Hemocyanin models: synthesis, structure, and magnetic properties of a binucleating copper(II) system

A series of copper (II) ), have been synthesized and fully characterized. The substitution reaction of 1 with thiourea was studied under pseudofirst-order conditions as a function of concentration, temperature and pressure in methanol and acetonitrile as solvents. Two reaction steps that both depended on the nucleophile concentration were observed for both solvents. Substitution of coordinated methanol is about 40 times faster than the substitution of chloride. In acetonitrile, the rate constant for the displacement of coordinated acetonitrile was more than 20 times faster than the substitution of chloride. The reported activation parameters indicate that both reaction steps follow a dissociative mechanism in both solvents. On going from methanol to acetonitrile, the rate constant for the displacement of the solvent becomes more than 200 times faster due to the more labile acetonitrile, but the substitution mechanism remained to have a dissociative character. The antioxidant activities of 1-4 were evaluated for superoxide dismutase (SOD), glutathione-stransferase (GST0 and glutathione reduced (GSH-Rd) activity. 1 and 2 were found to show ( p < 0.05) the highest antioxidant activity in comparison to 3 and 4, which can be ascribed to the geometric configuration as well as the nature of the co-ligand. 1 showed catechol oxidase activity with turnover numbers of 20 min −1 and a coordination affinity for 3,5-DTBC of K 1 , = 31 mM −1 . K 1 is rather large and seems to be typical for faster biomimetic models, and also for the enzyme itself (25 mM −1). The reaction rate depended linearly on the complex concentration, indicating a first-order dependence on the catalyst concentration.

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“…at high [3,. At a V/[Cu II complex] value of k 2 /2, the [3,5-DTBC] = 1/K 1 , which according to Fig.…”

Section: Catechol Oxidase Mimetic Activitymentioning

confidence: 73%

Spectroscopic, thermodynamic, kinetic studies and oxidase/antioxidant biomimetic catalytic activities of tris(3,5-dimethylpyrazolyl)borate Cu(ii) complexes

et al. 2015

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“…These results allow one to draw the following conclusions: i) Regardless of the coordination number of the metals, all the pathways involving only one carbonate ligand (J 1 , J 2 , J 3 ) lead to similar J values of strength seemingly correlated to the average Co-O-C angles; ii) despite being mediated by two CO 3 2À bridges, the coupling J 4 is weaker than these above, presumably because it occurs through longer Co À O bonds and narrower Co-O-C angles (on average); iii) the pathways leading to J 5 , J 6 , and J 7 are one syn,syn-CO 3 2À and one phenoxo-like bridge. This combination is expected to lead to a ligand counter-complementarity effect on the coupling strength, [40,41] by which, the interaction of each type of ligand with the metallic magnetic orbitals causes a decrease of the energy gaps between SOMOs, thereby diminishing the strength of the antiferromagnetic (AF) coupling. As observed before, [40,41] this also causes a shift towards larger values of the M-O-M angle at which the interaction switches from ferromagnetic (F) to AF in phenoxo-bridged systems (q SWITCH ).…”

Section: Full Papermentioning

confidence: 99%

“…This combination is expected to lead to a ligand counter-complementarity effect on the coupling strength, [40,41] by which, the interaction of each type of ligand with the metallic magnetic orbitals causes a decrease of the energy gaps between SOMOs, thereby diminishing the strength of the antiferromagnetic (AF) coupling. As observed before, [40,41] this also causes a shift towards larger values of the M-O-M angle at which the interaction switches from ferromagnetic (F) to AF in phenoxo-bridged systems (q SWITCH ). The calculations on 1 indicate that this switch occurs now towards 1098; iv) for the case of J 8 , the metals exhibit two monoatomic m-O bridges, thus precluding the effect of counter-complementarity.…”

Section: Full Papermentioning

confidence: 99%

Double‐CO₃²⁻ Centered [Co^II₅] Wheel and Modeling of Its Magnetic Properties

Sarkar

Aromı́

Cano

et al. 2010

Chemistry A European J

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A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S=3/2 ions (CN=5) with ions exhibiting strong spin-orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2-300 K) yielding parameters of g and D (for the five-coordinate Co(II) ions), of A, κ, λ, and Δ (for the metals with spin-orbit coupling) and of the exchange constants J. The agreement with results from DFT calculations, also presented here, is remarkable.

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“…The CuϪN distances are, however, considerably shorter (∆ ϭ 0.05Ϫ0.15 Å ) relative to the structurally similar tri-or tetrasubstituted (benz)imidazole derivatives of 1,3-diamino-2-propanol. [21] This is probably due to the less distorted tetragonal plane in 2. On the other hand, the CuϪO distances are typical as compared with the related dinuclear complexes.…”

Section: B [Cu 2 (Bimido ؊1h )(Dpp)(clo 4 )(Ch 3 Oh)]clo 4 ⋅1/2h 2 Omentioning

confidence: 99%

Structure, Equilibrium and Ribonuclease Activity of Copper(II) and Zinc(II) Complexes Formed with a Dinucleating Bis-Imidazole Ligand

Gajda

Krämer

Jancsó

2000

Eur. J. Inorg. Chem.

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Hemocyanin models: synthesis, structure, and magnetic properties of a binucleating copper(II) system

Cited by 284 publications

References 5 publications

Spectroscopic, thermodynamic, kinetic studies and oxidase/antioxidant biomimetic catalytic activities of tris(3,5-dimethylpyrazolyl)borate Cu(ii) complexes

Spectroscopic, thermodynamic, kinetic studies and oxidase/antioxidant biomimetic catalytic activities of tris(3,5-dimethylpyrazolyl)borate Cu(ii) complexes

Double‐CO₃²⁻ Centered [Co^II₅] Wheel and Modeling of Its Magnetic Properties

Structure, Equilibrium and Ribonuclease Activity of Copper(II) and Zinc(II) Complexes Formed with a Dinucleating Bis-Imidazole Ligand

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Hemocyanin models: synthesis, structure, and magnetic properties of a binucleating copper(II) system

Cited by 284 publications

References 5 publications

Spectroscopic, thermodynamic, kinetic studies and oxidase/antioxidant biomimetic catalytic activities of tris(3,5-dimethylpyrazolyl)borate Cu(ii) complexes

Spectroscopic, thermodynamic, kinetic studies and oxidase/antioxidant biomimetic catalytic activities of tris(3,5-dimethylpyrazolyl)borate Cu(ii) complexes

Double‐CO32− Centered [CoII5] Wheel and Modeling of Its Magnetic Properties

Structure, Equilibrium and Ribonuclease Activity of Copper(II) and Zinc(II) Complexes Formed with a Dinucleating Bis-Imidazole Ligand

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Double‐CO₃²⁻ Centered [Co^II₅] Wheel and Modeling of Its Magnetic Properties