title: Post-Transition State Dynamics in Gas Phase Reactivity: Importance of Bifurcations and Rotational Activation.
abstract: Beyond the established use of thermodynamic vs kinetic control to explain chemical reaction selectivity, the concept of bifurcations on a potential energy surface (PES) is proving to be of pivotal importance with regard to selectivity. In this article, we studied by means of post-transition state (TS) direct dynamics simulations the effect that vibrational and rotational excitation at the TS may have on selectivity on a bifurcating PES. With this aim, we studied the post-TS unimolecular reactivity of the [Ca(formamide)](2+) ion, for which Coulomb explosion and neutral loss reactions compete. The PES exhibits different kinds of nonintrinsic reaction coordinate (IRC) dynamics, among them PES bifurcations, which direct the trajectories to multiple reaction paths after passing the TS. Direct dynamics simulations were used to distinguish between the bifurcation non-IRC dynamics and non-IRC dynamics arising from atomistic motions directing the trajectories away from the IRC. Overall, we corroborated the idea that kinetic selectivity often does not reduce to a simple choice between paths with different barrier heights and instead dynamical behavior after passing the TS may be crucial. Importantly, rotational excitation may play a pivotal role on the reaction selectivity favoring nonthermodynamic products.
authors.affiliation: Departamento de Química, Facultad de Ciencias, Módulo 13, Universidad Autónoma de Madrid , Campus de Excelencia UAM-CSIC, Cantoblanco, E-28049 Madrid, Spain.|Université d'Evry Val d'Essonne , UMR 8587 LAMBE, Boulevard F. Mitterrand, 91025 Evry Cedex, France.|CNRS, Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement , UMR 8587, F-91025 Evry Cedex, France.
authors.forename: Ana
authors.initials: A
authors.lastname: Martín-Sómer
authors.affiliation: Departamento de Química, Facultad de Ciencias, Módulo 13, Universidad Autónoma de Madrid , Campus de Excelencia UAM-CSIC, Cantoblanco, E-28049 Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Yáñez
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States.
authors.forename: William L
authors.initials: WL
authors.lastname: Hase
authors.affiliation: Université d'Evry Val d'Essonne , UMR 8587 LAMBE, Boulevard F. Mitterrand, 91025 Evry Cedex, France.|CNRS, Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement , UMR 8587, F-91025 Evry Cedex, France.|Institut Universitaire de France (IUF) , 103 Blvd. St. Michel, 75005 Paris, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Gaigeot
authors.affiliation: Université d'Evry Val d'Essonne , UMR 8587 LAMBE, Boulevard F. Mitterrand, 91025 Evry Cedex, France.|CNRS, Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement , UMR 8587, F-91025 Evry Cedex, France.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Spezia