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Chemistry Seminar Program
Inorganic Chemistry Seminar Tuesday, March 11th Professor Yuichi Shimazaki "Synthesis and Characterization of Metal Complexes Containing Biological Molecules "  4:15pm - 5:15pm Braun Lecture Hall S.G.Mudd Chemistry Building Stanford University This seminar is free and open to the public. All Stanford University Chemistry students are encouraged to attend this special event. About the seminar We have been studying the synthesis and characterization of metal complexes of ligands incorporating components of biomolecules, such as amino acid side chain residues and porphyrins, with emphasis on the redox properties and oxidized forms of the complexes. At the seminar I would like to talk about some of our recent results. (1) O2 evolution from high-valent oxo-manganese porphyrin dimers  The oxygen evolving center (OEC) in photosystem II (PSII), which consists of a tetranuclear Mn active site, can carry out four electron oxidation of water to dioxygen. We succeeded in preparation of a high valent Mn2(V, V) species from the Mn(III, III) porphyrin dimer by addition of mCPBA under basic conditions. Each manganese ion of the high valent species has one oxo and one hydroxo group as axial ligands, and O2 evolution was detected upon addition of an acid to the solution of this species.1) (2) Characterization of the one-electron oxidized species of complexes involving a coordinated phenol or indole moiety The Cu(II)–phenoxyl radical formed during the catalytic cycle of galactose oxidase attracted much attention, and the structures and properties of a number of metal–phenoxyl radical complexes have been studied. We synthesized square-planar Cu(II), Ni(II), Pd(II), and Pt(II) complexes of the salen-type ligands and determined the valence state of one-electron oxidized complexes, which was found to depend on the central metal ion. Upon one-electron oxidation the Ni(II) complexes were converted to the Ni(II)–phenoxyl radical complexes in CH2Cl2 and to the Ni(III)–phenolate species in DMF, and the oxidation state was found to depend on the coordination properties of the solvent molecule. While the one-electron oxidized species of the Pd(II) complex was the Pd(II)–phenoxyl radical in the ground state, that of the Pt(II) complex had a large distribution of the radical electron spin at the Pt center, whose oxidation state became slightly higher than +2.2) In contrast the oxidized Cu(II)–salen complexes showed a mainly metal-centered oxidation state, which is quite different from the observation for the group 10 metal–salen complexes. On the other hand, the indole ring binds with Pd(II) and Pt(II) at C(2) position and was oxidized to give the metal(II)–indole-?-cation radical.3) These and other results will be presented and discussed. 1) Y. Shimazaki, et. al. Angew. Chem. Int. Ed. 2004, 43, 98. 2) Y. Shimazaki, et. al. J. Am. Chem. Soc. 2007, 129, 2559. 3) Y. Shimazaki, et. al. J. Am. Chem. Soc. 2004, 126, 7378. About Shimazaki: Institute for Materials Chemistry and Engineering, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan E-mail Address: yshima@ms.ifoc.kyushu.ac.jp Education and Professional Career: Ph.D., Nagoya University (Prof. Dr. Osamu Yamauchi), March, 2000 Postdoctoral Fellow, Kyushu University, April, 2000 – May, 2001 Assistant Professor, Kyushu University, June, 2001 – March, 2008 Associate Professor, Ibaraki University, April, 2008– Questions Please contact Patricia Dwyer at 650-723-4770.
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