Electron Transfer by Copper Centers

Rorabacher, D. B.

doi:10.1021/cr020630e

Cited by 412 publications

(410 citation statements)

References 202 publications

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“…The covalent capping effect of the tren associated with its strong chelate effect tightly ensures a trigonal coordination geometry for Cu in both redox states. The reorganization at the Cu(II)͞Cu(I) process remains limited to the unbinding͞binding of the axial guest (14,56). This on͞off guest binding process in the calixarene pocket can be electrochemically controlled.…”

Section: Discussionmentioning

confidence: 99%

“…Most classical models, however, irreversibly lead to dinuclear species because of the propensity of reactive cupric species to undergo dimerization (7)(8)(9)(10). Trying to gain insights into the chemical and redox specificity (11)(12)(13)(14)(15) resulting from the proteic environment of mono-copper sites, we have developed a supramolecular system that mimics not only the polyhistidine binding core but also the hydrophobic pocket that controls the second coordination sphere of the metal and its binding to an exogenous molecule. The model is based on a calix [6]arene functionalized with a nitrogenous coordination core (16 -24).…”

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confidence: 99%

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Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Izzet

Douziech

Prangé

et al. 2005

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

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Mono-copper enzymes play an important role in biology and their functionality is based on Cu(II)͞Cu(I) redox processes. Modeling a mono-nuclear site remains a challenge for a better understanding of its intrinsic reactivity. The first member of a third generation of calixarene-based mono-copper ''funnel'' complexes is described. The ligand is a calix[6]arene capped by a tren unit, hence presenting a N4 coordination site confined in a cavity. Its Cu(II) complexes were characterized by electronic and EPR spectroscopies. The x-ray structure of one of them shows a five-coordinated metal ion in a slightly distorted trigonal bipyramidal geometry thanks to its coordination to a guest ligand L (ethanol). The latter sits in the heart of the hydrophobic calixarene cone that mimics the active site chamber and the hydrophobic access channel of enzymes. bioinorganic ͉ supramolecular ͉ electrochemistry ͉ host-guest ͉ enzyme model C opper enzymes such as dopamine ␤-monooxygenase, peptidylglycine ␣-hydroxylating monooxygenase, and nitrate reductase present a mononuclear copper ion buried in their active pocket opened to the external medium through a selective substrate access channel. This organization is responsible for the efficiency and selectivity of their catalytic activity (1-6). A good chemical model for metalloenzymes is a key to the understanding of the fundamental mechanisms involved in the catalytic cycle and to the design of efficient and selective new tools for the synthetic chemist. Most classical models, however, irreversibly lead to dinuclear species because of the propensity of reactive cupric species to undergo dimerization (7-10). Trying to gain insights into the chemical and redox specificity (11-15) resulting from the proteic environment of mono-copper sites, we have developed a supramolecular system that mimics not only the polyhistidine binding core but also the hydrophobic pocket that controls the second coordination sphere of the metal and its binding to an exogenous molecule. The model is based on a calix[6]arene functionalized with a nitrogenous coordination core (16 -24). The first generation of such ligands (calix[6]N 3 , see Fig. 1) (16, 17) presents three amino arms that, upon binding to the copper ion, constrain the calix[6]arene into the cone conformation required to play the role of a host for a guest ligand L. The so-called funnel complexes best stabilize Cu(I) in a tetrahedral N 3 L environment (16, 18 -20), whereas the Cu(II) species adopt a square-based pyramidal geometry N 3 L(S) with the binding of a water molecule (S is H 2 O) as a fifth ligand that is added to the system by an upper access from the outside (21,22). Despite the coordination number change between both redox states, the calixarene cavity acts as a selective funnel for small neutral organic molecules (L) as a result of the innercavity coordination site. Interestingly, the guest ligand L was shown to play the role of a shoetree molecule (23, 24) that shapes the calixarene structure and fixes the global organization of the co...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Izzet

Douziech

Prangé

et al. 2005

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

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“…Fe-S and blue copper proteins). 13 Many of these sites feature multiple H-bonding interactions between the ligated sulfur atoms and the protein backbone NH groups. H-bonding interactions along with other factors e.g.…”

Section: Introductionmentioning

confidence: 99%

Sulfur K-Edge XAS and DFT Calculations on P450 Model Complexes: Effects of Hydrogen Bonding on Electronic Structure and Redox Potentials

et al. 2005

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Hydrogen bonding is generally thought to play an important role in tuning the electronic structure and reactivity of metal-sulfur sites in proteins. To develop a quantitative understanding of this effect, S K-edge X-ray absorption spectroscopy (XAS) has been employed to directly probe ligand-metal bond covalency, where it has been found that protein active sites are significantly less covalent than their related model complexes. Sulfur K-edge XAS data are reported here on a series of P450 model complexes with increasing H-bonding to the ligated thiolate from its substituent. The XAS spectroscopic results show a dramatic decrease in pre-edge intensity. DFT calculations reproduce these effects and show that the observed changes are in fact solely due to H-bonding and not from the inductive effect of the substituent on the thiolate. These calculations also indicate that the Hbonding interaction in these systems is mainly dipolar in nature. The −2.5 kcal/mole energy of the H-bonding interaction was small relative to the large change in ligand-metal bond covalency (30%) observed in the data. A bond decomposition analysis of the total energy is developed to correlate the pre-edge intensity change to the change in Fe-S bonding interaction on H-bonding. This effect is greater for the reduced than the oxidized state, leading to a 330 mV increase in the redox potential. A simple model shows that E° should vary approximately linearly with the covalency of the Fe-S bond in the oxidized state, which can be determined directly from S K-edge XAS.

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“…Each copper atom is part of a five-membered chelate ring with a S-Cu-N angle of 88.68 (average). The S-Cu-S angles vary more and are 151.5(2), 145.6(2), and 126.5(2)8 for Cu (11), Cu (13), and Cu (12) 2+ (2), which could be isolated as the hexafluorophosphate salt. This cation formally represents the dimeric variant of the oxidized trinuclear compound 1 + ( Figure 5).…”

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confidence: 99%

The Trinuclear Copper(I) Thiolate Complexes[Cu₃(NGuaS)₃]^0/1+ and their Dimeric Variants [Cu₆(NGuaS)₆]^1+/2+/3+ with Biomimetic Redox Properties

et al. 2011

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Electron Transfer by Copper Centers

Cited by 412 publications

References 202 publications

Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Sulfur K-Edge XAS and DFT Calculations on P450 Model Complexes: Effects of Hydrogen Bonding on Electronic Structure and Redox Potentials

The Trinuclear Copper(I) Thiolate Complexes[Cu₃(NGuaS)₃]^0/1+ and their Dimeric Variants [Cu₆(NGuaS)₆]^1+/2+/3+ with Biomimetic Redox Properties

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Electron Transfer by Copper Centers

Cited by 412 publications

References 202 publications

Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Sulfur K-Edge XAS and DFT Calculations on P450 Model Complexes: Effects of Hydrogen Bonding on Electronic Structure and Redox Potentials

The Trinuclear Copper(I) Thiolate Complexes[Cu3(NGuaS)3]0/1+ and their Dimeric Variants [Cu6(NGuaS)6]1+/2+/3+ with Biomimetic Redox Properties

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The Trinuclear Copper(I) Thiolate Complexes[Cu₃(NGuaS)₃]^0/1+ and their Dimeric Variants [Cu₆(NGuaS)₆]^1+/2+/3+ with Biomimetic Redox Properties