Mechanistic Analysis of Water Oxidation Catalyst cis-Rubpy2H2O22 : Effect of DimerizationReport as inadecuate


Mechanistic Analysis of Water Oxidation Catalyst cis-Rubpy2H2O22 : Effect of Dimerization


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Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USA



These authors contributed equally to this work.





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Academic Editors: Albert Demonceau, Ileana Dragutan and Valerian Dragutan

Abstract While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex Rubpy2H2O22+ bpy = 2,2′-bipyridine—which can exist as either a cis isomer or a trans isomer—is investigated. While a difference in the catalytic activity of these two isomers is well established, with cis-Rubpy2H2O22+ being much more active, no mechanistic explanation of this fact has been presented. The oxygen evolving capability of both isomers at multiple concentrations has been investigated, with cis-Rubpy2H2O22+ showing a second-order dependence of O2 evolution activity with increased catalyst concentration. Measurement of the electron paramagnetic resonance EPR spectrum of cis-Rubpy2H2O22+, shortly after oxidation with CeIV, showed the presence of a signal matching that of cis,cis-RuIIIbpy2H2OORuIVbpy2OH4+, also known as -blue dimer-. The formation of dimers is a concentration-dependent process, which could serve to explain the greater than first order increase in catalytic activity. The trans isomer showed a first-order dependence of O2 evolution on catalyst concentration. Behavior of Rubpy2H2O22+ isomers is compared with other Ru-based catalysts, in particular RutpybpyH2O2+ tpy = 2,2′;6,2′′-terpyridine. View Full-Text

Keywords: Ru complexes; catalysis of water oxidation; density functional theory; X-band EPR spectroscopy; oxygen evolution; H-bond; dimer formation Ru complexes; catalysis of water oxidation; density functional theory; X-band EPR spectroscopy; oxygen evolution; H-bond; dimer formation





Author: Darren Erdman †, Yuliana Pineda-Galvan † and Yulia Pushkar *

Source: http://mdpi.com/



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