期刊
JOURNAL OF CATALYSIS
卷 344, 期 -, 页码 768-777出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2016.08.013
关键词
Ferryl; Axial ligand; Additives; Co-catalyst; Chlorophenol; Chlorinated pollutants; DFT; Heme
资金
- European Union [8211]
- Greek national funds through the Operational Program Education and Lifelong Learning of the National Strategic Reference Framework (NSRF) - Research Funding Program: THALIS
- European Social Fund
- TALENTS FVG Programme from the European Social Fund
Electrostatic interactions occurring in the immediate environment of the metal center in native enzymes influence the charge distribution and electron donation ability, regulating activity. Herein, using an iron-porphyrin biomimetic complex, we have investigated the effect of the protonation state of the axial imidazole on the catalytic oxidation of pentachlorophenol. We show that the catalytic efficiency is drastically affected by the anionic state of the axial ligand. The chemical events occurring during the catalytic cycle were monitored by a detailed analytical study. EPR, UV-Vis and low temperature UV-Vis together with theoretical DFT and TD-DFT calculations provide evidence that deprotonation of the axial imidazole leads to increased electron donation ability to the central metal, enhancing the formation of ferryl species. lmidazole favored the formation of a pure porphyrin-radical model at the high-valent Fe-IV=OPor(+). state while imidazolate presented a significant axial ligand-radical character. The theoretical calculations suggest that the enhanced catalytic activity of the deprotonated conformation is attributed to the increased electron donation ability, favoring the formation of the ferryl species and suggesting that the push effect prevails over the pull effect. (C) 2016 Elsevier Inc. All rights reserved.
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