| 14514302 |
Triller MU, Pursche D, Hsieh WY, Pecoraro VL, Rompel A, Krebs B: Catalytic oxidation of 3,5-Di-tert-butylcatechol by a series of mononuclear manganese complexes: synthesis, structure, and kinetic investigation. Inorg Chem. 2003 Oct 6;42(20):6274-83.
The manganese compounds [Mn (bpia)(OAc)(OCH (3))](PF (6)) (1), [Mn (bipa)(OAc)(OCH (3))](PF (6)) (2), [Mn (bpia)(Cl)(2)](ClO (4)) (3), [Mn (bipa)(Cl)(2)](ClO (4)) (4), [Mn (Hmimppa)(Cl)(2)] x CH (3) OH (5), and [Mn (mimppa)(TCC)] x 2CHCl (3) (6) (bpia = bis (picolyl)(N-methylimidazole-2-yl) amine; bipa = bis (N-methylimidazole-2-yl)(picolyl) amine; Hmimppa = ((1-methylimidazole-2-yl) methyl)((2-pyridyl) methyl)(2-hydroxyphenyl) amine; TCC = tetrachlorocatechol) were synthesized and characterized by various techniques such as X-ray crystallography, mass spectrometry, IR, EPR, and UV/vis spectroscopy, cyclic voltammetry, and elemental analysis. 1 and 2 crystallize in the triclinic space group Ponemacr; (No. 2), 4 and 6 crystallize in the monoclinic space group P2 (1)/n (No. 14), and 5 crystallizes in the orthorhombic space group Pna2 (1). Complexes 1-4 are structurally related to the proposed active site of the manganese-dependent extradiol-cleaving catechol dioxygenase exhibiting an N (4) O (2) donor set (1 and 2) or N (4) Cl (2) donor set (3 and 4). Cyclic voltammetric data show that the substitution of oxygen donor atoms with chloride causes a shift of redox potentials to more positive values. These compounds show high catalytic activity regarding the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone exhibiting saturation kinetics at high substrate concentrations. The turnover numbers k (cat) = (86 +/- 7) h (-1) (1), k (cat) = (101 +/- 4) h (-1) (2), k (cat) = (230 +/- 4) h (-1) (3), and k (cat) = (130 +/- 4) h (-1) (4) were determined from the double reciprocal Lineweaver-Burk plot. Compounds 5 and 6 can be regarded as structural and electronic Mn analogues for substituted forms of Fe-containing intradiol-cleaving catechol dioxygenases. To our knowledge 5 is the first mononuclear Mn (II) compound featuring an N (3) OCl (2) donor set. |
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