title: Characterization of the Oxygen Binding Motif in a Ruthenium Water Oxidation Catalyst by Vibrational Spectroscopy.
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 (18) O2 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.
authors.affiliation: Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI, 53706, USA.
authors.forename: Erin M
authors.identifier: http://orcid.org/0000-0003-0073-9529
authors.initials: EM
authors.lastname: Duffy
authors.affiliation: Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI, 53706, USA.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Marsh
authors.affiliation: Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI, 53706, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Voss
authors.affiliation: Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI, 53706, USA. egarand@chem.wisc.edu.
authors.forename: Etienne
authors.identifier: http://orcid.org/0000-0001-5062-5453
authors.initials: E
authors.lastname: Garand
keywords: IR spectroscopy; homogeneous catalysis; ion-molecule reactions; laser spectroscopy; reactive intermediates