Figure 14.
Relevant FMOs for 1b and the transition state-like strained structure (TS’) along the PES (denoted by the green star on Figure 13) calculated at the level of BP86 mixed with 10% Hartree-Fock exchange, using the 6–311G* basis set on Fe-O2 and 6–31G* on the remaining atoms. 1b has an α unoccupied FMO with primarily semiquinone character (upper-left). As the substrate approaches the peroxo, this unoccupied FMO gains some peroxo π*v character, as shown in the α LUMO on the right. The peroxo π*v orbital is occupied in 1b, as shown in the bottom left; this reaction is thus a nucleophilic attack.