Ab Initio Study of Quantum State-Mediated 3d Transition Metal Ion-Molecule Reactions
DescriptionTransition metal cations play a central role in many research fields, particularly in catalysis and organometallic chemistry. The ability of atomic transition metal cations to mediate the activation of selected chemical bonds is one of their distinct features for allowing the observation of specic chemical outcomes. The transition metal ion has partially filled d or f orbitals and the interactions between valence electrons and orbitals play an important role in its chemical reactivity. The spin-orbit (SO) interactions give rise to dense manifolds of low-lying electronic states and of various spin multiplicities, making the fundamental understanding of chemical reactivity of transition metal cations difficult. Practical catalytic processes occur mostly in condensed phases and solvated medium, however, chemical dynamics and kinetics studies of gas phase reactions involving transition metal ion and simple molecules such as CO2, H2 and CH4 provide an unambiguous insight to chemical reactivity of the idealized catalytic model without the influence of solvent, substrate and ligands.To unravel the complex chemistry of transition metal cations, it is important to investigate reaction mechanism by mapping out the landscape of potential energy surface (PES) from reactant molecules to reaction products, with emphasis relevant reaction energetics and activation barrier heights. Under the Born-Oppenheimer (BO) approximation, the electronic conguration of a molecule largely governs its geometry. In other words, changing the quantum electronic state, by altering the electron spin angular momenta (S), orbital angular momentum (L), and total SO angular momentum (J) of a transition metal ion should have a significant effect on its chemical reactivity. In the circumstances when the BO approximation fails due to the rapid change of adiabatic electronic configuration with nuclear coordinates, chemical reaction no longer occurs on a single PES but must evolve between two or more PESs, giving rise to nonadiabatic effect. The nonadiabatic effect is even more significant in the region near the PES’s crossing such as conical intersection or avoided crossing.In this proposal, we investigate the reaction dynamics of CO2, H2, and CH4 activation mediated by quantum state-selected 3d transition metal ions. We study the nonadiabatic effect on the dynamics of the reactions, especially at the conical intersection or avoided crossing on PES, and how the nonadiabatic effect and SO coupling enhance or inhibit the chemical reactivity.
|Effective start/end date||1/01/21 → …|