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Key research themes
1. What factors govern O-O bond cleavage mechanisms in ferric-hydroperoxo complexes and how do ligand environments modulate this process?
This research theme focuses on understanding the electronic, structural, and ligand field parameters controlling O-O bond cleavage in ferric-hydroperoxo species, which are pivotal intermediates in many iron-dependent biological oxidations. The investigations seek to elucidate how covalency, ligand charge, spin states, and iron d orbital interactions influence O-O bond weakening and cleavage pathways. This has fundamental implications for the mechanism of enzymatic oxygen activation and biomimetic catalyst design.
Key finding: Density functional theory (DFT) studies on multiple octahedral ferric-hydroperoxo complexes with varying ratios of hydroxide and water ligands demonstrate that increasing ligand charge and covalence intensify O-O bond... Read more
Key finding: DFT calculations on Rieske dioxygenase (RDO) models predict that dioxygen initially binds as a high-spin S=2 side-on ferric-superoxo intermediate, which upon one-electron reduction yields a ferric-peroxo species (S=5/2 or... Read more
Key finding: Contrary to previous assumptions, DFT calculations reveal that in a non-heme ferric-oxo complex, Fe(III)-oxo bonding includes significant π interactions, contrary to the prior belief that π bonding is absent and substituted... Read more
2. How do electronic structure and covalency considerations redefine the oxidation states and bonding descriptions in high-valent iron-oxo species?
This theme addresses the fundamental electronic description of high-valent iron-oxo species, challenging classical assignments of iron oxidation states as Fe(IV) or Fe(V). Research employs advanced quantum chemical methods to assess the covalent character of Fe–O bonds, spin densities, and the localization of unpaired electrons to provide alternative viewpoints on electronic structures. These insights influence interpretations of reactivity and catalytic mechanisms in heme and non-heme iron enzymes.
Key finding: Unrestricted MP2 calculations on octahedral S=1 [FeO]2+ complexes reveal that the degree of Fe–O covalence is lower than previously estimated by DFT and RHF methods, supporting a description closer to an Fe(III)–oxo radical... Read more
Key finding: DFT calculations demonstrate the feasibility of a novel catalase mechanism wherein the catalytic "Compound I" intermediate, formally Fe(V)=O, reacts with H2O2 through oxygen atom substitution forming a Fe(V)-peroxo... Read more
Key finding: Mössbauer and inelastic nuclear resonant X-ray scattering data provide precise iron isotope fractionation factors correlated with iron oxidation state and local bonding environment. Ferric iron compounds exhibit higher iron... Read more
3. What roles do ligand coordination, cluster nuclearity, and substitution influence the structure and magnetic properties of high-valent iron intermediates?
This theme investigates how ligand types (e.g., Schiff bases, oximes), nuclearity of iron clusters, halide coordination, and substitution patterns dictate the cluster structures, symmetry, oxidation states, and magnetic exchange interactions of iron-containing intermediates. These structural and electronic variables profoundly affect reactivity and the electronic communication within multinuclear iron assemblies relevant to catalysis and enzymatic mimics.
Key finding: Synthesis and X-ray crystallography of mixed halide [Fe4S4XnY4−n]2− clusters reveal systematic symmetry reduction from idealized Td to lower point groups depending on halide substitution. Mössbauer spectroscopy confirms full... Read more
Key finding: The study reports synthesis and magnetic characterization of iron(III)-oxo clusters featuring stacked butterfly {Fe4(μ3-O)2} units, extended by additional Fe and heterometal (Ca2+, La3+) atoms. Magnetic susceptibility and... Read more
Key finding: Selective synthesis of tetranuclear iron(III) clusters with a {Fe4(μ3-O)2} butterfly core is achieved by modulating substituents on Schiff base ligands. Structural and magnetic characterizations show substituent-dependent... Read more