期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：2
页码：623-628
DOI：10.1073/pnas.1314885111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In a fundamental process throughout nature, reduced iron unleashes the oxidative power of hydrogen peroxide into reactive intermediates. However, notwithstanding much work, the mechanism by which Fe2+ catalyzes H2O2 oxidations and the identity of the participating intermediates remain controversial. Here we report the prompt formation of O=FeIVCl3- and chloride-bridged di-iron O=FeIV{middle dot}Cl{middle dot}FeIICl4- and O=FeIV{middle dot}Cl{middle dot}FeIIICl5- ferryl species, in addition to FeIIICl4-, on the surface of aqueous FeCl2 microjets exposed to gaseous H2O2 or O3 beams for <50 s. The unambiguous identification of such species in situ via online electrospray mass spectrometry let us investigate their individual dependences on Fe2+, H2O2, O3, and H+ concentrations, and their responses to tert-butanol (an {middle dot}OH scavenger) and DMSO (an O-atom acceptor) cosolutes. We found that (i) mass spectra are not affected by excess tert-butanol, i.e., the detected species are primary products whose formation does not involve {middle dot}OH radicals, and (ii) the di-iron ferryls, but not O=FeIVCl3-, can be fully quenched by DMSO under present conditions. We infer that interfacial Fe(H2O)n2+ ions react with H2O2 and O3 >103 times faster than Fe(H2O)62+ in bulk water via a process that favors inner-sphere two-electron O-atom over outer-sphere one-electron transfers. The higher reactivity of di-iron ferryls vs. O=FeIVCl3- as O-atom donors implicates the electronic coupling of mixed-valence iron centers in the weakening of the FeIV-O bond in poly-iron ferryl species.
