A cobalt porphyrin complex with a pendant imidazole base ([(L1)CoII]) is an efficient catalyst for the homogeneous catalytic two-electron reduction of dioxygen by 1,1′-dimethylferrocene (Me2Fc) in the presence of triflic acid (HOTf), as compared with a cobalt porphyrin complex without a pendant imidazole base ([(L2)CoII]). The pendant imidazole ligand plays a crucial role not only to provide an imidazolinium proton for proton-coupled electron transfer (PCET) from [(L1)CoII] to O2 in the presence of HOTf but also to facilitate electron transfer (ET) from [(L1)CoII] to O2 in the absence of HOTf. The kinetics analysis and the detection of intermediates in the stoichiometric and catalytic reduction of O2 have provided clues to clarify the crucial roles of the pendant imidazole ligand of [(L1)CoII] for the first time.
Bibliographical noteFunding Information:
This work was supported by the NRF of Korea (NRF‐2021R1A3B1076539 to W.N and NRF‐2020R1I1A1A01074630 to Y.‐M.L.), the National Natural Science Foundation of China (21773146 and 22171176), Fok Ying‐Tong Education Foundation for Outstanding Young Teachers in University, Fundamental Research Funds for the Central Universities, Research Funds of Shaanxi Normal University to R.C., and the National Natural Science Foundation of China (22102092) and the China Postdoctoral Science Foundation (2019M663614) to X.L.
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- Acid-Promoted Electron Transfer
- Cobalt Porphyrin Complex
- Pendant Imidazole Base
- Reaction Mechanisms
- Reduction of Dioxygen