Quantum Chemical Studies of Methane Oxidation to Methanol on a Biomimetic Tricopper Complex: Mechanistic Insights. Issue 18 (14th May 2018)

• Record Type: Journal Article
• Authors: Yeh, Chen‐Hao; Yu, Steve S.‐F.; Chan, Sunney I.; Jiang, Jyh‐Chiang
• Is Part Of: ChemistrySelect. Volume 3:Issue 18(2018)
• Page Start: 5113
• Page End: 5122
• Publication Date: 2018-05-14
• Subjects: C−H⋅⋅⋅O hydrogen bond -- Density functional theory -- Methane oxidation -- pMMO -- tri-copper cluster; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201800550
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Particulate methane monooxygenase (pMMO) is known to be the most efficient oxidizer for the conversion of methane (CH4 ) into methanol (CH3 OH) at room temperature. Recently, the tricopper cluster complex [Cu3 (7‐ N ‐Etppz)] 1+ has been shown to mediate facile CH4 oxidation upon activation by dioxygen (O2 ) just like the pMMO enzyme. In this work, we investigate by unrestricted density functional theory (DFT) calculations the oxidation of CH4 on the biomimetic tricopper complex. We find that CH4 can interact with the activated tricopper complex to form a C−H⋅⋅⋅O hydrogen bond between one of the C−H bonds of CH4 and the O2 molecule activating the tricopper cluster complex. We consider both the direct "oxene insertion" mechanism as well as the "hydrogen‐atom abstraction geminal radical rebound" mechanism for the process. Our calculations indicate low kinetic barriers for both reaction pathways, accounting for why the tricopper cluster of the biomimetic complex [Cu3 (7‐ N ‐Etppz)] 1+ is a good functional model of the active site in pMMO. Abstract : Herein, we investigate the mechanism of CH4 oxidation on a biomimetic tricopper complex, [Cu3 (7‐ N ‐Etppz)] 1+, by DFT calculation. We consider both the direct "oxene insertion" pathway as well as the "hydrogen‐atom abstraction geminal radical rebound" pathway. Our calculations indicate low kinetic barriers for both reaction pathways, accounting for why the tricopper cluster of the biomimetic complex [Cu3 (7‐ N ‐Etppz)] 1+ is a good functional model of the active site in pMMO.