Water exchange on manganese(III) porphyrins. Mechanistic insights relevant for oxygen evolving complex and superoxide dismutation catalysis

Journal article
(Original article)


Publication Details

Author(s): Lieb D, Zahl A, Shubina T, Ivanovic-Burmazovic I
Journal: Journal of the American Chemical Society
Publisher: American Chemical Society
Publication year: 2010
Volume: 132
Journal issue: 21
Pages range: 7282-7284
ISSN: 0002-7863


Abstract


In this work the rate constants (kex) and the activation parameters (ΔH, ΔS, and ΔV ) for the water exchange process on Mn centers have experimentally been determined using temperature and pressure dependent O NMR techniques. For the investigations the Mn porphyrin complexes [Mn(TPPS)S2] and [Mn (TMpyP)S2] (S = H2O and/or OH) have been selected due to their high solution stability in a wide pH range, enabling the measurements of water exchange in the case of both diaqua and aqua-hydroxo complexes. We have experimentally demonstrated that the water exchange on Mn porphyrins is a fast process (kex ≈ 10 s ) of an Id to I mechanism, strongly influenced by a Jahn-Teller effect and as such almost independent of a porphyrin charge and a trans ligand. This is also supported by our DFT calculations which show only a slight difference in an average Mn-OH2 bond found for a positively charged model porphyrin with protonated pyridine groups (2.446) and for a simple model without any substituents on the porphyrin ring (2.437). The calculated effective charge on the Mn center, which is significantly lower than its formal +3 charge (ca. +1.5 for diaqua; +1.4 for aqua-hydroxo), also contributes to its substitution lability. The herein presented results are discussed in connection to a possible fast exchanging substrate binding site in photosystem II and corresponding inorganic model complexes, as well as in the context of a possible inner-sphere catalytic pathway for superoxide dismutation on Mn centers.



FAU Authors / FAU Editors

Ivanovic-Burmazovic, Ivana Prof. Dr.
Lehrstuhl für Bioanorganische Chemie
Lieb, Dominik Dr.
Sonderforschungsbereich 583 Redoxative Metallkomplexe - Reaktivitätssteuerung durch molekulare Architekturen (Sprecher: Prof.Dr.Kisch)
Shubina, Tatyana Dr.
Sonderforschungsbereich 583 Redoxative Metallkomplexe - Reaktivitätssteuerung durch molekulare Architekturen (Sprecher: Prof.Dr.Kisch)
Zahl, Achim Dr.
Lehrstuhl für Bioanorganische Chemie


How to cite

APA:
Lieb, D., Zahl, A., Shubina, T., & Ivanovic-Burmazovic, I. (2010). Water exchange on manganese(III) porphyrins. Mechanistic insights relevant for oxygen evolving complex and superoxide dismutation catalysis. Journal of the American Chemical Society, 132(21), 7282-7284. https://dx.doi.org/10.1021/ja1014585

MLA:
Lieb, Dominik, et al. "Water exchange on manganese(III) porphyrins. Mechanistic insights relevant for oxygen evolving complex and superoxide dismutation catalysis." Journal of the American Chemical Society 132.21 (2010): 7282-7284.

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Last updated on 2019-14-04 at 21:51