Metal isotope effect on metal-ligand vibrations—XII

Cornilsen, Bahne C.; Nakamoto, Kazuo

doi:10.1016/0022-1902(74)80455-0

Cited by 98 publications

(32 citation statements)

References 17 publications

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“…The presence of three polarized Cu-N (41)(42)(43)(44) stretches is consistent with a molecular symmetry lower than C3V, as found in the x-ray structure of Sa. The polarized emission at 274 cm-' is tentatively assigned to PcU S (41)(42)(43)(44) brations in the proteins are by no means indubitable. The availability of a simple synthetic facsimile system, readily amenable to chemical modification, should now greatly aid in understanding the resonance Raman spectra of the proteins.…”

Section: Methodssupporting

confidence: 54%

Blue copper proteins: Synthesis, spectra, and structures of Cu ^I N ₃ (SR) and Cu ^II N ₃ (SR) active site analogues

Thompson

Marks

Ibers

1977

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

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The reaction of Cu(SR) or [Cu(SR)IC1041 derivatives (SR = p-nitrobenzenethiolate or O-ethylcysteinate) with potassium hydrotris(3,5-dimethyl-1-pyrazolyl)borate produces redox pairs of the stoichiometry CuIN3(SR) and CuIIN3(SR). These complexes are well-defined synthetic approximations to the proposed N3S binding sites of blue (type 1) copper electron transfer proteins. The compounds were investigated by a variety of chemical and spectral (optical, resonance Raman, and electron paramagnetic resonance) techniques; the complex K[Cu(hydrotris(3,5 dimethyl-1-pyrazolyl)borateXp-

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Section: Methodssupporting

confidence: 54%

Blue copper proteins: Synthesis, spectra, and structures of Cu ^I N ₃ (SR) and Cu ^II N ₃ (SR) active site analogues

Thompson

Marks

Ibers

1977

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

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“…Interestingly, even when the reaction was carried out with four-to six-fold excess of ligand, the same CuCl,(Haza), compound was the only complex isolated. We were unable to obtain [Cu(Haza),]Cl,, even though such [CuL,]X, compounds are known with imidazoles (26)(27)(28)(29)(30) and pyridines (3 1 ligands are all formally neutral and coordinated to copper via N7. The square planes, roughly perpendicular to the twofold axis, are bridged by chloride ions lying on the same axis, which complete an overall (4 + 2)-coordination about the metal.…”

Section: Resultsmentioning

confidence: 99%

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Poitras¹,

Beauchamp²

1992

Can. J. Chem.

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The light green trans-CuCl2(Haza)2 adduct precipitates immediately from mixtures of CuCl2•2H2O with excess 7-azaindole (Haza) in methanol. Upon standing in azaindole-rich solution, this solid is replaced by a deep green Cu2Cl4(Haza)6 compound, whose crystal structure (orthorbombic, Fdd2, a = 26.558, b = 23.750, c = 12.727 Ǻ, Z = 8, R = 0.068, Rw = 0.066) shows the presence of square-planar [Cu(Haza)4]2+ and trans-[CuCl2(Haza)2] units connected by bridging Cl− ions, making each Cu atom (4 + 2)-coordinated. Azaindole is bonded to the metal via the pyridine N7 site, whereas the five-membered ring retains its N1—H proton. The azaindole ligands are disordered over two orientations in the [CuCl2(Haza)2] unit. The square-planar Cu species and apical Cl− ions lie on a twofold axis and define along c an infinite chain based on the [Formula: see text] pattern. Equimolar mixtures of azaindole and CuCl2•2H2O yield a brown Cu4OCl6(Haza)4 compound. The crystal structure of its ethyl acetate solvate (monoclinic, P21/c, a = 11.661, b = 22.415, c = 15.077 Ǻ, β = 109.85°, Z = 4, R = 0.048, Rw = 0.054) shows the presence of a tetranuclear cluster consisting of a μ4-oxide ion surrounded by a tetrahedron of Cu(II) atoms bridged in pairs by chlorine atoms. The trigonal-bipyramidal coordination of each copper atom is completed by a monodentate N7-bonded azaindole molecule hydrogen bonded to bridging chlorines via N1—H. The influence of complexation on the infrared spectrum of azaindole is discussed.

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“…It is probable that these, too, represent coupled vibrations in a constrained tetrahedral coordination geometry. In contrast, in the unconstrained tetrahedral dihalobis(imidazole) Zn(II) complexes in which all four ligands appear to have uncoupled vibrations, the normal coordinate analysis gives a best fit by treating the imidazoles as rigid vibrators with a mass of68 atomic mass units (34).…”

Section: Resultsmentioning

confidence: 99%

Normal coordinate analysis of the copper center of azurin and the assignment of its resonance Raman spectrum.

Thamann¹,

Frank²,

Willis³

et al. 1982

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

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Normal coordinate analysis that utilizes a general valence force field and the Wilson FG matrix method has been applied to several structural models representing the active site of the blue copper protein, azurin. The models included tetrahedral and square planar CuN2SS', trigonal CuN2S, and trigonal bipyramidal CuN2SS'O structures in which the Ns are imidazole nitrogens of histidines, S is the thiolate sulfur ofcysteine, S' is the thioether sulfur ofmethionine, and 0 is a peptide carbonyl oxygen. For constant Cu-ligand bond lengths and initial force constants, the force field was refined against the most intense ofthe observed frequencies (424, 404, 369, and 261 cm-) in the resonance Raman spectrum of Pseudomonas aeruginosa azurin. The most satisfactory fit between observed and calculated frequencies occurs for tetrahedral and trigonal structures. The calculations provide detailed assignments for the resonance Raman spectrum of azurin and reveal considerable mixing of Cu-S(Cys) and Cu-N(His) vibrational modes. The trigonal model is favored because it is shown that the =260-cm-vibration is an invariant feature in the resonance Raman spectra ofblue copper proteins, even those lacking a methionine in the vicinity of the copper atom. The present analysis ascribes the high frequencies ofthe Cu-ligand stretching modes and the resonance enhancement to the coupled nature of their vibrations and the Franck-Condon overlaps with predominant (Cys)S--Cu(II) charge transfer bands in the visible region.

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Metal isotope effect on metal-ligand vibrations—XII

Cited by 98 publications

References 17 publications

Blue copper proteins: Synthesis, spectra, and structures of Cu ^I N ₃ (SR) and Cu ^II N ₃ (SR) active site analogues

Blue copper proteins: Synthesis, spectra, and structures of Cu ^I N ₃ (SR) and Cu ^II N ₃ (SR) active site analogues

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Normal coordinate analysis of the copper center of azurin and the assignment of its resonance Raman spectrum.

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Metal isotope effect on metal-ligand vibrations—XII

Cited by 98 publications

References 17 publications

Blue copper proteins: Synthesis, spectra, and structures of Cu I N 3 (SR) and Cu II N 3 (SR) active site analogues

Blue copper proteins: Synthesis, spectra, and structures of Cu I N 3 (SR) and Cu II N 3 (SR) active site analogues

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Normal coordinate analysis of the copper center of azurin and the assignment of its resonance Raman spectrum.

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Product

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About

Blue copper proteins: Synthesis, spectra, and structures of Cu ^I N ₃ (SR) and Cu ^II N ₃ (SR) active site analogues

Blue copper proteins: Synthesis, spectra, and structures of Cu ^I N ₃ (SR) and Cu ^II N ₃ (SR) active site analogues