Superoxide Oxidation by a Thiolate-Ligated Iron Complex and Anion Inhibition
| Autor: | Julie A. Kovacs, Maksym A. Dedushko, Jessica H Pikul |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Anions
Coordination sphere Absorption spectroscopy Molecular Conformation Disproportionation 010402 general chemistry Ferric Compounds 01 natural sciences Medicinal chemistry Article Inorganic Chemistry Superoxide dismutase chemistry.chemical_compound Superoxides Sulfhydryl Compounds Physical and Theoretical Chemistry biology 010405 organic chemistry Superoxide Hydrogen-Ion Concentration Antibonding molecular orbital 0104 chemical sciences Oxygen Unpaired electron chemistry Superoxide reductase biology.protein Oxidation-Reduction |
| Zdroj: | Inorg Chem |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/acs.inorgchem.1c00336 |
| Popis: | Superoxide (O(2)(•−)) is a toxic radical, generated via the adventitious reduction of dioxygen (O(2)), which has been implicated in a number of human disease states. Nonheme iron enzymes, superoxide reductase (SOR) and superoxide dismutase (SOD), detoxify O(2)(•−) via reduction to afford H(2)O(2) and disproportionation to afford O(2) and H(2)O(2), respectively. The former contains a thiolate in the coordination sphere, which has been proposed to prevent O(2)(•−) oxidation to O(2). The work described herein shows that, in contrast to this, oxidized thiolate-ligated [Fe(III)(S(Me2)N(4)(tren)(THF)](2+) (1(ox)-THF) is capable of oxidizing O(2)(•−) to O(2). Coordinating anions, Cl(−) and OAc(−), are shown to inhibit dioxygen evolution, implicating an inner-sphere mechanism. Previously we showed that the reduced thiolate-ligated [Fe(II)(S(Me2)N(4)(tren))](+) (1) is capable of reducing O(2)(•−) via a proton-dependent inner-sphere mechanism involving a transient Fe(III)-OOH intermediate. A transient ferric-superoxo intermediate, [Fe(III)(S(Me2)N(4)(tren))(O(2))](+) (3), is detected by electronic absorption spectroscopy at −130 °C in the reaction between 1(ox)-THF and KO(2) and shown to evolve O(2) upon slight warming to −115 °C. The DFT calculated O–O (1.306 Å) and Fe–O (1.943 Å) bond lengths of 3 are typical of ferric-superoxo complexes, and the time-dependent DFT calculated electronic absorption spectrum of 3 reproduces the experimental spectrum. The electronic structure of 3 is shown to consist of two antiferromagnetically coupled (J(calc) = −180 cm(−1)) unpaired electrons, one in a superoxo π*(O–O) orbital and the other in an antibonding π*(Fe(d(yz))–S(p(y))) orbital. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|