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 inononuclear 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 Fe-IV=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 Fe-IV=0 complexes, we predict the spectroscopy and energies of the electronic transitions to be very different for the S = I 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-7) 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. (c) 2006 Elsevier Inc. All rights reserved.