Dioxygenases

Funabiki, Takuzo

doi:10.1007/978-94-011-5442-0_2

Cited by 14 publications

(3 citation statements)

References 376 publications

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“…Catechol dioxygenases are mononuclear nonheme enzymes playing a key role in the metabolism of aromatic compounds such as lignin and halogenated benzene in soil bacteria. − They catalyze the C−C bond cleavage of the catechol ring and are subclassified into two classes: intradiol and extradiol catechol dioxygenases. Intradiol catechol dioxygenases utilize an Fe III ion as an active center, whereas extradiol catechol dioxygenases require an Fe II ion or rarely a Mn II ion.…”

Section: Introductionmentioning

confidence: 99%

Correlation of Spin States and Spin Delocalization with the Dioxygen Reactivity of Catecholatoiron(III) Complexes

et al. 2005

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A series of catecholatoiron(III) complexes, [Fe(III)L(4Cl-cat)]BPh4 (L = (4-MeO)2TPA (1), TPA (2), (4-Cl)2TPA (3), (4-NO2)TPA (4), (4-NO2)2TPA (5); TPA = tris(pyridin-2-ylmethyl)amine; 4Cl-cat = 4-chlorocatecholate), have been characterized by magnetic susceptibility measurements and EPR, 1H NMR, and UV-vis-NIR spectroscopies to clarify the correlation of the spin delocalization on the catecholate ligand with the O2 reactivity as well as the spin-state dependence of the O2 reactivity. EPR spectra in frozen CH3CN at 123 K clearly showed that introduction of electron-withdrawing groups effectively shifts the spin equilibrium from a high-spin to a low-spin state. The effective magnetic moments determined by the Evans method in a CH3CN solution showed that 5 contains 36% of low-spin species at 243 K, while 1-4 are predominantly in a high-spin state. Evaluation of spin delocalization on the 4Cl-cat ligand by paramagnetic 1H NMR shifts revealed that the semiquinonatoiron(II) character is more significant in the low-spin species than in the high-spin species. The logarithm of the reaction rate constant is linearly correlated with the energy gap between the catecholatoiron(III) and semiquinonatoiron(II) states for the high-spin complexes 1-3, although complexes 4 and 5 deviate negatively from linearity. The lower reactivity of the low-spin complex, despite its higher spin density on the catecholate ligand compared with the high-spin analogues, suggests the involvement of the iron(III) center, rather than the catecholate ligand, in the reaction with O2.

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Section: Introductionmentioning

confidence: 99%

Correlation of Spin States and Spin Delocalization with the Dioxygen Reactivity of Catecholatoiron(III) Complexes

et al. 2005

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“…Apart from the materials interest of the iron-semiquinone complexes, a number of enzymes have been implicated to involve iron−semiquinone intermediates . The intradiol catechol dioxygenases which catalyze the cleavage of the carbon−carbon bond between the two hydroxyl groups, for example, contains non-heme iron(III) cofactor, and the catalytic cycle has been proposed to involve iron−semiquinone as an intermediate . The study of the transition metal−semiquinone complexes is, therefore, worth studying from the materials as well as bioinorganic points of view.…”

Section: Introductionmentioning

confidence: 99%

New Route to the Mixed Valence Semiquinone-Catecholate Based Mononuclear Fe^III and Catecholate Based Dinuclear Mn^III Complexes: First Experimental Evidence of Valence Tautomerism in an Iron Complex

et al. 2004

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The semiquinone-catecholate based mixed valence complex, [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] x DMF (1), and catecholate based (H2bispictn)[Mn2III(Cl4Cat)4(DMF)2] (2) (bispicen = N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine, bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, Cl4Cat = tetrachlorocatecholate dianion, and Cl4SQ = tetrachlorosemiquinone radical anion) were synthesized directly utilizing a facile route. Both the complexes have been characterized by single crystal X-ray diffraction study. The electronic structures have been elucidated by UV-vis-NIR absorption spectroscopy, cyclic voltammetry, EPR, and magnetic properties. The structural as well as spectroscopic features support the mixed valence tetrachlorosemiquinone-tetrachlorocatecholate charge distribution in 1. The ligand based mixed valence state was further confirmed by the presence of an intervalence charge transfer (IVCT) band in the 1900 nm region both in solution and in the solid. The intramolecular electron transfer, a phenomenon known as valence tautomerism (VT), has been followed by electronic absorption spectroscopy. For 1, the isomeric form [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] is favored at low temperature, while at an elevated temperature, the [FeII(bispicen)(Cl4SQ)2] redox isomer dominates. Infrared as well as UV-vis-NIR spectral characterization for 2 suggest that the MnIII(Cat)2- moiety is admixed with its mixed valence semiquinone-catecholate isomer MnII(SQ)(Cat)-, and the electronic absorption spectrum is dominated by the mixed charged species. The origin of the intervalence charge transfer band in the 1900 nm range is associated with the mixed valence form, MnII(Cl4Cat)(Cl4SQ)-. The observation of VT in complex 1 is the first example where a mixed valence semiquinone-catecholate iron(III) complex undergoes intramolecular electron transfer similar to manganese and cobalt complexes.

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“…In nature, a variety of organic compounds can be oxidized easily by molecular oxygen or other oxygen donors in the cells of bacteria, fungi, plants, insects, fish, and mammals (24)(25)(26). It is worth noting the important advances in biomimetic approaches to such oxidations (27)(28)(29)(30)(31)(32)(33)(34)(35)(36). Hydroxylation of linear alkanes or methane to generate terminal alcohols is very useful in the synthesis of chemicals and fuels (37).…”

Section: Direct Conversion Of C-h Bondsmentioning

confidence: 99%

Green chemistry for chemical synthesis

Trost²

2008

Proc. Natl. Acad. Sci. U.S.A.

830

360

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Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize by-products, designing new synthetic schemes and apparati that can simplify operations in chemical productions, and seeking greener solvents that are inherently environmentally and ecologically benign.

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Dioxygenases

Cited by 14 publications

References 376 publications

Correlation of Spin States and Spin Delocalization with the Dioxygen Reactivity of Catecholatoiron(III) Complexes

Correlation of Spin States and Spin Delocalization with the Dioxygen Reactivity of Catecholatoiron(III) Complexes

New Route to the Mixed Valence Semiquinone-Catecholate Based Mononuclear Fe^III and Catecholate Based Dinuclear Mn^III Complexes: First Experimental Evidence of Valence Tautomerism in an Iron Complex

Green chemistry for chemical synthesis

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Dioxygenases

Cited by 14 publications

References 376 publications

Correlation of Spin States and Spin Delocalization with the Dioxygen Reactivity of Catecholatoiron(III) Complexes

Correlation of Spin States and Spin Delocalization with the Dioxygen Reactivity of Catecholatoiron(III) Complexes

New Route to the Mixed Valence Semiquinone-Catecholate Based Mononuclear FeIII and Catecholate Based Dinuclear MnIII Complexes: First Experimental Evidence of Valence Tautomerism in an Iron Complex

Green chemistry for chemical synthesis

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New Route to the Mixed Valence Semiquinone-Catecholate Based Mononuclear Fe^III and Catecholate Based Dinuclear Mn^III Complexes: First Experimental Evidence of Valence Tautomerism in an Iron Complex