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Characterization and mechanistic inv...

Mirica, Liviu M.

Characterization and mechanistic investigations of model complexes relevant to binuclear and multinuclear copper enzymes.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Characterization and mechanistic investigations of model complexes relevant to binuclear and multinuclear copper enzymes.
作者:	Mirica, Liviu M.
面頁冊數:	250 p.
附註:	Adviser: T. Daniel P. Stack.
附註:	Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0275.
Contained By:	Dissertation Abstracts International66-01B.
標題:	Chemistry, Inorganic.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3162369
ISBN:	0496963600

Characterization and mechanistic investigations of model complexes relevant to binuclear and multinuclear copper enzymes.
Mirica, Liviu M.

Characterization and mechanistic investigations of model complexes relevant to binuclear and multinuclear copper enzymes. - 250 p.

Adviser: T. Daniel P. Stack.

Thesis (Ph.D.)--Stanford University, 2005.

Further investigation of the tyrosinase-like reactivity at extreme temperatures (-120°C) allowed the detection for the first time of several intermediates during the hydroxylation reaction. Based on detailed spectroscopic characterization (UV-Vis, resonance Raman, X-ray absorption spectroscopy), a bis-mu-oxodicopper(III)-phenolate structure is proposed as the active hydroxylating agent. This complex appears to be a competent oxidant in the hydroxylation of phenols and the reaction has all the hallmarks of an electrophilic aromatic substitution, akin to tyrosinase. In the hydroxylation reaction performed by this model complex, O-O bond cleavage occurs before the C-O bond-forming step.

ISBN: 0496963600Subjects--Topical Terms:

197298
Chemistry, Inorganic.

Characterization and mechanistic investigations of model complexes relevant to binuclear and multinuclear copper enzymes.
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100 0 $a Mirica, Liviu M. $3 237460
245 1 0 $a Characterization and mechanistic investigations of model complexes relevant to binuclear and multinuclear copper enzymes.
300 $a 250 p.
500 $a Adviser: T. Daniel P. Stack.
500 $a Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0275.
502 $a Thesis (Ph.D.)--Stanford University, 2005.
520 # $a Further investigation of the tyrosinase-like reactivity at extreme temperatures (-120°C) allowed the detection for the first time of several intermediates during the hydroxylation reaction. Based on detailed spectroscopic characterization (UV-Vis, resonance Raman, X-ray absorption spectroscopy), a bis-mu-oxodicopper(III)-phenolate structure is proposed as the active hydroxylating agent. This complex appears to be a competent oxidant in the hydroxylation of phenols and the reaction has all the hallmarks of an electrophilic aromatic substitution, akin to tyrosinase. In the hydroxylation reaction performed by this model complex, O-O bond cleavage occurs before the C-O bond-forming step.
520 # $a In a separate study, a tris(mu-hydroxy)tricopper(II) complex was shown to self-assemble from the reaction of the copper(I) complex of DBED and dioxygen. This complex is a structural model of the proposed native intermediate in multicopper oxidases (i.e. laccase, ascorbate oxidase), and one of the simplest case of a spin frustrated system, with three Cu(II) S = 1/2 centers bridged by single atom hydroxide ligands. Additionally, an interesting effect of weakly coordinating counteranions on the nuclearity of the copper complexes formed in solution was observed.
520 # $a The biological role of copper in oxidative processes that involve O2 activation is critical to aerobic life. In tyrosinase, a binuclear copper enzyme, a mu-eta2:eta2-peroxodicopper(II) (P) species is proposed to be the active oxidant in the hydroxylation of phenols to catechols and the oxidation of catechols to quinones. Synthetic model complexes have been critical in studying the structure-reactivity relationships of copper enzymes. It was shown in our laboratory that bidentate ligation of peralkylated diamine ligands to Cu(I) is sufficient to allow O2 activation to yield either a pure bis-mu-oxodicopper(III) species ( O) or an equilibrium mixture of the isoelectronic P and O species. A P complex stable at -80°C that employs a bidentate secondary diamine ligand N,N '-di-tert-butyl-ethylenediamine (DBED) is reported. The spectroscopic characteristics of this complex prove to be strongly dependent on the counteranion employed, suggesting an intimate interaction of the counteranions with the Cu-O2 cores. This new complex exhibits hydroxylation reactivity by converting phenolates to catechols, proving to be a functional model of tyrosinase.
520 # $a The investigations performed on synthetic models have been complemented by density functional theory (DFT). Hybrid DFT methods provide the most computationally efficient method and were calibrated to attain a good correlation with the experimental results. The relative energies of the P and O species were calculated and suggest that these two species can interconvert easily. In a biologically relevant environment, like in tyrosinase, the O species was calculated to be easily accessible and cannot be excluded as a possible intermediate in the hydroxylation of phenols, as concluded in previous studies.
520 # $a Theoretical calculations were employed in calculating the hydroxylation reaction coordinate, supporting the experimental observation that the bis-mu-oxodicopper(III)-phenolate complex is capable of electrophilic phenol hydroxylation. All results provide insights into the mechanism of tyrosinase, where the intermediacy of a bis-mu-oxodicopper(III) species cannot be excluded. The potential role of such species in biological oxidation reactions remains an intriguing question.
590 $a School code: 0212.
650 # 0 $a Chemistry, Inorganic. $3 197298
690 $a 0488
710 0 # $a Stanford University. $3 212607
773 0 # $g 66-01B. $t Dissertation Abstracts International
790 $a 0212
790 1 0 $a Stack, T. Daniel P., $e advisor
791 $a Ph.D.
792 $a 2005
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