Change search
ReferencesLink to record
Permanent link

Direct link
Light-induced multistep oxidation of dinuclear manganese complexes for artificial photosynthesis
Show others and affiliations
2004 (English)In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 98, no 5, 733-745 p.Article in journal (Refereed) Published
Abstract [en]

Two dinuclear manganese complexes, [Mn2BPMP(mu-OAc)(2)] . ClO4 (1, where BPMP is the anion of 2,6-bis {[N,N-di(2-pyridinemethyl)amino]methyl}-4-methylphenol) and [Mn2L(mu-OAc)(2)] . ClO4 (2, where L is the trianion of 2,6-bis{[N-(2-hydroxy-3,5-di-tert-butylbenzyl)-N-(2-pyridinemethyl)amino]methyl}-4-methylphenol), undergo several oxidations by laser flash photolysis, using ruthenium(II)-tris-bipyridine (tris(2,2-bipyridyl)dichloro-ruthenium(II) hexahydrate) as photo-sensitizer and penta-amminechlorocobalt(III) chloride as external electron acceptor. In both complexes stepwise electron transfer was observed. In 1, four Mn-valence states from the initial Mn-2(II,II) to the Mn-2(III,IV) state are available. In 2, three oxidation steps are possible from the initial Mn-2(III,III) state. The last step is accomplished in the Mn-2(IV,IV) state, which results in a phenolate radical. For the first time we provide firm spectral evidence for formation of the first intermediate state, Mn-2(II,III) in 1 during the stepwise light-induced oxidation. Observation of Mn-2(II,III) is dependent on conditions that sustain the mu-acetato bridges in the complex, i.e., by forming Mn-2(II,III) in dry acetonitrile, or by addition of high concentrations of acetate in aqueous solutions. We maintain that the presence of water is necessary for the transition to higher oxidation states, e.g., Mn-2(III,III) and Mn-2(III,IV) in 1, due to a bridging ligand exchange reaction which takes place in the Mn-2(II,III) state in water solution. Water is also found to be necessary for reaching the Mn-2(IV,IV) state in 2, which explains why this state was not reached by electrolysis in our earlier work (Eur. J. Inorg. Chem (2002) 2965). In 2, the extra coordinating oxygen atoms facilitate the stabilization of higher Mn valence states than in 1, resulting in formation of a stable Mn-2(IV,IV) without disintegration of 2. In addition, further oxidation of 2, led to the formation of a phenolate radical (g = 2.0046) due to ligand oxidation. Its spectral width (8 mT) and very fast relaxation at 15 K indicates that this radical is magnetically coupled to the Mn-2(IV,IV) center.

Place, publisher, year, edition, pages
2004. Vol. 98, no 5, 733-745 p.
Keyword [en]
manganese, photosynthesis, ruthenium, electron paramagnetic resonance, oxygen-evolving complex, water-oxidizing complex, intramolecular electron-transfer, valence mniimniii complexes, microwave-power saturation, photosystem-ii, s2yz-center-dot state, functional models, tris-bipyridine, epr signals
URN: urn:nbn:se:kth:diva-23449ISI: 000221678300010OAI: diva2:342147
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

Open Access in DiVA

No full text

In the same journal
Journal of Inorganic Biochemistry

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 14 hits
ReferencesLink to record
Permanent link

Direct link