Emulating the capabilities of the soluble methane monooxygenase (sMMO) enzymes, which effortlessly activate oxygen at diiron(II) centers to form a reactive diiron(IV) intermediate Q, which then performs the challenging oxidation of methane to methanol, poses a significant challenge. Very recently, one of us reported the mononuclear complex [(cyclam)Fe^II(CH₃CN)₂]²⁺ (1), which performed a rare bimolecular activation of the molecule of O₂ to generate two molecules of Fe^IV═O without the requirement of external proton or electron sources, similar to sMMO. In the present study, we employed the density functional theory (DFT) calculations to investigate this unique mechanism of O₂ activation. We show that secondary hydrogen-bonding interactions between ligand N–H groups and O₂ play a vital role in reducing the energy barrier associated with the initial O₂ binding at 1 and O–O bond cleavage to form the Fe^IV═O complex. Further, the unique reactivity of Fe^IV═O species toward simultaneous C–H and O–H bond activation process has been demonstrated. Our study unveils that the nature of the magnetic coupling between the diiron centers is also crucial. Given that the influence of magnetic coupling and noncovalent interactions in catalysis remains largely unexplored, this unexplored realm presents numerous avenues for experimental chemists to develop novel structural and functional analogues of sMMO.

中文翻译：

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通过氧活化形成 FeIV=O 物种前所未有的形成和反应性的起源：非共价相互作用和磁耦合的作用


模拟可溶性甲烷单加氧酶 (sMMO) 的功能是一项重大挑战，该酶可以轻松地激活二铁 (II) 中心的氧，形成反应性二铁 (IV) 中间体 Q，然后将甲烷氧化为甲醇，从而完成具有挑战性的氧化反应。最近，我们中的一个人报道了单核配合物 [(cyclam)Fe ^II (CH ₃ CN) ₂ ] ²⁺ (1 ），它对 O ₂ 分子进行了罕见的双分子活化，生成两个 Fe ^IV =O 分子，无需外部质子或电子源，类似于 sMMO。在本研究中，我们采用密度泛函理论（DFT）计算来研究O ₂ 激活的这种独特机制。我们表明，配体 N–H 基团和 O ₂ 之间的二次氢键相互作用在降低与初始 O ₂ 在 1 和 O– 结合相关的能垒方面发挥着至关重要的作用。 O键断裂形成Fe ^IV =O络合物。此外，Fe ^IV =O 物种对同时 C-H 和 O-H 键激活过程的独特反应性已得到证明。我们的研究表明，二铁中心之间的磁耦合性质也至关重要。鉴于磁耦合和非共价相互作用在催化中的影响在很大程度上仍未被探索，这一未探索的领域为实验化学家提供了多种途径来开发 sMMO 的新型结构和功能类似物。