Characterization of the Oxygen Binding Motif in a Ruthenium Water Oxidation Catalyst by Vibrational Spectroscopy |
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Authors: | Erin M. Duffy Dr. Brett M. Marsh Jonathan M. Voss Prof. Etienne Garand |
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Affiliation: | Department of Chemistry, University of Wisconsin, Madison, WI, USA |
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Abstract: | For homogeneous mononuclear ruthenium water oxidation catalysts, the Ru–O2 complex plays a crucial role in the rate determining step of the catalytic cycle, but the exact nature of this complex is unclear. Herein, the infrared spectra of the [Ru(tpy)(bpy)(O2)]2+ complex (tpy=2,2′:6′,2′′‐terpyridine; bpy=2,2′‐bipyridine) are presented. The complex [Ru(tpy)(bpy)(O2)]2+, formed by gas‐phase reaction of [Ru(tpy)(bpy)]2+ with molecular O2, was isolated by using mass spectrometry and was directly probed by cryogenic ion IR predissociation spectroscopy. Well‐resolved spectral features enable a clear identification of the O?O stretch using 18O2 substitution. The band frequency and intensity indicate that the O2 moiety binds to the Ru center in a side‐on, bidentate manner. Comparisons with DFT calculations highlight the shortcomings of the B3LYP functional in properly depicting the Ru–O2 interaction. |
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Keywords: | homogeneous catalysis ion– molecule reactions IR spectroscopy laser spectroscopy reactive intermediates |
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