A Theoretical Study on the Enhancement of Functionally Relevant Electron Transfers in Biomimetic Models of [FeFe]-Hydrogenases
A Theoretical Study on the Enhancement of Functionally Relevant Electron Transfers in Biomimetic Models of [FeFe]-Hydrogenases
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DOI：
10.1021/ic200297d
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发表时间：
2011-08-01
影响因子：
4.6
通讯作者：
De Gioia, Luca
中科院分区：
文献类型：
--
作者：
Greco, Claudio;De Gioia, Luca
旨在模拟 [FeFe]-氢化酶活性位点化学的最新进展（H 簇，由催化 Fe2S2 亚簇和 Fe4S4 部分组成）已导致合成含有非无害有机膦配体 [2,3-双（二苯基膦）马来酸酐，bma] 的双核配位化合物，该配体能够进行单电子还原，类似于四核 Fe4S4 H 星团的子簇部分。然而，这种合成模型的特点是非无辜配体和簇的其余部分之间的电子通讯可以忽略不计，与酶活性位点不同。在这里，我们报告了一项理论研究，该研究表明为什么在催化 Fe2S2 子位点质子化时在酶中观察到的电子转移不能在含有 bma 的簇中发生。此外，我们表明，bma 配体的靶向修饰足以恢复模型内的电子通讯，由于铁中心的质子化，电子密度可以更容易地从非无辜配体中撤出。使用衍生自二茂钴的配体也获得了类似的结果。我们的研究结果的相关性是从质子还原产生分子氢的仿生再现的角度讨论的。
Recent advances aimed at modeling the chemistry of the active site of [FeFe]-hydrogenases (the H-duster, composed by a catalytic Fe2S2 subcluster and an Fe4S4 portion) have led to the synthesis of binuclear coordination compounds containing a noninnocent organophosphine ligand [2,3-bis(diphenylphosphino)maleic anhydride, bma] that is able to undergo monoelectron reduction, analogously to the tetranuclear Fe4S4 subduster portion of the H-cluster. However, such a synthetic model was shown to feature negligible electronic communication between the noninnocent ligand and the remaining portion of the cluster, at variance with the enzyme active site. Here, we report a theoretical investigation that shows why the electron transfer observed in the enzyme upon protonation of the catalytic Fe2S2 subsite cannot take place in the bma-containing cluster. In addition, we show that targeted modifications of the bma ligand are sufficient to restore the electronic communication within the model, such that electron density can be more easily withdrawn from the noninnocent ligand, as a result of protonation of the iron centers. Similar results were also obtained with a ligand derived from cobaltocene. The relevance of our findings is discussed from the perspective of biomimetic reproduction of proton reduction to yield molecular hydrogen.