Spectroscopy and electronic structures of mono- and binuclear high-valent non-heme iron–oxo systems

High-valent iron–oxo intermediates are known or believed to be key oxidizing species in the catalytic mechanisms of many mononuclear and binuclear non-heme iron enzymes. So far only limited experimental data on their electronic structures are available. In this study we extend knowledge from the experimentally well characterized mononuclear FeIV=O (S = 1) biomimetic model system to computational insight into the spectroscopy and electronic structures of mono-and binuclear high-valent iron–oxo enzyme intermediates. In the mononuclear FeIV=O complexes, we predict the spectroscopy and energies of the electronic transitions to be very different for the S = 1 and S = 2 spin states, but the iron–oxo bonding for both spin states to be very similar. A comparison of the S = 2 mono- and binuclear high-valent iron-sites predicts similar electronic transitions. However, the bent iron–oxo bridge and interactions with the second iron-center in the dimer shift the transitions to higher energies and splits the d(xz/yz) orbital set. These electronic structure and TD-DFT results provide a basis for understanding the spectroscopy and electronic structures of high-valent intermediates in mono- and binuclear non-heme iron enzymes.