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

Eurobic9, 2-6 September, 2008, Wrocław, Poland
O28. Enzyme-like Oxygenation and Oxidation of Catechols with Molecular
Oxygen via Mn(II)-Semiquinonate Complexes
T. Funabiki, E. Tanigawa, M. Shimomaki, A. Mochizuki, K. Teramaoto, Y. Hitomi,
M. Kodera
Department of Molecular Chemistry and Biochemistry, Doshisha University, Tatara, 610-0321, Kyotanabe,
Japan
e-mail: funabiki@m3.dion.ne.jp
We have developed a new Mn(II)-semiquinone complex, [Mn(L)(DTBSQ)] + (1, DTBSQ: 3, 5-di-tert-butyl-1, 2benzosemiquinonate,
L: TPA), which is analogous to the intermediate species, Fe(II)-semiquinonate, proposed in
the oxygenations by Fe 3+ -intradiol catechol dioxygenases. UV-VS and ESI/MS spectroscopies of the solution of
1 after the alternate O2 and Ar babblings suggested the intermediaate formation of [Mn(L)(DTBSQ)(O2)] + (2). In
case of alcoholic solvents, intradiol oxygenation products were obtained, indicating that oxygen attached to
Mn(II) in 2 reacts with the semiquinonate ligand to give intradiol oxygenation products. In acetonitrile, quinone,
DTBQ, was selectively formed, and a m-oxo-dimer, [Mn(L)(m-O)]2 2+ (3), was isolated as an intermediate [1]. In
the presence of the excess catehol, DTBCH2, DTBQ was catalytically formed. Noteworthily, O2 is reduced to
H2O similarly to the enzyme system, while in the most model studies for catechol oxidases O2 is reduced to
H2O2. The oxidation system was applied to catechols other than DTBCH2, but 3 was used as the starting
complex in place of semiqunonate complexes which could not be prepared by the same way applied to 1. When
4-t-Butylcatechol (TBCH2), 4-methylcatechol (MeCH2), and pyrocatechol (HCH2) were added to 3, peaks
characteristic to the Mn(II)-semiquinonate complexes were first observed, followed by the peaks for quinones.
The reactivity was in the order DTBCH2 > TBCH2 > MeCtH2 > HCH2
References:
[1] Y. Hitomi, A. Ando, H. Matsui, T. Ito, T. Tanaka, S. Ogo, T. Funabiki, Inorg. Chem. 2005, 44, 3473-8.
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