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This article has been retracted as it is essentially identical in content with a previously published paper: Inorganic Chemistry 2002, Volume 41, Issue number 24, pp 6258-6266 (American Chemical Society, ACS Publications). In particular, the article contains identical figures (namely figures 4b, 5a, and 5b) with the above mentioned paper. While in the earlier published paper, the figures described the Ru-complex attached to TiO2, the same figures have now been used in this article to describe the electron transfer between the Ru-complex and the SnO2 semiconductor.

International Journal of Photoenergy
Volume 2008, Article ID 524142, 7 pages
Research Article

Light-Induced Tyrosine Radical Formation from Ruthenium-Tyrosine Complex Anchored to SnO2 Semiconductor

Department of Chemistry, University of Al al-Bayt, P.O. Box 130040, Mafraq 25113, Jordan

Received 4 August 2007; Revised 26 October 2007; Accepted 10 December 2007

Academic Editor: Panagiotis Lianos

Copyright © 2008 Raed Ghanem. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Steady state spectroscopy and flash photolysis measurements were used to study the multistep electron transfer in a supramolecular complex adsorbed on the surface of nanocrystalline S n O 2 in order to mimic the function of the tyrosineZ and chlorophyll unit P 6 8 0 in natural photosystem II (PSII). A ruthenium(II)-tris(bipyridyl) complex covalently linked to an L-tyrosine ethyl ester through an amide bond was anchored to the surface of nanocrystalline S n O 2 via four carboxylic acid groups linked to the bpy ligands. The apparent association constant for the association between ruthenium(II)-tris(bipyridyl) complex and S n O 2 is 3 . 2 × 1 0 6 M 1 and a degree of association up to 99% was determined. 450 nm excitation of the complex promotes an electron to a metal-to-ligand charge transfer (MLCT) excited state, from which the electron is injected into S n O 2 . The photogeneration of Ru(III) is followed by an intramolecular electron transfer from tyrosine to Ru(III), regenerating the photosensitizer Ru(II) and forming the tyrosyl radical. The tyrosyl radical is formed in less than 3 microseconds with a yield of 32%.