“0 孔”和“1 孔”状态的 Cu4S 簇：N2O 还原酶活性 CuZ* 位点的几何和电子结构变化,Journal of the American Chemical Society

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“0 孔”和“1 孔”状态的 Cu4S 簇：N2O 还原酶活性 CuZ* 位点的几何和电子结构变化
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2023-08-11 , DOI: 10.1021/jacs.3c04893
Yang Liu ₁ , Sayanti Chatterjee ₂ , George E Cutsail _{2,

3} , Sergey Peredkov ₂ , Sandeep K Gupta ₁ , Sebastian Dechert ₁ , Serena DeBeer ₂ , Franc Meyer _{1,

4}

Affiliation

一氧化二氮还原酶 (N ₂ OR) 是反硝化过程中的关键酶，其活性位点具有独特的 μ ₄ -硫桥四核 Cu 簇（所谓的 Cu _Z或 Cu _Z * 位点）。催化机制的细节仍然存在争议，迄今为止，由于构建独特的{Cu ₄ (μ ₄ -S)}核心结构的困难，Cu _Z */Cu _{Z位点的合成模型复合物极其罕见。}在此，我们报道了由大环 {py ₂ NHC ₄ } 配体（py = 吡啶）支持的 [Cu ₄ (μ ₄ -S)] ⁿ⁺ ( n = 2, 2 ; n = 3, 3 ) 簇的合成和表征，NHC = N-杂环卡宾），处于 0 孔 ( 2 ) 和 1-孔 ( 3 ) 状态，从而模拟酶促 N ₂ O 还原过程中Cu _Z * 位点的两种活性状态。通过采用多种方法阐明了这些{Cu ₄ (μ ₄ -S)}团簇的结构和电子性质，包括X射线衍射(XRD)、核磁共振(NMR)、UV/vis、电子顺磁共振(EPR) 、Cu/S K 边 X 射线发射光谱 (XES) 和 Cu K 边 X 射线吸收光谱 (XAS) 与时间相关密度泛函理论 (TD-DFT) 计算相结合。_{{Cu 4} (μ ₄ -S)} 核从2 (τ ₄ (S) = 0.46，跷跷板) 氧化到3 (τ ₄ (S) = 0.03，方形平面) 时会发生显着的几何变化，其中迄今为止，生物 Cu _Z (*) 位点尚未观察到，这对于已知的模型复合物来说是前所未有的。1 孔物种3的单电子主要通过中心 S 原子在两个相对的 Cu 离子上离域，由 π/π 超交换途径介导。Cu K-edge XAS 和 Cu/S K-edge XES 证实了基于 Cu/S 的混合氧化事件，其中最低未占分子轨道 (LUMO) 具有显着的 S 特征。此外，初步反应性研究证明中心μ ₄ -S在完全还原的0-空穴状态下具有亲核特性。

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Cu4S Cluster in “0-Hole” and “1-Hole” States: Geometric and Electronic Structure Variations for the Active CuZ* Site of N2O Reductase

The active site of nitrous oxide reductase (N₂OR), a key enzyme in denitrification, features a unique μ₄-sulfido-bridged tetranuclear Cu cluster (the so-called Cu_Z or Cu_Z* site). Details of the catalytic mechanism have remained under debate and, to date, synthetic model complexes of the Cu_Z*/Cu_Z sites are extremely rare due to the difficulty in building the unique {Cu₄(μ₄-S)} core structure. Herein, we report the synthesis and characterization of [Cu₄(μ₄-S)]ⁿ⁺ (n = 2, 2; n = 3, 3) clusters, supported by a macrocyclic {py₂NHC₄} ligand (py = pyridine, NHC = N-heterocyclic carbene), in both their 0-hole (2) and 1-hole (3) states, thus mimicking the two active states of the Cu_Z* site during enzymatic N₂O reduction. Structural and electronic properties of these {Cu₄(μ₄-S)} clusters are elucidated by employing multiple methods, including X-ray diffraction (XRD), nuclear magnetic resonance (NMR), UV/vis, electron paramagnetic resonance (EPR), Cu/S K-edge X-ray emission spectroscopy (XES), and Cu K-edge X-ray absorption spectroscopy (XAS) in combination with time-dependent density functional theory (TD-DFT) calculations. A significant geometry change of the {Cu₄(μ₄-S)} core occurs upon oxidation from 2 (τ₄(S) = 0.46, seesaw) to 3 (τ₄(S) = 0.03, square planar), which has not been observed so far for the biological Cu_Z(*) site and is unprecedented for known model complexes. The single electron of the 1-hole species 3 is predominantly delocalized over two opposite Cu ions via the central S atom, mediated by a π/π superexchange pathway. Cu K-edge XAS and Cu/S K-edge XES corroborate a mixed Cu/S-based oxidation event in which the lowest unoccupied molecular orbital (LUMO) has a significant S-character. Furthermore, preliminary reactivity studies evidence a nucleophilic character of the central μ₄-S in the fully reduced 0-hole state.

更新日期：2023-08-11

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