Study of the catalytic mechanism of a non-heme Fe catalyst: The role of the spin state of the iron

Abstract The oxidative catalytic evolution of a highly efficient non-heme Fe catalyst (LFeIII) was studied using EPR and Low-Temperature UV–Vis spectroscopies. The key transient-intermediates of the Fe center were monitored during the catalytic cycle, in the presence of H2O2. The EPR data show that this non-heme Fe catalyst can evolve via either High-Spin or Low-Spin states of the Fe center, with only the Low-Spin path being catalytically efficient. The key transient, intermediate [LFeIII-OOH] in the Low-Spin path has also been monitored with Low-Temperature UV–Vis. Arrhenius analysis allowed determination of the energy barrier Ea = 18.5 ± 6.2 kJ/mole for the Low-Spin path.