UNIGE document Scientific Article
previous document  unige:4845  next document
add to browser collection
Title

The Ru−Hbpp water oxidation catalyst

Authors
Bozoglian, Fernando
Romain, Sophie
Ertem, Mehmed Z.
Todorova, Tanya Kumanova
Sens, Christina
Mola, Joaquim
Rodriguez, Montserrat
Romero, Isabel
show hidden authors show all authors [1 - 13]
Published in Journal of the American Chemical Society. 2009, vol. 131, no. 42, p. 15176-15187
Abstract A thorough characterization of the Ru−Hbpp (in,in-{[RuII(trpy)(H2O)]2(μ-bpp)}3+ (trpy is 2,2':6',2''-terpyridine, bpp is bis(2-pyridyl)-3,5-pyrazolate)) water oxidation catalyst has been carried out employing structural (single crystal X-ray), spectroscopic (UV−vis and NMR), kinetic, and electrochemical (cyclic voltammetry) analyses. The latter reveals the existence of five different oxidation states generated by sequential oxidation of an initial II,II state to an ultimate, formal IV,IV oxidation state. Each of these oxidation states has been characterized by UV−vis spectroscopy, and their relative stabilities are reported. The electron transfer kinetics for individual one-electron oxidation steps have been measured by means of stopped flow techniques at temperatures ranging from 10 to 40 °C and associated second-order rate constants and activation parameters (ΔH and ΔS) have been determined. Room-temperature rate constants for substitution of aqua ligands by MeCN as a function of oxidation state have been determined using UV−vis spectroscopy. Complete kinetic analysis has been carried out for the addition of 4 equiv of oxidant (CeIV) to the initial Ru−Hbpp catalyst in its II,II oxidation state. Subsequent to reaching the formal oxidation state IV,IV, an intermediate species is formed prior to oxygen evolution. Intermediate formation and oxygen evolution are both much slower than the preceding ET processes, and both are first order with regard to the catalyst; rate constants and activation parameters are reported for these steps. Theoretical modeling at density functional and multireference second-order perturbation theory levels provides a microscopic mechanism for key steps in intermediate formation and oxygen evolution that are consistent with experimental kinetic data and also oxygen labeling experiments, monitored via mass spectrometry (MS), that unambiguously establish that oxygen−oxygen bond formation proceeds intramolecularly. Finally, the Ru−Hbpp complex has also been studied under catalytic conditions as a function of time by means of manometric measurements and MS, and potential deactivation pathways are discussed.
Identifiers
Full text
Article (Published version) (549 Kb) - document accessible for UNIGE members only Limited access to UNIGE
Other version: http://pubs.acs.org/doi/pdf/10.1021/ja9036127
Structures
Research group Groupe Gagliardi
Citation
(ISO format)
BOZOGLIAN, Fernando et al. The Ru−Hbpp water oxidation catalyst. In: Journal of the American Chemical Society, 2009, vol. 131, n° 42, p. 15176-15187. https://archive-ouverte.unige.ch/unige:4845

137 hits

3 downloads

Update

Deposited on : 2010-01-22

Export document
Format :
Citation style :