Mechanism of Nitrogen Reduction to Ammonia in a Diiron Model of Nitrogenase.
Mechanism of Nitrogen Reduction to Ammonia in a Diiron Model of Nitrogenase.
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DOI：
10.1021/acs.inorgchem.3c02089
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发表时间：
2023-09-11
影响因子：
4.6
通讯作者：
de Visser SP
中科院分区：
文献类型：
--
作者：
Barchenko M;O'Malley PJ;de Visser SP
固氮酶是生物学中一种非常有趣的酶，它通过逐步还原和质子化将空气中的二氮还原为氨。尽管实验和计算小组对固氮酶的催化循环进行了详细的研究，但仍有许多未知因素，特别是与质子和电子的添加及其顺序有关的因素。最近的一项仿生研究，其特征在于潜在的二氮桥连二铁簇作为固氮酶的合成模型。使用强酸和还原剂，二氮被转化为氨分子，但其机制的细节仍然未知。特别是，从实验研究中还不清楚质子和电子转移步骤是顺序的还是交替的。此外，这项工作未能确定二铁核心的功能是什么，以及它是否在反应过程中分裂成单核铁碎片。为了研究仿生二氮桥连双铁配合物[（P2P′PhFeH）2（μ-N2）]与三苯基膦配体的结构和反应性，采用密度泛函理论（DFT）研究了该配合物的结构和反应性.我们的计算方法进行了验证，对实验晶体结构坐标，穆斯堡尔参数和振动频率，并显示出良好的协议。随后，我们研究了交替和连续添加的电子和质子的系统。计算确定了一些可能的反应通道，即，相同的网站质子化，交替质子化，和复杂的解离成单核铁中心。计算表明，整个机制不是一个纯粹的顺序设置的电子和质子转移，而是交替和连续步骤的混合物。特别地，第一反应步骤将以双质子转移开始，随后是电子转移，而此后，存在另一个质子转移和第二个电子转移以得到络合物，由此氨可以以低能量势垒分裂。第二个通道开始于两个氮原子的交替质子化，之后是初始的双质子转移，电子和质子依次加入以形成肼结合的复合物。后者在进一步质子化后自发地分解氨。用价键图和轨道图分析了各种反应通道。我们预期固氮酶的运作与混合交替和连续的质子化和电子转移步骤。通过密度泛函理论计算，研究了μ-二氮桥联二铁配合物中二氮通过交替和连续途径还原为两个氨分子的反应机理和可能性.计算表明，通过混合交替和连续机制的多种可能途径是可行的。
Nitrogenase is a fascinating enzyme in biology that reduces dinitrogen from air to ammonia through stepwise reduction and protonation. Despite it being studied in detail by experimental and computational groups, there are still many unknown factors in the catalytic cycle of nitrogenase, especially related to the addition of protons and electrons and their order. A recent biomimetic study characterized a potential dinitrogen-bridged diiron cluster as a synthetic model of nitrogenase. Using strong acid and reductants, the dinitrogen was converted into ammonia molecules, but details of the mechanism remains unknown. In particular, it was unclear from the experimental studies whether the proton and electron transfer steps are sequential or alternating. Moreover, the work failed to establish what the function of the diiron core is and whether it split into mononuclear iron fragments during the reaction. To understand the structure and reactivity of the biomimetic dinitrogen-bridged diiron complex [(P2P′PhFeH)2(μ-N2)] with triphenylphosphine ligands, we performed a density functional theory study. Our computational methods were validated against experimental crystal structure coordinates, Mössbauer parameters, and vibrational frequencies and show excellent agreement. Subsequently, we investigated the alternating and consecutive addition of electrons and protons to the system. The calculations identify a number of possible reaction channels, namely, same-site protonation, alternating protonation, and complex dissociation into mononuclear iron centers. The calculations show that the overall mechanism is not a pure sequential set of electron and proton transfers but a mixture of alternating and consecutive steps. In particular, the first reaction steps will start with double proton transfer followed by an electron transfer, while thereafter, there is another proton transfer and a second electron transfer to give a complex whereby ammonia can split off with a low energetic barrier. The second channel starts with alternating protonation of the two nitrogen atoms, whereafter the initial double proton transfer, electrons and protons are added sequentially to form a hydrazine-bound complex. The latter split off ammonia spontaneously after further protonation. The various reaction channels are analyzed with valence bond and orbital diagrams. We anticipate the nitrogenase enzyme to operate with mixed alternating and consecutive protonation and electron transfer steps. Density functional theory calculations on a μ-dinitrogen bridged diiron complex investigate the reaction mechanisms and possibilities of dinitrogen reduction to two ammonia molecules through alternating and consecutive pathways. The calculations show that multiple possible pathways through mixed alternating and consecutive mechanisms are feasible.
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影响因子：
4.3
作者：
Ali, Hafiz Saqib;de Visser, Sam P.
通讯作者：
de Visser, Sam P.
DOI：
10.1002/anie.201703244
发表时间：
2017-06-06
期刊：
Angewandte Chemie (International ed. in English)
影响因子：
--
作者：
Buscagan TM;Oyala PH;Peters JC
通讯作者：
Peters JC
影响因子：
62.1
作者：
Baglia RA;Zaragoza JPT;Goldberg DP
通讯作者：
Goldberg DP
影响因子：
15
作者：
Creutz, Sidney E.;Peters, Jonas C.
通讯作者：
Peters, Jonas C.
合成单位Fe氮酶：高离职率，冻结（57）feMössbauer数据和氢化物静止状态。
影响因子：
15
作者：
Del Castillo TJ;Thompson NB;Peters JC
通讯作者：
Peters JC