Water as a proton mediator for dioxygen-selective oxidation of alcohols by a planar dinuclear butterfly-like CuCu bonding complex: A combined experimental and computational study

- We studied butterfly-like Cu2(ophen)2 for dioxygen selective oxidation of alcohols.
- DFT calculations and ESI-MS experiments were used to study the reaction mechanism.
- Superoxide/peroxide and hydroperoxide in the cycle of oxidation were experienced.
- “Stretched-folded-stretched” configuration changes of Cu-complex were experienced.
- The role of H2O as proton mediator was revealed in the L2Cu2-O2 cyclical process.

The selective catalytic oxidation of alcohols is important both in laboratory and industrial production, and traditional oxidants cause environmentally lethal wastes. The development of dioxygen selective oxidation efficient has been pursued from atom-efficient, economic and environmental view of points. Using DFT calculation and ESI-MS experiments, we studied the activation of the CuCu bonded planar complex Cu2(ophen)2 to dioxygen and the application of the dioxygen-copper system for the selective oxidation of alcohols. For practical application and green chemistry, this catalytic system avoided the use of a large excess of base and expensive nitroxyl derivatives. In the cycle of oxidation, two oxidative dehydrogenation processes featuring superoxide/peroxide (I) and hydroperoxide (II) occurred along with a series of conformational changes of the butterfly-like Cu-complex from stretched to folded to stretched. Additionally, we characterized the role of the water molecule as a proton mediator in the dioxygen-copper system.

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