Mass Spectrometric and Vibrational Characterization of Reaction Intermediates in [Ru(bpy)(tpy)(H2 O)]2+ Catalyzed Water Oxidation.

Mass spectrometry coupled with an in-line electrochemical electrospray ionization source is used to capture some of the reaction intermediates formed in the [Ru(bpy)(tpy)(H2 O)]2+ (bpy=2,2'-bipyridine, tpy=2,2':6',2"-terpyridine) catalyzed water oxidation reaction. By controlling the applied electrochemical potential, we identified the parent complex, as well as the first two oxidation complexes, identified as [Ru(bpy)(tpy)(OH)]2+ and [Ru(bpy)(tpy)(O)]2+ . The structures of the parent and first oxidation complexes are probed directly in the mass spectrometer by using infrared predissociation spectroscopy of D2 -tagged ions. Comparisons between experimental vibrational spectra and density functional theory calculations confirmed the identity and structure of these two complexes. Moreover, the frequency of the O-H stretching mode in [Ru(bpy)(tpy)(OH)]2+ shows that this complex features a Ru-OH interaction that is more covalent than ionic.