Enzymes exert control over the reactivity of metal centers with precise tuning of the secondary coordination sphere of active sites. One particularly elegant illustration of this principle is in the controlled delivery of proton and electron equivalents in order to activate abundant but kinetically inert oxidants such as O₂ for oxidative chemistry. Chemists have drawn inspiration from biology in designing molecular systems where the secondary coordination sphere can shuttle protons or electrons to substrates. However, a biomimetic activation of O₂ requires the transfer of both protons and electrons, and molecular systems where ancillary ligands are designed to provide both of these equivalents are comparatively rare. Here, we report the use of a dihydrazonopyrrole (DHP) ligand complexed to Fe to perform exactly such a biomimetic activation of O₂. In the presence of O₂, this complex directly generates a high spin Fe(III)-hydroperoxo intermediate which features a DHP^• ligand radical via ligand-based transfer of an H atom. This system displays oxidative reactivity and ultimately releases hydrogen peroxide, providing insight on how secondary coordination sphere interactions influence the evolution of oxidizing intermediates in Fe-mediated aerobic oxidations.

中文翻译：

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通过预先组织的二级协调球直接有氧生成过氧化铁中间体

酶通过精确调节活性位点的二级配位范围来控制金属中心的反应性。这一原理的一个特别优雅的例子是质子和电子等价物的受控传递，以激活大量但动力学惰性的氧化剂，例如用于氧化化学的 O _{2 。}化学家在设计分子系统时从生物学中汲取灵感，其中二级配位球可以将质子或电子穿梭到底物上。然而，O ₂的仿生激活需要质子和电子和设计辅助配体以提供这两种等效物的分子系统相对较少。在这里，我们报告了使用与 Fe 络合的二腙并吡咯 (DHP) 配体来进行 O ₂的这种仿生活化。在O ₂存在的情况下，该配合物直接生成高自旋Fe(III)-氢过氧中间体，该中间体通过H 原子的基于配体的转移而具有DHP ^{•配体自由基。}该系统显示出氧化反应性并最终释放过氧化氢，从而深入了解二次配位球相互作用如何影响 Fe 介导的有氧氧化中氧化中间体的演变。