Catalytic Oxidation of 3,5-Di-tert-butylcatechol by a Series of Mononuclear Manganese Complexes: Synthesis, Structure, and Kinetic Investigation
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- 作者：Michael U. Triller ; Daniel Pursche ; Wen-Yuan Hsieh ; Vincent L. Pecoraro ; Annette Rompel ; and Bernt Krebs
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：October 6, 2003
- 年：2003
- 卷：42
- 期：20
- 页码：6274 - 6283
- 全文大小：206K
- 年卷期：v.42,no.20(October 6, 2003)
- ISSN：1520-510X
文摘
The manganese compounds [Mn(bpia)(OAc)(OCH3)](PF6) (1), [Mn(bipa)(OAc)(OCH3)](PF6) (2), [Mn(bpia)(Cl)2](ClO4)(3), [Mn(bipa)(Cl)2](ClO4) (4), [Mn(Hmimppa)(Cl)2]·CH3OH (5), and [Mn(mimppa)(TCC)]·2CHCl3 (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 synthesizedand characterized by various techniques such as X-ray crystallography, mass spectrometry, IR, EPR, and UV/visspectroscopy, cyclic voltammetry, and elemental analysis. 1 and 2 crystallize in the triclinic space group P
(No.2), 4 and 6 crystallize in the monoclinic space group P21/n (No. 14), and 5 crystallizes in the orthorhombic spacegroup Pna21. Complexes 1-4 are structurally related to the proposed active site of the manganese-dependentextradiol-cleaving catechol dioxygenase exhibiting an N4O2 donor set (1 and 2) or N4Cl2 donor set (3 and 4). Cyclicvoltammetric data show that the substitution of oxygen donor atoms with chloride causes a shift of redox potentialsto 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 turnovernumbers kcat = (86 ± 7) h-1 (1), kcat = (101 ± 4) h-1 (2), kcat = (230 ± 4) h-1 (3), and kcat = (130 ± 4) h-1 (4)were determined from the double reciprocal Lineweaver-Burk plot. Compounds 5 and 6 can be regarded as structuraland electronic Mn analogues for substituted forms of Fe-containing intradiol-cleaving catechol dioxygenases. Toour knowledge 5 is the first mononuclear Mn(II) compound featuring an N3OCl2 donor set.
(No.2), 4 and 6 crystallize in the monoclinic space group P21/n (No. 14), and 5 crystallizes in the orthorhombic spacegroup Pna21. Complexes 1-4 are structurally related to the proposed active site of the manganese-dependentextradiol-cleaving catechol dioxygenase exhibiting an N4O2 donor set (1 and 2) or N4Cl2 donor set (3 and 4). Cyclicvoltammetric data show that the substitution of oxygen donor atoms with chloride causes a shift of redox potentialsto 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 turnovernumbers kcat = (86 ± 7) h-1 (1), kcat = (101 ± 4) h-1 (2), kcat = (230 ± 4) h-1 (3), and kcat = (130 ± 4) h-1 (4)were determined from the double reciprocal Lineweaver-Burk plot. Compounds 5 and 6 can be regarded as structuraland electronic Mn analogues for substituted forms of Fe-containing intradiol-cleaving catechol dioxygenases. Toour knowledge 5 is the first mononuclear Mn(II) compound featuring an N3OCl2 donor set.