Inhibitory Effect of Water on the Oxygen Reduction Catalyzed by Cobalt(II) Tetraphenylporphyrin

0427152 - ÚFCH JH 2015 RIV US eng J - Článek v odborném periodiku
Trojánek, Antonín - Langmaier, Jan - Kvapilová, Hana - Záliš, Stanislav - Samec, Zdeněk
Inhibitory Effect of Water on the Oxygen Reduction Catalyzed by Cobalt(II) Tetraphenylporphyrin.
Journal of Physical Chemistry A. Roč. 118, č. 11 (2014), s. 2018-2028. ISSN 1089-5639. E-ISSN 1520-5215
Grant CEP: GA ČR GAP208/11/0697
Institucionální podpora: RVO:61388955
Klíčová slova: electrochemistry * porphyrins * biomimetic catalysts
Kód oboru RIV: CF - Fyzikální chemie a teoretická chemie
Impakt faktor: 2.693, rok: 2014

Stopped- fl ow kinetic measurements, UV − vis spectroscopy, rotating disk voltammetry, and quantum chemical calculations are used to clarify the role of water in the homogeneous two-electron reduction of O 2 to H 2 O 2 in 1,2-dichloroethane (DCE) using ferrocene (Fc) as an electron donor, tetrakis(penta fl uorophenyl)boric acid (HTB) as a proton donor, and [5,10,15,20-tetraphenyl-21 H ,23 H - porphine]cobalt(II) (Co II TTP) as a catalyst. Kinetic analysis suggests that the reaction is controlled by the intramolecular proton coupled electron transfer to the O 2 molecule coordinated to the metal center producing the O 2 H • radical. This rate- determining step is common to both the O 2 reduction by Fc catalyzed by Co II TPP and the O 2 reduction by Co II TPP itself. Experimental data point to the competitive coordination of water to the metal center leading to a strong inhibition of the catalytic reaction. In agreement with this finding, quantum chemical calculations indicate that water is bound to the metal center much more strongly than triplet O2. A similar effect is demonstrated also for the O2 reduction catalyzed by the porphyrin free base (H2 TPP), though its rate is lower by 2 orders of magnitude.
Trvalý link: http://hdl.handle.net/11104/0232790