Structural and Electrochemical Comparison of Copper(II) Complexes with Tripodal Ligands

Nagao, Hidemi; Komeda, Nobutoshi; Mukaida, Masao; Suzuki, Masatatsu; Tanaka, Koji

doi:10.1021/ic960303n

Cited by 183 publications

(213 citation statements)

References 47 publications

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“…[{(C 2 H 4 ) 2 Rh(m-Cl)} 2 ], [42] and the ligands TPA [43] and MeTPA [44] were prepared according to literature procedures. All other chemicals are commercially available and were used without further purification, unless stated otherwise.…”

Section: Discussionmentioning

confidence: 99%

2-Rhodaoxetanes: Their Formation of Oxidation of [RhI(ethene)]+ and Their Reactivity upon Protonation

et al. 2000

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New cationic, pentacoordinate complexes [(TPA)Rh1(ethene)]+, [1a]+, and [(MeTPA)Rh1(ethene)]+, [1b]+, have been prepared (TPA = N,N,N-tri(2-pyridylmethyl)amine, MeTPA = N-[(6-methyl-2-pyridyl)-methyl]-N,N-di(2-pyridylmethyl)amine). Complex [1a]+ is selectively converted by aqueous HCl to [(TPA)RhIII-(ethyl)Cl]+, [2a]+. The same reaction with [1b]+ results in the [(MeTPA)RhIII-(ethyl)Cl]+ isomers [2b]+ and [2c]+. Treatment of [1a]+ and [1b]+ with aqueous H2O2 results in a selective oxygenation to the unsubstituted 2-rho-da(III)oxetanes (1-oxa-2-rhoda(III)cyclo-butanes) [(TPA)RhIII(kappa2-C,O-2-oxyethyl)]+, [3a]+, and [(MeTPA)RhIII(kappa2-C,O-2-oxyethyl)]+, [3b]+. The reactivity of 2-rhodaoxetanes [3a]+ and [3b]+ is dominated by the nucleophilic character of their 2-oxyethyl oxygen. Reaction of [3a]+ and [3b]+ with the non-coordinating acid HBAr(f)4 results in the dicationic protonated 2-rhodaoxetanes [(TPA)RhIII(kappa2-2-hydroxyethyl)]2+, [4a]2+, and [(MeTPA)RhIII(kappa2-2-hydroxyethyl)]2+, [4b]2+. These eliminate acetaldehyde at room temperature, probably via a coordinatively unsaturated kappa1-2-hydroxyethyl complex. In acetonitrile, complex [4a]2+ is stabilised as [(TPA)-RhIII(kappa1-2-hydroxyethyl)(MeCN)]2+, [5a]2+, whereas the MeTPA analogue [4b]2+ continues to eliminate acetaldehyde. Reaction of [3a]+ with NH4Cl and Mel results in the coordinatively saturated complexes [(TPA)RhIII(kappa1-2-hydroxyethyl)(Cl)]+, [6a]+, and [(TPA)-RhIII(kappa1-2-methoxyethyl)(I)+, [7a]+, respectively. Reaction of [3a]+ with NH4+ in MeCN results in formation of the dicationic metallacyclic amide [(TPA)-RhIII [kappa2-O,C-2-(acetylamino)ethyl]]2+, [9]2+, via the intermediates [4a]2+, [5a]2+ and the metallacyclic iminoester [(TPA)RhIII[kappa2-N,C-2-(acetimidoyloxy)ethyl]]2+, [8]2+. The observed overall conversion of the [Rh(I)(ethene)] complex [1a]+ to the metallacyclic amide [9]2+ via 2-rhodaoxetane [3a]+, provides a new route for the amidation of a [RhI(ethene)] fragment.

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Section: Discussionmentioning

confidence: 99%

2-Rhodaoxetanes: Their Formation of Oxidation of [RhI(ethene)]+ and Their Reactivity upon Protonation

et al. 2000

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“…Numerous other mononuclear models that examine NiR reactivity have been explored so far (31,36,(47)(48)(49)(50). These compounds are split into those whose activities have been investigated in nonaqueous solutions (34,49,50) and those that have been examined in aqueous solutions (47,48,(51)(52)(53)(54). In the case of nonaqueous systems, the reaction rates are higher than those observed in aqueous solutions, and the ligands in some cases model the tris-His environment of NiR relatively well (9,49,50).…”

mentioning

confidence: 99%

“…There are only a few examples of functional copper complexes that can reduce nitrite in aqueous solutions, and in general these systems have far lower rates that those observed in nonaqueous conditions. In some cases, these complexes produced N 2 O rather than NO (48, 54), whereas the systems in which multiple turnovers were observed have been associated mostly with electrocatalytic reactions, particularly heterogeneous systems (i.e., catalyst linked to the electrode surface) (47,48,51,54). One example has been reported of a copper complex capable of at least four turnovers in 15 min when reduced using photoactivated [Ru(II)(bpy) 3 ] 2+ as the electron donor, but with a significant decrease in activity (NO generation) after two turnovers (52).…”

