Samuel Wilson
X-ray Absorption Spectroscopy (XAS) has been used extensively to probe both the electronic and geometric structure of metal sites. The technique is element specific, meaning that it can be used to probe the electronic transitions of metal sites rather than those due to ligands or the surrounding environment. XAS can be applied to several types of studies including K-edge, L-edge and EXAFS (Extended X-ray Absorption Fine Structure). Metal L-edge spectroscopy specifically probes the unoccupied metal d-orbitals looking at 2p-to-3d transitions that are dipole-allowed.
Most L-edge spectra are currently collected at the Stanford Synchrotron Radiation Laboratory (SSRL) in the solid phase under ultra-high vacuum and at high concentrations. Spectroscopic results are then analyzed by computational methods such as DFT and various multiplet simulations.
New spectroscopic techniques are also currently under development to allow for the study of samples in either the liquid phase or under normal atmosphere as complexes which contain bound dioxygen decompose under UHV.
The overall goal of the project is to further scientific understanding of iron bonding in heme vs. non-heme systems, thereby refining the current L-edge methodology and providing important insights into the electronic structure, reactivity, and chemical bonding of various families of iron enzymes and model complexes.
Supervisors: Edward I. Solomon, Keith O. Hodgson, and Britt Hedman
Most L-edge spectra are currently collected at the Stanford Synchrotron Radiation Laboratory (SSRL) in the solid phase under ultra-high vacuum and at high concentrations. Spectroscopic results are then analyzed by computational methods such as DFT and various multiplet simulations.
New spectroscopic techniques are also currently under development to allow for the study of samples in either the liquid phase or under normal atmosphere as complexes which contain bound dioxygen decompose under UHV.
The overall goal of the project is to further scientific understanding of iron bonding in heme vs. non-heme systems, thereby refining the current L-edge methodology and providing important insights into the electronic structure, reactivity, and chemical bonding of various families of iron enzymes and model complexes.
Supervisors: Edward I. Solomon, Keith O. Hodgson, and Britt Hedman
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Papers by Samuel Wilson
Here we report the high-resolution crystal structure of a mononuclear non-heme side-on iron(III)-peroxo complex, [Fe(III)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(III)-peroxo complex is cleanly converted to the iron(III)-hydroperoxo complex, [Fe(III)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(III)-hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(III)-hydroperoxo species.
All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)-hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)-oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)-hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes."
Here we report the high-resolution crystal structure of a mononuclear non-heme side-on iron(III)-peroxo complex, [Fe(III)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(III)-peroxo complex is cleanly converted to the iron(III)-hydroperoxo complex, [Fe(III)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(III)-hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(III)-hydroperoxo species.
All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)-hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)-oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)-hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes."