cis,cis-[(bpy)RuO]O Catalyzes Water Oxidation Formally via in Situ Generation of Radicaloid Ru—O•.
The mechanism of the catalytic oxidation of water by cis,cis-[(bpy)2Ru(OH)] to give molecular dioxygen was investigated using Density Functional Theory (DFT). A series of four oxidation and four deprotonation events generate the catalytically competent species cis,cis-[(bpy)RuO]O, which breaks the H...
| Publicado en: | Journal of the American Chemical Society Vol. 128; no. 23; pp. 7476 - 7486 |
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| Autores principales: | , |
| Formato: | Artículo |
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American Chemical Society
6/14/2006
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=21306376&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 21306376 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 6/14/2006 vid: 128 iid: 23 pid: 997 pub: American Chemical Society artinfo: ui: 21306376 10.1021/ja053710j ppf: 7476 ppct: 10 formats: tig: atl: cis,cis-[(bpy)RuO]O Catalyzes Water Oxidation Formally via in Situ Generation of Radicaloid Ru—O•. aug: au: Xiaofan Yang Mu-Hyun Baik affil: Contribution from the Department of Chemistry and School of Informatics, Indiana University, Bloomington, Indiana 47405 su: Oxidation Density functionals Chemical bonds Oxidation-reduction reaction Protons Charge transfer sug: subj: Oxidation Density functionals Chemical bonds Oxidation-reduction reaction Protons Charge transfer ab: The mechanism of the catalytic oxidation of water by cis,cis-[(bpy)2Ru(OH)] to give molecular dioxygen was investigated using Density Functional Theory (DFT). A series of four oxidation and four deprotonation events generate the catalytically competent species cis,cis-[(bpy)RuO]O, which breaks the H-OH bond homolytically at the rate determining transition state to give a hydroperoxo intermediate. Our calculations predict a rate determining activation barrier of 25.9 kcal/mol in solution phase, which is in reasonable agreement with the previously reported experimental estimate of 18.7-23.3 kcal/mol. A number of plausible coupling schemes of the two metal sites including strong coupling, weak ferromagnetic and weak antiferromagnetic coupling have been considered. In addition, both high-spin and low-spin states at each of the Ru(V)-a centers were explored and we found that the high-spin states play an important mechanistic role. Our calculations suggest that cis,cis-[(bpy)2RuO]2O performs formally an intramolecular ligand-to-metal charge transfer when reacting with water to formally give a cis,cis-[(bpy)RuO.]2O complex. We propose that the key characteristic of the diruthenium catalyst that allows it to accomplish the most difficult first two oxidations of the overall four-electron redox reaction is directly associated with this in situ generation of two radicaloid oxo moieties that promote the water splitting reaction. A proton coupled metal-to-metal charge transfer follows to yield a Ru(V)/Ru(III) peroxo/aqua mixed valence complex, which performs the third redox reaction to give the superoxo/aqua complex. Finally, intersystem crossing to a ferromagnetically coupled Ru(IV)/Ru(lll) superoxo/aqua species is predicted, which will then promote the last redox event to release triplet dioxygen as the final product. A number of key features of the computed mechanism are explored in detail to derive a conceptual understanding of the catalytic mechanism. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2006 holdings: @attributes: islocal: N |
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