Photo-induced oxidation of a dinuclear Mn-2(II,II) complex to the Mn-2(III,IV) state by inter- and intramolecular electron transfer to Ru-III tris-bipyridine
2002 (English)In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 91, no 1, 159-172 p.Article in journal (Refereed) Published
To model the structural and functional parts of the water oxidizing complex in Photosystem 11, a dimeric manganese(II,11) complex (1) was linked to a ruthenium(II)tris-bipyridine (Ru-II(bpy)3) complex via a substituted L-tyrosine, to form the trinuclear complex 2 [J. Inorg. Biochem. 78 (2000) 15]. Flash photolysis of 1 and Ru-II(bpy), in aqueous solution, in the presence of an electron acceptor, resulted in the stepwise extraction of three electrons by Ru-III(bpy), from the Mn-2(II,II) dimer, which then attained the Mn-2(III,IV) oxidation state. In a similar experiment with compound 2, the dinuclear Mn complex reduced the photo-oxidized Ru moiety via intramolecular electron transfer on each photochemical event. From EPR it was seen that 2 also reached the Mn-2(III,IV) state. Our data indicate that oxidation from the Mn-2(II,II) state proceeds stepwise via intermediate formation of Mn-2(II,III) and Mn-2(III,III). In the presence of water, cyclic voltammetry showed an additional anodic peak beyond Mn-2(II,III/III,III) oxidation which was significantly lower than in neat acetonitrile. Assuming that this peak is due to oxidation to Mn-2(III,IV), this suggests that water is essential for the formation of the Mn-2(III,IV) oxidation state. Compound 2 is a structural mimic of the water oxidizing complex, in that it links a Mn complex via a tyrosine to a highly oxidizing photosensitizer. Complex 2 also mimics mechanistic aspects of Photosystem 11, in that the electron transfer to the photosensitizer is fast and results in several electron extractions from the Mn moiety.
Place, publisher, year, edition, pages
2002. Vol. 91, no 1, 159-172 p.
manganese, EPR spectroscopy, electrochemistry, artificial photosynthesis, bioinorganic chemistry, valence mniimniii complexes, photosystem-ii, manganese complexes, different solvents, water oxidation, catalase, tyrosine, models, epr, ruthenium
IdentifiersURN: urn:nbn:se:kth:diva-21764ISI: 000177141500019OAI: oai:DiVA.org:kth-21764DiVA: diva2:340462
QC 201005252010-08-102010-08-10Bibliographically approved