Transition states of spin-forbidden reactions. Issue 6 (22nd January 2018)

• Record Type: Journal Article
• Authors: Yang, Bo; Gagliardi, Laura; Truhlar, Donald G.
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 6(2018)
• Page Start: 4129
• Page End: 4136
• Publication Date: 2018-01-22
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp07227a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : New approximation method for locating stationary points on lowest spin-coupled potential energy surface (PES) using density functional calculations. Abstract : Spin–orbit coupling plays an important role in determining the mechanisms and kinetics of spin-forbidden reactions and many reactions exhibiting two-state reactivity. Spin–orbit coupling can allow the system to change its spin state, especially when potential energy surfaces (PESs) of two spin states approach each other. Here, we introduce a convenient new approximation method for locating stationary points on the lowest mixed-spin potential energy surface along a reaction pathway by using density functional calculations. The mixing of different spin states is achieved by introducing the spin–orbit coupling into the electronic Hamiltonian using a pre-defined coupling constant. Two examples are given using the new methodology: (a) a CO association reaction with the coordinatively unsaturated Fe(CO)4 complex and (b) an α-H elimination reaction of a model complex containing W. We computed a Gibbs free energy of activation of 2.8 kcal mol −1 for the CO association reaction, which is reasonably consistent with the experimentally measured reaction rate. For the H elimination reaction, the spin change occurs at a relatively low energy, and the present treatment allows one conclude that kinetics of the reaction can be reasonably well described without spin–orbit coupling.