Activation of Dioxygen by a TAML Activator in Reverse Micelles: Characterization of an Fe(III)Fe(IV) Dimer and Associated Catalytic Chemistry.

Autor:	Tang LL; Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States., Gunderson WA; Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States., Weitz AC; Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States., Hendrich MP; Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States., Ryabov AD; Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States., Collins TJ; Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
Jazyk:	angličtina
Zdroj:	Journal of the American Chemical Society [J Am Chem Soc] 2015 Aug 05; Vol. 137 (30), pp. 9704-15. Date of Electronic Publication: 2015 Jul 23.
DOI:	10.1021/jacs.5b05229
Abstrakt:	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(III)Fe(IV) (major) and Fe(IV)Fe(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(III)Fe(IV) dimer has been characterized by UV-vis, EPR, and Mössbauer 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 "drier micelles") 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. Competing Interests: Notes The authors declare no competing financial interest.
Databáze:	MEDLINE
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