期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 135, 期 8, 页码 3286-3299出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja400183g
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资金
- National Institutes of Health [GM 40392]
- NRF/MEST of Korea through CRI
- NRF/MEST of Korea through GRL [2010-00353]
- NRF/MEST of Korea through WCU [R31-2008-000-10010-0]
- National Research Foundation of Korea [2010-00353, 2012R1A3A2048842, R31-2012-000-10010-0] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
The geometric and electronic structures and reactivity of an S = 5/2 (HS) mononuclear nonheme (TMC)Fe-III-OOH complex are studied by spectroscopies, calculations, and kinetics and compared with the results of previous studies of S = 1/2 (LS) Fe-III-OOH complexes to understand parallels and differences in mechanisms of O-O bond homolysis and electrophilic H-atom abstraction reactions. The homolysis reaction of the HS [(TMC)Fe-III-OOH](2+) complex is found to involve axial ligand coordination and a crossing to the LS surface for O-O bond homolysis. Both HS and LS Fe-III-OOH complexes are found to perform direct H-atom abstraction reactions but with very different reaction coordinates. For the LS Fe-III-OOH, the transition state is late in O-O and early in C-H coordinates. However, for the HS Fe-III-OOH, the transition state is early in O-O and further along in the C-H coordinate. In addition, there is a significant amount of electron transfer from the substrate to the HS Fe-III-OOH at transition state, but that does not occur in the LS transition state. Thus, in contrast to the behavior of LS Fe-III-OOH, the H-atom abstraction reactivity of HS Fe-III-OOH is found to be highly dependent on both the ionization potential and the C-H bond strength of the substrate. LS Fe-III-OOH is found to be more effective in H-atom abstraction for strong C-H bonds, while the higher reduction potential of HS Fe-III-OOH allows it to be active in electrophilic reactions without the requirement of O-O bond cleavage. This is relevant to the Rieske dioxygenases, which are proposed to use a HS Fe-III-OOH to catalyze cis-dihydroxylation of a wide range of aromatic compounds.
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