The Cupric Ion in a Trigonal Crystalline Electric Field

Bleaney, B.; Bowers, K D

doi:10.1088/0370-1298/65/8/111

Cited by 386 publications

(397 citation statements)

References 5 publications

Supporting

Mentioning

373

Contrasting

Unclassified

Order By: Relevance

“…They coincide, as obvious, with the well known data of the undoped copper acetate complex [9,10]. A specific discussion of these will, therefore, not be repeated here.…”

Section: Resultssupporting

confidence: 80%

“…Within the errors, the tensors g, D, and A'Cu have coincident axes. These, as known [9], are parallel to the salient molecular directions with the maximum values (z axis) along the copper-copper direction and the V ' axis lying in the crystallographic ac-plane. This information can be utilized to deduce the orienta tion of the three mutually orthogonal planes with respect to the unit cell without a preliminary orientation of the crystal.…”

Section: Resultsmentioning

confidence: 96%

See 1 more Smart Citation

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni²⁺ — Cu²⁺ Exchange-Coupled Pairs

Buluggiu

1984

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

Electron paramagnetic resonance measurements on nickel(II) doped copper(II) acetate monohydrate single crystals have been made. In the liquid helium temperature range, spectra have been observed which may be assigned to Ni2+-C u2+ strongly coupled mixed pairs in the state of total spin S= 1/2. This result represents a definite difference of magnetic behaviour from the case of the nickel(II) doped dicopper(II) tetra(J u-benzoato-0.0')bis(quinoline) complex, which has the same sandwich dimeric structure but shows spectra indicative of a S=3/2 state. Apart from this difference, unusual EPR data are found such as pronounced misalignments of g with respect to the relevant pair axes and very large values of the hyperfine coupling constant of the copper nucleus, which characteristically recall that case.

show abstract

“…They coincide, as obvious, with the well known data of the undoped copper acetate complex [9,10]. A specific discussion of these will, therefore, not be repeated here.…”

Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 96%

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni²⁺ — Cu²⁺ Exchange-Coupled Pairs

Buluggiu

1984

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

show abstract

“…35 The two copper ions interact, with an exchange interaction H = -2JS 1 S 2 . In this isotropic Heisenberg Hamiltonian, a negative value of J refers to an antiferromagnetic interaction within the dimer, while a positive J refers to a ferromagnetic one.…”

Section: Magnetic Propertiesmentioning

confidence: 99%

Equilibria and catalytic properties of a chloro-bridged Diimine copper(II) complex in the N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) oxidation

Alves¹,

Almeida-Filho²,

Santos³

et al. 2004

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

2 Cl 2 ]X 2 ·nH 2 O preparada como sais perclorato 3, nitrato 4 e cloreto 5, respectivamente, foram isoladas e caracterizadas por técnicas espectroscópicas (UV/Vis, IV e EPR). O composto 2 teve sua estrutura determinada por cristalografia de raios-X. Em solventes não-aquosos predomina a espécie dinuclear, enquanto em solução aquosa, ou solventes contendo água, um equilíbrio entre a espécie dinuclear e a mononuclear 1 foi observado. Estudos cinéticos, em metanol, da oxidação catalisada de TMPD indicaram uma dependência de primeira-ordem da velocidade inicial com a concentração de catalisador e um efeito de saturação com aumento da concentração de substrato. O composto dinuclear é mais reativo que o mono-, e experimentos adicionais mostraram que o contra-íon cloreto afeta significativamente os parâmetros cinéticos, deslocando o equilíbrio envolvendo as espécies 2 e 5, além de estabilizar um par iônico com o substrato.Some new copper(II) complexes with a tridentate imine ligand, bimpy (or 2-(benzimidazolyl)methylene-2-amino-1-ethylpyridine), were prepared, and had their catalytic activity in the N,N,N´,N´-tetramethyl-p-phenylenediamine (TMPD) oxidation compared. Mononuclear species, [Cu(bimpy)(H 2 O) 2 ](NO 3 ) 2 , (1) and [Cu(bimpy)Cl 2 ]·H 2 O, (2), as well as the dinuclear species containing chloro-bridges, [Cu 2 (bimpy) 2 Cl 2 ]X 2 ·nH 2 O as perchlorate 3, nitrate 4 and chloride 5 salts, respectively, were obtained and characterized by different techniques (UV/Vis, IR, EPR and X-ray crystallography). In non-aqueous solvents, the dinuclear species predominates; however, in aqueous solution or solvents containing water, equilibrium between dinuclear and correlated mononuclear species 1 was verified. Kinetic studies, in methanol solution, on the catalyzed TMPD oxidation indicated a first-order dependence of the initial rate with the catalyst concentration, and a saturation effect with increasing concentrations of the substrate. The dinuclear species was observed to be more reactive than the mononuclear one, and further experiments showed that the counter-ion chloride can significantly affect the kinetic parameters, mostly by shifting the mono-/dinuclear equilibrium, and stabilizing an ion-pair with the substrate.Keywords: copper(II) complexes, dinuclear species, equilibria, kinetics, catalytic activity IntroductionCopper complexes containing diimines have been extensively studied, and reported as good models for a variety of enzymes associated to the molecular oxygen metabolism. 1 Additionally some of them were used to construct exotic molecular architectures, sensitize photoelectrochemical cells, label biomaterials as the basis for selective sensors, and also to obtain new magnetic materials. 2 Copper-containing active sites are responsible, in vivo, for the catalyzed oxidation of phenols, and amines, where two-electron transfer occurs between the substrate and two metal centres, as in tyrosinase and catechol oxidases, 3 or 873 Equilibria and Catalytic Properties of a Chloro-Bridged Diimine Copper(II) Complex V...

