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Title: Incorporation of Hydrogen Bonding Functionalities into the Second Coordination Sphere of Iron-Based Water Oxidation Catalysts

Energy storage and conversion schemes based on environmentally benign chemical fuels will require the discovery of faster, cheaper, and more robust catalysts for the oxygen evolution reaction (OER). Although pendant bases have led to enhanced turnover frequencies with non-aqueous substrates, their effect on the catalytic behavior of molecular water oxidation catalysts has received little attention. Herein, the syntheses, structures, and catalytic activities of new iron complexes with pendant bases are reported. Of these, the complex [Fe(mepydz)4(CH3CN)2](OTf)2 (mepydz = N,N'-dimethyl-N,N'-bis(pyridazin-3-ylmethyl)ethane-1,2-diamine, OTf = trifluoromethanesulonate) (8(CH3CN)22+) is the most active catalyst. Initial turnover frequencies of 141 h-1 and 24 h-1 were measured using ceric ammonium nitrate at pH 0.7 and sodium periodate at pH 4.7, respectively. At pH 4.7, 8(CH3CN)22+ the initial turnover frequency is 70% faster than the structurally analogous complex without ancillary proton relays. These results demonstrate that the incorporation of pendant bases into molecular water oxidation catalysts is a synthetic principle that should be considered in the development of new OER catalysts. This work was supported by Laboratory Directed Research and Development program at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the US Department of Energy.
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Journal Article
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Journal Name: European Journal of Inorganic Chemistry, 2013(22-23):3846-3857
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
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Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY water oxidation; proton relays; cataysis; iron