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Spin‐Forbidden Reactions: Adiabatic Transition States Using Spin–Orbit Coupled Density Functional Theory
Author(s) -
Gaggioli Carlo Alberto,
Belpassi Leonardo,
Tarantelli Francesco,
Harvey Jeremy N.,
Belanzoni Paola
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704608
Subject(s) - adiabatic process , spin (aerodynamics) , physics , density functional theory , orbit (dynamics) , atomic physics , condensed matter physics , functional theory , quantum mechanics , thermodynamics , engineering , aerospace engineering
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 N 2 O and N 2 Se dissociation reactions.