INOR 689 |
| Recently we have reported an authentic example of dioxygen activation by iron (III) complexes of TetraAmido Macrocyclic Ligands (TAML) in non-coordinating solvents leading to the formation of stable yet catalytically active oxo-bridged dimeric Fe(IV)-TAML species. To understand the mechanism of this oxygen activation process, electronic and structural properties of these complexes have been studied in detail using Mössbauer spectroscopy and density functional theory (DFT). Using B3LYP functional and 6-311G basis set, we have been able to model the significant structural features (e.g. Fe-Neq and Fe-O bond lengths, out-of-plane shift of iron center, Fe-O-Fe angle) and electronic properties (e.g. spin densities, Mulliken charges) of the Fe(III) and Fe(IV) complexes. The well isolated intermediate spin state (S=3/2) of the Fe(III)-TAML complexes is explained by the anti-bonding nature of the dx2-y2 orbital of Fe(III) which originates from the strong σ-donating capacity of the four deprotonated amide nitrogens. Our DFT calculations provide an estimation of the antiferromagnetic coupling constant between the iron centers in the oxo-bridged dimeric Fe(IV) species. A mechanistic pathway for oxygen activation by Fe-TAMLs is also proposed. |
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General
7:00 PM-10:00 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster
Division of Inorganic Chemistry |