ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
O9. Manganese- Oxo- Complexes as Water Oxidation Catalysts for
Artificial Photosynthesis
P. Kurz, H.-M. Berends, F. Tuczek
Institute for Inorganic Chemistry, Christian Albrechts University Kiel, Otto-Hahn-Platz 6/7, 24098, Kiel,
Germany
e-mail: phkurz@ac.uni-kiel.de
In nature, the oxygen evolving complex (OEC) of Photosystem II, a cluster containing four µ- oxo- bridged
manganese atoms, catalyses the four-electron oxidation of water to molecular oxygen. Our aim is to develop
water oxidation catalysts inspired by the architecture of the OEC for the construction of systems for artificial
photosynthesis.
For this purpose, we synthesise µ- oxo- bridged, dinuclear manganese complexes bearing oxidation stable
supporting ligands (see Fig. for an example). Despite numerous reports concerning the synthesis and
characterisation of such compounds, [1] studies about their interaction with water under oxidative conditions -
and especially their ability to indeed catalyse O2 formation - are rather rare.
A recent systematic screening of the reactions combinations of different manganese complexes and oxidants
indicated that a larger number of manganese complexes than known so far catalyse oxygen formation, [2] but
only if oxygen- transfer oxidants were used.
We now found that oxygen- transfer is often no prerequisite for oxygen formation any more if the manganese
complexes are fixed on surfaces (see Fig.), in agreement with a previous report.[3] The important implications of
these results for both artificial water oxidation catalysis and oxygen formation by the OEC will be presented.
Figure. left: The µ- oxo- bridged, dinuclear manganese complexes 1. right: An O2 evolution curve for the
reaction of adsorbed 1 (16µmol per g kaolin clay) with Ce 4+ (20mM). No O2 is formed for the reaction of the
clay alone or for 1 in solution.
References:
[1] Mukhopadhyay, S. et al. Chem. Rev. 104, 3981 (2004).
[2] Kurz, P. et al. Dalton Trans. 2007, 4258.
[3] Yagi, M.; Narita, K. J. Am. Chem. Soc. 126, 8084 (2004).
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