Near-Infrared Spectra of Some Pseudotetrahedral Complexes of Cobalt (II) and Nickel(II)

Goodgame, D. M. L.; Goodgame, M.

doi:10.1021/ic50024a002

Cited by 82 publications

(27 citation statements)

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“…(12,13), as concluded earlier for cadmium LADH (7). Studies of model compounds (13) suggest that the absorption bands in the 600-to 800-nm range (E > 100 per cobalt atom) reflect tetrahedral coordination geometry consistent with interpretations of absorption maxima (14) previously observed in the near infrared region (7). Fig.…”

supporting

confidence: 82%

Chemical reactivities of catalytic and noncatalytic zinc or cobalt atoms of horse liver alcohol dehydrogenase: differentiation by their thermodynamic and kinetic properties.

Sytkowski¹,

Vallée²

1976

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

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Horse liver alcohol dehydrogenase (EC 1.1.1.1) contains one catalytic and one noncatalytic pair of zinc atoms that can be replaced selectively with cobalt and/ or 65zinc. We have now prepared "hybrid" metalloenzymes by specifically replacing one or both pairs of zinc atoms with Wzinc and/or cobalt. Their differential chemical reactivities serve to characterize the metal atoms at either site. The spectral and kinetic properties of the resultant 65zinc, cobalt, and hybrid enzymes, as well as those of their complexes with 1,10-phenanthroline, identify the metal atoms that are at the catalytic sites and differentiate them from those at the noncatalytic sites. All data are in complete agreement with the results of the x-ray crystal structure analysis. Remarkably, under the conditions used, chemical reactivity, as gauged by thermodynamic methods under equilibrium conditions, identifies the catalytic metal atoms as those which are reactive to I,10-phenanthroline, while this reagent does not affect the noncatalytic pair. Under dynamic conditions the kinetics of the metal-metal exchange reveals the converse to be true: the chemical reactivity of the noncatalytic atoms is much higher and, hence, they exchange more rapidly. The results are examined in terms of thermodynamic and kinetic properties of metal complex ions which serve as the basis of possible mechanisms underlying these observations. Chemical modifications of particular amino-acid side chains affect the activities of enzymes, linking their chemical to their catalytic properties and differentiating functional from other residues. Such differentiation may be the result of thermodynamic, kinetic, or both these features of the reactants. In this context, the characteristic properties of the metals of metalloenzymes enable their use as spectral, kinetic, and spectrokinetic probes (1). The realization that many enzymes may contain different classes of metal atoms allows an extension of these approaches to the delineation of different chemical reactivities of metals in terms of spectra or rates of metal-metal exchange, the interaction of metals with ligands, the environment of metals, and their modes of interaction with substrates or inhibitors.One such enzyme, horse liver alcohol dehydrogenase, LADH, (EC 1.1.1.1) contains four zinc atoms (2, 3) two of which are "catalytic" and two of which are "noncatalytic" or structural, as judged by kinetic, spectroscopic, and chemical evidence (3-5). On this basis, we have designated these Abbreviations: [(LADH)Zn2Zn2], native horse liver alcohol dehydrogenase; OP, 1,10-phenanthroline. In order to differentiate and clarify presentation, the first pair of metal (Me) atoms in the standard formulation is designated the "N" (noncatalytic) and the second the "C" (catalytic) pair, i.e., l(LADH)N2C2I. Hence two classes of zinc as "C" and "N," respectively, and will refer to them in this manner throughout this report. X-ray crystal structure analysis reveals the details of the ligands binding to these pairs of zinc atoms: those ...

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confidence: 82%

Chemical reactivities of catalytic and noncatalytic zinc or cobalt atoms of horse liver alcohol dehydrogenase: differentiation by their thermodynamic and kinetic properties.

Sytkowski¹,

Vallée²

1976

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

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“…The second band is located in the NIR region and it was assigned to the medium energy ν 2 transition. In perfect T d symmetry, the lowest ν 1 transition for Co(II) is electric dipole forbidden, but in C 3v and C 2v symmetries it becomes allowed [25], and it is expected in the region below 5000 cm −1 . Since the quinoline ligand contributes a fairly strong ligand field, for complexes 1-4 at least a part of the ν 1 band was detected in our measurements.…”

Section: Spectroscopymentioning

confidence: 99%

“…The observed spectra are indicative of a tetrahedral configuration of the Co(II) ion. In an idealized T d symmetry three spin-allowed transitions are expected: ν 1 = 4 A 2 ( 4 F) → 4 T 2 ( 4 F), ν 2 = 4 A 2 ( 4 F) → 4 T 1 ( 4 F) and ν 3 = 4 A 2 ( 4 F) → 4 T 1 ( 4 P) in an increasing order of energy [24][25][26]. The first band, observed in the visible region, refers to the highest ν 3 transition.…”

Section: Spectroscopymentioning

confidence: 99%

Halogen atom effect on the magnetic anisotropy of pseudotetrahedral Co(II) complexes with a quinoline ligand

et al. 2015

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“…The halogenotris(triphenylphosphine)nickel compounds have been synthesized by reaction of zr-allyl-Ni-X with excess P(C6Hs)3 and norbornene in a benzene/diethyl ether solution (Porri, Gallazzi & Vitulli, 1967), although alternative synthetic methods are available (Barnett, 1974). The chlorotris(triphenylphosphine)cobalt compound can be synthesized from COC12.6H20 and P(C6Hs)3 in the presence of a reducing agent (Arresta, Rossi & Sacco, 1969 (Goodgame & Goodgame, 1965;Garton, Henn, Powell & Venanzi, 1963). A green crystal of (I) suitable for a single crystal X-ray study (0.5 x 0.4 × 0.5 mm, cut prism) was obtained from a toluene solution of the product and mounted on a glass fiber with epoxy cement.…”

Section: Coci[p(c6hs)3]3 Andmentioning

confidence: 99%

Structures of [CoCl(C18H15P)3] and [NiCl(C18H15P)3].C7H8

Cassidy¹,

Whitmire²

1991

Acta Crystallogr C

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Near-Infrared Spectra of Some Pseudotetrahedral Complexes of Cobalt (II) and Nickel(II)

Cited by 82 publications

References 1 publication

Chemical reactivities of catalytic and noncatalytic zinc or cobalt atoms of horse liver alcohol dehydrogenase: differentiation by their thermodynamic and kinetic properties.

Chemical reactivities of catalytic and noncatalytic zinc or cobalt atoms of horse liver alcohol dehydrogenase: differentiation by their thermodynamic and kinetic properties.

Halogen atom effect on the magnetic anisotropy of pseudotetrahedral Co(II) complexes with a quinoline ligand

Structures of [CoCl(C18H15P)3] and [NiCl(C18H15P)3].C7H8

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