Liu Yan Fang, Du Likai
The Key Laboratory of Biobased Materials, The Qingdao Key Lab of Solar Energy Utilization and Energy Storage Technology, Qingdao Institute of Bioenergy and Bioprocess Technology , Chinese Academy of Sciences , Qingdao , Shandong 266101 , People's Republic of China.
Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics , Huazhong Agricultural University , Wuhan , 430070 , People's Republic of China.
Inorg Chem. 2018 Mar 19;57(6):3261-3271. doi: 10.1021/acs.inorgchem.8b00054. Epub 2018 Mar 5.
The reactivity patterns of a series of trivalent copper complexes have been studied to gain a better understanding of the chemical reactions occurring at the active site of particulate methane monooxygenase (pMMO). In this study, hybrid density functional theory is used to study the oxidation of methane to methanol mediated by the [CuCu(μ-O)Cu(7- N-Etppz)] complex. Reaction mechanisms in different spin states were explored. Based on the calculated free-energy profile, a mechanism is suggested for the reaction of the oxidation of methane to methanol. The first step (1 → 2) is a hydrogen transfer to the bridged oxygen in the CuO core from the methane to form a methyl radical. The second step (2 → 3) is the radical recombination, in which the bridged hydroxyl rotates upward and exposes the oxygen moiety toward the methyl radical to form methanol. The radical recombination step is rate-limiting, with a calculated free-energy barrier of 19.6 kcal mol, which is in good agreement with the experimental value of 18.4 kcal mol. The mixed valent bis(μ-oxo)CuCu species in the CuO core is directly responsible for the C-H activation of methane.
研究了一系列三价铜配合物的反应模式，以便更好地理解颗粒状甲烷单加氧酶（pMMO）活性位点发生的化学反应。在本研究中，采用杂化密度泛函理论研究了[CuCu(μ-O)Cu(7-N-Etppz)]配合物介导的甲烷氧化为甲醇的反应。探索了不同自旋态下的反应机理。基于计算得到的自由能剖面图，提出了甲烷氧化为甲醇反应的一种机理。第一步（1→2）是氢从甲烷转移到CuO核中的桥连氧上，形成甲基自由基。第二步（2→3）是自由基重组，其中桥连羟基向上旋转，使氧部分朝向甲基自由基，形成甲醇。自由基重组步骤是限速步骤，计算得到的自由能垒为19.6 kcal mol，与18.4 kcal mol的实验值吻合良好。CuO核中的混合价双（μ-氧代）CuCu物种直接负责甲烷的C-H活化。
