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<p>Dioxygen activation at iron centers is central to many biological and synthetic oxidation processes. In proteins, the reactivity and stability of iron–dioxygen intermediates are often controlled by secondary-sphere interactions such as hydrogen bonding. For example, hemoglobin stabilizes a Fe−O<sub>2</sub> adduct through distal hydrogen bonding, while hemerythrin employs hydrogen bonding to stabilize reduced oxygen species within a diiron active site, enabling reversible O<sub>2</sub> binding. Here we show that a mononuclear nonheme iron complex, [Fe<sup>II</sup>(DIG<sub>3</sub>tren)]<sup>2+</sup> (DIG<sub>3</sub>tren = tris(N’,N”-diisopropylguanidinyl-2-ethyl)amine), reversibly reduces O<sub>2</sub> by two electrons to generate an iron(IV)-peroxido species. Strong hydrogen bonds from N − H groups of the ligand stabilize the O<sub>2</sub><sup>2−</sup> ligand, while the electron-rich guanidine donors promote the unusual Fe<sup>II</sup>-mediated two-electron reduction of O<sub>2</sub>. As a result, the complex exhibits higher affinity for O<sub>2</sub> than for CO due to preferential hydrogen-bond stabilization of the peroxido intermediate. These results demonstrate how secondary-sphere design can control both O<sub>2</sub> activation and ligand selectivity at iron centers.</p>

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A mononuclear nonheme iron complex with higher affinity for O2 than CO via hydrogen bonding

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月5日

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  • Matthias Jux,
  • Stefan Mebs,
  • Michael Haumann,
  • Sagie Katz,
  • Ricardo Garcia-Serres,
  • Peter Hildebrandt,
  • Yong Wang,
  • Wonwoo Nam,
  • Kallol Ray

摘要

Dioxygen activation at iron centers is central to many biological and synthetic oxidation processes. In proteins, the reactivity and stability of iron–dioxygen intermediates are often controlled by secondary-sphere interactions such as hydrogen bonding. For example, hemoglobin stabilizes a Fe−O2 adduct through distal hydrogen bonding, while hemerythrin employs hydrogen bonding to stabilize reduced oxygen species within a diiron active site, enabling reversible O2 binding. Here we show that a mononuclear nonheme iron complex, [FeII(DIG3tren)]2+ (DIG3tren = tris(N’,N”-diisopropylguanidinyl-2-ethyl)amine), reversibly reduces O2 by two electrons to generate an iron(IV)-peroxido species. Strong hydrogen bonds from N − H groups of the ligand stabilize the O22− ligand, while the electron-rich guanidine donors promote the unusual FeII-mediated two-electron reduction of O2. As a result, the complex exhibits higher affinity for O2 than for CO due to preferential hydrogen-bond stabilization of the peroxido intermediate. These results demonstrate how secondary-sphere design can control both O2 activation and ligand selectivity at iron centers.