show abstract

“…The temperature dependence of the magnetic susceptibility of such systems is distinctive and may be used to distinguish antiferromagnetic coupling from a truly diamagnetic structure-e.g., a Cu(I) dimer. For two antiferromagnetically coupled S = 1/2 Cu(II) ions, the susceptibility will be a maximum at a temperature that is simply related to the energy difference, J, between the diamagnetic ground state and the paramagnetic excited state (7). Antiferromagnetic coupling between two copper ions has been observed in a wide variety of dimeric Cu(II) complexes (8) and in the four-copper derivative of bovine superoxide dismutase (9).…”

mentioning

confidence: 99%

Magnetic susceptibility studies of laccase and oxyhemocyanin.

Dooley¹,

Scott²,

Ellinghaus³

et al. 1978

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

View full text Add to dashboard Cite

(1,2), and the oxidases laccase, ascorbate oxidase, and ceruloplasmin (3). Additionally cytochrome c oxidase has been proposed to contain a coupled heme ironcopper pair as the site of dioxygen binding and reduction (4). In no case has any electron paramagnetic resonance (EPR) signal attributable to a binuclear site been observed in the native protein (5). Although other structural possibilities are consistent with this observation, it is generally thought that the metal ions involved are strongly antiferromagnetically coupled, resulting in a diamagnetic or even spin ground state (5, 6). The temperature dependence of the magnetic susceptibility of such systems is distinctive and may be used to distinguish antiferromagnetic coupling from a truly diamagnetic structure-e.g., a Cu(I) dimer. For two antiferromagnetically coupled S = 1/2 Cu(II) ions, the susceptibility will be a maximum at a temperature that is simply related to the energy difference, J, between the diamagnetic ground state and the paramagnetic excited state (7). Antiferromagnetic coupling between two copper ions has been observed in a wide variety of dimeric Cu(II) complexes (8) and in the four-copper derivative of bovine superoxide dismutase (9). We have focused our efforts on oxyhemocyanin and laccase. It is generally accepted that the dioxygen binding site in oxyhemocyanin is a binuclear copper(II) peroxo complex, the evidence coming mainly from resonance Raman (10) and other spectroscopic (11,12) experiments. The four copper atoms in laccase are distributed in types 1 (paramagnetic), 2 (paramagnetic), and 3 (binuclear; EPR nondetectable) sites. The type 3 coppers apparently function as a two-electron acceptor and are thought to be the site of interaction with dioxygen (3).Previous magnetic susceptibility measurements showed oxyhemocyanin to be diamagnetic over the temperature range 35-250 K (13,14). Over this same range, the susceptibility of Rhus laccase showed, in addition to the Curie law paramagnetism of copper types 1 and 2, non-Curie paramagnetism at temperatures above 80 K that was consistent with an antiferromagnetically coupled Cu(II) pair with J = 170 ± 30 cm1 (13).Owing to the fact that the fit of theory to the observed deviation from Curie law in laccase was not entirely satisfactory (due in part to the low precision of the measurements) and realizing the importance of these observations to understanding the copper-site electronic structure of hemocyanin and laccase, we have remeasured the susceptibilities over a wider temperature range by using susceptometers recently developed at SHE Corporation, San Diego, CA. Although oxyhemocyanin was again observed to be essentially diamagnetic over the entire temperature range, laccase, in contrast to our previous results, displayed only the Curie law behavior of copper types 1 and 2 over the temperature range examined. MATERIALS AND METHODSRhus vernidfera laccase was purified by the method of Reinhammar (15) from the acetone powder (Saito & Co., Ltd., Japan) to a A2o/A614 value <15. A sample w...

show abstract

The Cupric Ion in a Trigonal Crystalline Electric Field

Cited by 386 publications

References 5 publications

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni²⁺ — Cu²⁺ Exchange-Coupled Pairs

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni²⁺ — Cu²⁺ Exchange-Coupled Pairs

Equilibria and catalytic properties of a chloro-bridged Diimine copper(II) complex in the N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) oxidation

Magnetic susceptibility studies of laccase and oxyhemocyanin.

Contact Info

Product

Resources

About

The Cupric Ion in a Trigonal Crystalline Electric Field

Cited by 386 publications

References 5 publications

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni2+ — Cu2+ Exchange-Coupled Pairs

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni2+ — Cu2+ Exchange-Coupled Pairs

Equilibria and catalytic properties of a chloro-bridged Diimine copper(II) complex in the N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) oxidation

Magnetic susceptibility studies of laccase and oxyhemocyanin.

Contact Info

Product

Resources

About

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni²⁺ — Cu²⁺ Exchange-Coupled Pairs

EPR Data on Ni(II) Doped Cu(II) Acetate Monohydrate Single Crystals: Evidence of Ni²⁺ — Cu²⁺ Exchange-Coupled Pairs