Spin-Forbidden Reactions: Adiabatic Transition States Using Spin–Orbit Coupled Density Functional Theory

Carlo Alberto Gaggioli, Leonardo Belpassi, Francesco Tarantelli, Jeremy N. Harvey, Paola Belanzoni

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

A spin-forbidden chemical reaction involves a change in the total electronic spin state from reactants to products. The mechanistic study is challenging because such a reaction does not occur on a single diabatic potential energy surface (PES), but rather on two (or multiple) spin diabatic PESs. One possible approach is to calculate the so-called “minimum energy crossing point” (MECP) between the diabatic PESs, which however is not a stationary point. Inclusion of spin–orbit coupling between spin states (SOC approach) allows the reaction to occur on a single adiabatic PES, in which a transition state (TS SOC) as well as activation free energy can be calculated. This Concept article summarizes a previously published application in which, for the first time, the SOC effects, using spin–orbit ZORA Hamiltonian within density functional theory (DFT) framework, are included and account for the mechanism of a spin-forbidden reaction in gold chemistry. The merits of the MECP and TS SOC approaches and the accuracy of the results are compared, considering both our recent calculations on molecular oxygen addition to gold(I)-hydride complexes and new calculations for the prototype spin-forbidden N2O and N2Se dissociation reactions.

Original languageEnglish (US)
Pages (from-to)5006-5015
Number of pages10
JournalChemistry - A European Journal
Volume24
Issue number20
DOIs
StatePublished - Apr 6 2018

Keywords

  • adiabatic transition states
  • density functional theory
  • minimum energy crossing point
  • spin-forbidden reactions
  • spin-orbit

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