Activation of Dioxygen by a TAML Activator in Reverse Micelles: Characterization of an FeIIIFeIV Dimer and Associated Catalytic Chemistry

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• 作者：Liang L. Tang ; William A. Gunderson ; Andrew C. Weitz ; Michael P. Hendrich ; Alexander D. Ryabov ; Terrence J. Collins
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：August 5, 2015
• 年：2015
• 卷：137
• 期：30
• 页码：9704-9715
• 全文大小：748K
• ISSN：1520-5126

文摘

Iron TAML activators of peroxides are functional catalase-peroxidase mimics. Switching from hydrogen peroxide (H₂O₂) to dioxygen (O₂) as the primary oxidant was achieved by using a system of reverse micelles of Aerosol OT (AOT) in n-octane. Hydrophilic TAML activators are localized in the aqueous microreactors of reverse micelles where water is present in much lower abundance than in bulk water. n-Octane serves as a proximate reservoir supplying O₂ to result in partial oxidation of Fe^III to Fe^IV-containing species, mostly the Fe^IIIFe^IV (major) and Fe^IVFe^IV (minor) dimers which coexist with the Fe^III TAML monomeric species. The speciation depends on the pH and the degree of hydration w₀, viz., the amount of water in the reverse micelles. The previously unknown Fe^IIIFe^IV dimer has been characterized by UV鈥搗is, EPR, and M枚ssbauer spectroscopies. Reactive electron donors such as NADH, pinacyanol chloride, and hydroquinone undergo the TAML-catalyzed oxidation by O₂. The oxidation of NADH, studied in most detail, is much faster at the lowest degree of hydration w₀ (in 鈥渄rier micelles鈥? and is accelerated by light through NADH photochemistry. Dyes that are more resistant to oxidation than pinacyanol chloride (Orange II, Safranine O) are not oxidized in the reverse micellar media. Despite the limitation of low reactivity, the new systems highlight an encouraging step in replacing TAML peroxidase-like chemistry with more attractive dioxygen-activation chemistry.