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confidence: 99%

Designing a functional type 2 copper center that has nitrite reductase activity within α-helical coiled coils

Tegoni

Yu²,

Bersellini

et al. 2012

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

101

188

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One of the ultimate objectives of de novo protein design is to realize systems capable of catalyzing redox reactions on substrates. This goal is challenging as redox-active proteins require design considerations for both the reduced and oxidized states of the protein. In this paper, we describe the spectroscopic characterization and catalytic activity of a de novo designed metallopeptide Cu(I/II)(TRIL23H) 3 +/2+ , where Cu(I/II) is embeded in α-helical coiled coils, as a model for the Cu T2 center of copper nitrite reductase. In Cu(I/II)(TRIL23H) 3 +/2+ , Cu(I) is coordinated to three histidines, as indicated by X-ray absorption data, and Cu(II) to three histidines and one or two water molecules. Both ions are bound in the interior of the three-stranded coiled coils with affinities that range from nano- to micromolar [Cu(II)], and picomolar [Cu(I)]. The Cu(His) 3 active site is characterized in both oxidation states, revealing similarities to the Cu T2 site in the natural enzyme. The species Cu(II)(TRIL23H) 3 2+ in aqueous solution can be reduced to Cu(I)(TRIL23H) 3 + using ascorbate, and reoxidized by nitrite with production of nitric oxide. At pH 5.8, with an excess of both the reductant (ascorbate) and the substrate (nitrite), the copper peptide Cu(II)(TRIL23H) 3 2+ acts as a catalyst for the reduction of nitrite with at least five turnovers and no loss of catalytic efficiency after 3.7 h. The catalytic activity, which is first order in the concentration of the peptide, also shows a pH dependence that is described and discussed.

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“…As shown in figure 4a, cluster 1 shows a pair of redox peaks with a cathodic peak potential (E pc ) at 0.485 V and an anodic peak potential (E pa ) at 0.767 V. The half-wave potential (E 1/2 = 1/2(E pa + E pc )) and the peak-to-peak potential separation (ΔE p ) were obtained as 0.626 V and 0.282 V, respectively, indicating that the electrochemical behavior of 1 is quasi-reversible corresponding to the redox process of all four copper (Cu(II)/Cu(I)). [39][40][41] The crystal structures of complex 1 plexes have similar structures, namely a tetranuclear cluster containing four Cu, one μ 4 -O, six μ 2 -X atoms (X = Cl, 1 and Br, 2), and four pyrazole ligands. The electrochemical behavior of clusters 1 and 2 are quasi-reversible corresponding to the redox process of all four copper (Cu(II)/Cu(I)).…”

Section: Cyclic Voltammetrymentioning

confidence: 99%

Synthesis, Structure and Electrochemistry of Tetranuclear Oxygen-Centered Copper(II) Clusters with Acetylacetone and Benz-pyrazole Hydrolyzed Derivatives as Ligand

Vafazadeh

Willis²

2016

ACSi

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Two copper(II) clusters Cu 4 OCl 6 (pyrazole) 4 (1) and Cu 4 OBr 6 (Br-pyrazole) 4 (2) have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio) with CuX 2 (X = Cl for 1 and X = Br for 2) in methanol solution. The structures of both clusters have been established by X-ray crystallography. The clusters contain four Cu, one O, six μ 2 -X atoms, and four pyrazole ligands. The pyrazole was prepared in situ by the reaction of acetylacetone with benzohydrazide in methanol under reflux. In 2, the methine hydrogen of the pyrazole ligand has been replaced by bromine atom. The four copper atoms encapsulate the central O atom in a tetrahedral arrangement. All copper atoms are five-coordinate and have similar coordination environments with slightly distorted trigonal bipyramidal geometry. The cyclic voltammogram of the clusters 1 and 2 show a one-electron quasi-reversible reduction wave in the region 0.485 to 0.731 V, and a one-electron quasi-reversible oxidation wave in the region 0.767 to 0.898 V. In 1, one irreversible oxidative response is observed on the positive of side of the voltammogram at 1.512 V and this can be assigned to Cu(II) to Cu(III) oxidation.

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Structural and Electrochemical Comparison of Copper(II) Complexes with Tripodal Ligands

Cited by 183 publications

References 47 publications

2-Rhodaoxetanes: Their Formation of Oxidation of [RhI(ethene)]+ and Their Reactivity upon Protonation

2-Rhodaoxetanes: Their Formation of Oxidation of [RhI(ethene)]+ and Their Reactivity upon Protonation

Designing a functional type 2 copper center that has nitrite reductase activity within α-helical coiled coils

Synthesis, Structure and Electrochemistry of Tetranuclear Oxygen-Centered Copper(II) Clusters with Acetylacetone and Benz-pyrazole Hydrolyzed Derivatives as Ligand

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