths of both sextet and quartet H-transfers. Excellent agreement with experiments were obtained when the sextet reactant and quartet transition state were used with a spin crossover, which strongly support the TSR model.
authors: Department of Applied Chemistry and Institute of Applied Sciences, Kyung Hee University, Yongin-Si, Gyeonggi-Do, 446-701 (Korea).
authors: Binh Khanh
authors: BK
authors: Mai
authors: Yongho
authors: Y
authors: Kim
keywords: hydrogen atom transfer; kinetic isotope effect; spin crossover; two-state reactivity; variational transition-state theory