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

Eurobic9, 2-6 September, 2008, Wrocław, Poland
O11. Dioxygen Activation on a Dicopper Core with a Distorted
Coordination Environment
Y. Funahashi, K. Yoshii, T. Nishikawa, Y. Wasada-Tsutsui, Y. Kajita, T. Inomata, T. Ozawa,
and H. Masuda
Department of Applied Chemistry, Faculty of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showaku,
Nagoya 466-8555
Binding and activating dioxygen, and O-O bond formation and cleavage on dimetal centers are essentially
important for O2-transportation, catalytic oxidation, and dioxygen-evolution in biological systems. In the
biomimetic model studies of type III copper proteins, Tolman et. al clearly showed that relevant Cu2-O2 species,
µ-η 2 :η 2 -peroxo dicopper(II) and bis(µ-oxo) dicopper(III) species have the interconversion equilibrium in the
solution. In these valence isomers, the degree of O2-reduction and bond order between these oxygen atoms can
be changed, inversely.
In this study, we used (-)-sparteine (Sp) and α-isosparteine (αSp) as supporting ligands of central copper ions
with distorted coordination. The corresponding copper(I) complexes of Sp isomers reacted with O2 at �80°C to
form bis(µ oxo) dicopper(III) species, which can be transformed to a bridged and butterfly-shaped µ-η 2 :η 2 -peroxo
dicopper(II) species by addition of benzoate (OBz). After extensive studies of this system, we succeeded in
constructing a non-equilibrium Cu2-O2 system using dioxygen and hydrogen peroxide as an oxidant. The
carboxylate-bridged and butterfly-shaped µ-η 2 :η 2 -peroxo dicopper(II) species potentially has much relevance to
the reaction intermediates on stepwise O2-reduction in non-heme diiron proteins, and O2-evolving in
photosystems.
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