Spectroscopic and quantum chemical studies on low-spin Fe-IV=O complexes: Fe-O bonding and its contributions to reactivity
Cited 102 times inCited 102 times in
- Spectroscopic and quantum chemical studies on low-spin Fe-IV=O complexes: Fe-O bonding and its contributions to reactivity
- Decker, Andrea; Rohde, Jan-Uwe; Klinker, Eric J.; Wong, Shaun D.; Que, Lawrence, Jr.; Solomon, Edward I.
- Issue Date
- AMER CHEMICAL SOC
- JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, v.129, no.51, pp.15983 - 15996
- High-valent Fe-IV=O species are key intermediates in the catalytic cycles of many mononuclear non-heme iron enzymes and have been structurally defined in model systems. Variable-temperature magnetic circular dichroism (VT-MCD) spectroscopy has been used to evaluate the electronic structures and in particular the Fe-O bonds of three Fe-IV=O (S = 1) model complexes, [Fe-IV(O)(TMC)(NCMe)](2+), [Fe-IV(O)(TMC)(OC(O)CF3)](+), and [Fe-IV(O)(N4py)](2+). These complexes are characterized by their strong and covalent Fe-O pi-bonds. The MCD spectra show a vibronic progression in the nonbonding -> pi(*) excited state, providing the Fe-O stretching frequency and the Fe-O bond length in this excited state and quantifying the pi-contribution to the total Fe-O bond. Correlation of these experimental data to reactivity shows that the [Fe-IV(O)(N4py)](2+) complex, with the highest reactivity toward hydrogen-atom abstraction among the three, has the strongest Fe-O pi-bond. Density functional calculations were correlated to the data and support the experimental analysis. The strength and covalency of the Fe-O pi-bond result in high oxygen character in the important frontier molecular orbitals (FMOs) for this reaction, the unoccupied beta-spin d(xz/yz) orbitals, that activates these for electrophilic attack. An extension to biologically relevant Fe-IV=O (S = 2) enzyme intermediates shows that these can perform electrophilic attack reactions along the same mechanistic pathway (pi-FMO pathway) with similar reactivity but also have an additional reaction channel involving the unoccupied alpha-spin d(z(2)) orbital (sigma-FMO pathway). These studies experimentally probe the FMOs involved in the reactivity of Fe-IV=O (S = 1) model complexes resulting in a detailed understanding of the Fe-O bond and its contributions to reactivity
- Appears in Collections:
- CHM_Journal Papers
- Files in This Item:
- There are no files associated with this item.
can give you direct access to the published full text of this article. (UNISTARs only)
Show full item record
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.