Spin-pairing model of dioxygen binding and its application to various transition-metal systems as well as hemoglobin cooperativity

Drago, Russell S.; Corden, Barry B.

doi:10.1021/ar50154a003

Cited by 104 publications

(35 citation statements)

References 45 publications

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“…This picture is consistent with 0-0 stretching frequencies observed by Raman spectroscopy resembling those in H,O, and Na,O, [22]. An alternate viewpoint which stresses the spinpairing aspect of the 0,-addition reaction has been taken by Drago & Corden [23]. Combining the radicals CO" and 0, will of course lead to a similar orbital description of the binuclear complex, but its equilibrium ground-state geometry is obviously better approximated by assuming donation of an electron pair from 0;-to Co"'.…”

Section: ' )supporting

confidence: 82%

Molecular Structure of the Bis[tris(2‐aminoethyl)aminecyano]dicobalt(III) Ion and its UV/VIS Spectrum

Fallab

Zehnder

1984

Helvetica Chimica Acta

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Sumn2aryFormation of p-peroxodicobalt(lI1) complexes has been studied in solutions containing tris(2-aminoethyl)aminecobalt(II) and additional monodentate ligands X. Oxygenation of Co(I1)-complexes invariably leads to products which strongly absorb in the near UV. Their absorption spectrum is characterized by broad and intense CT bands reaching into the visible and thus giving rise to yellow and brown solution colors [l]. Somewhat conflicting rules relating the number of bands observed between 250 and 450 nm to the structure have been published in [2-41. Etmpirically, three types of spectra can be distinguished (Fig. I ) : i. Most common in singly bridged p-peroxodicobalt(II1) complexes L,CoOOCoL, is a strong band close to 300 nm with a molar extinction E 3 10000M~' cm-'. In addition, a flat shoulder of much lower intensity around 400 nm is frequently observed. ii. In some cases the main absorption band seems split into two peaks of lower but approximately equal intensity with maxima

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Section: ' )supporting

confidence: 82%

Molecular Structure of the Bis[tris(2‐aminoethyl)aminecyano]dicobalt(III) Ion and its UV/VIS Spectrum

Fallab

Zehnder

1984

Helvetica Chimica Acta

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“…. .f :'0: (_I (25) . ( :.1 (26) A similar valence-bond representation pertains for the anion soi, with a sulfur atom replacing the central oxygen atom.…”

Section: -2 Co; Abd Bf2mentioning

confidence: 99%

“…(12) and (13), and the ,* and ,** configurations are obtained from the, configurations by means of the excitations indicated in Eqn. (25).…”

Section: N 2 0mentioning

confidence: 99%

“…One 2-consequence., of this is that the S-S bond-number for S204 must be rather less than unity, and the S-S bond is therefore longer than a single bon~ In (22), the sulphur orbitals that form the S-S a-bond of (19) are both doubly-occupied. As is the case for N204 (Section 7-1), the resulting non-bonded repulsions must contribute to some of the lengthening of the S-S bon~ The A-A bond-lengths for some A 2 Y4 systems, with A" B, Nor P, and y" halogen, are reported in Table 7 (23)- (25). Alternatively, the odd electron for each of the AY 2 monomers (Table 6-1) is not localized entirely in a boron, nitrogen or phosphorus atomic orbital, and on dimerization an incomplete electron-pair bond is formed between pairs of these atoms.…”

mentioning

confidence: 97%

“…If this point of view is adopted, then the valence-bond structure (29) is obtained for the complex in which both NO+ and NO-have coordinated to the low-spin Ru 2 + of (28). It is now possible to generate "increased-valence" structure (25) from (29) :t'!==9: (27) • 4d 55 _ 5 p _ (28) "N~: …”

mentioning

confidence: 99%

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Qualitative Valence-Bond Descriptions of Electron-Rich Molecules: Pauling “3-Electron Bonds” and “Increased-Valence” Theory

Harcourt¹

1982

Lecture Notes in Chemistry

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PREFACEThis book provides qualitative molecular orbital and valence-bond descriptions of the electronic structures for electron-rich molecules, with strong emphasis given to the valence-bond approach. Electron-rich molecules form an extremely large class of molecules, and the results of quantum mechanical studies from different laboratories indicate that qualitative valence-bond descriptions for many of these molecules are incomplete in so far as they usually omit "long-bond" Lewis structures _.0 ••-are equivalent to resonance between standard and "long-bond" Lewis structures, and usually involve Pauling "3-electron bonds" as diatomic components. Because they include both the "long-bond" and the standard Lewis structures, the "increasedvalence" structures must always provide a lower-energy representation of electronic structure than do the more familiar qualitative descriptions that utilize only the standard Lewis structures.To provide the necessary background for readers who are familiar only with the elements of qualitative valence-bond and molecular orbital theory, extensive use is made of an elementary, even pedagogical., approach. Some relevant valence-bond and molecular orbital concepts are reViewed briefly in the first chapter. After a IV discussion of the need for an "increased-valence" theory in Chapter 2, Chapters 3 to 9 are concerned primarily with qualitative descriptions of the electronic structures for numerous paramagnetic molecules that. may have Pauling "3-electron bonds" as components in their valence-bond structures. The bonding and magnetic behaviour for the dimers of some of these molecules are also discussed in Chapters 7 and 8, usingboth Lewis valence-bond and molecular orbital theory. It is shown that if the monomer has a Pauling "3-electron bond" then the dimer may require "long-bond" as well as standard Lewis structures to contribute significantly to the ground-stateresonance. An "increased-valence" description of the bonding for one of these dimers, namely N 2 0 4 , is developed in Chapter 10; this provides a convenient connection between the pauling "3-electron bond" theory for paramagnetic molecules, and the "increased-valence" theory of the remaining Chapters for (mostly) diamagnetic molecules.The "increased-valence" theory represents a natural extension of the more familiar LewiS-Langmuir-pauling valence-bond theory, and therefore an understanding of it may be useful for all chemists who have an interest in simple descriptions of electronic structure. For more than a decade, I have published various papers on this subject, and the present volume includes a considerable number of examples from them, together with numerous new applications.For readers who wish to give primary consideration to the "increased-valence" theory, Sections 3-6, 3-9, 4-1 to 4-7, 6-1, 7-1 and 7-2 are the main components of the earlier chapters that are required as background for Chapters 10 to 24. A reading of Chapter 2 might also be appropriate in order to obtain a rationalization of the need for an "increas...

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Binding and Activation of Molecular Oxygen by Copper Complexes

Karlin

Gultneh

1987

Progress in Inorganic Chemistry

215

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Spin-pairing model of dioxygen binding and its application to various transition-metal systems as well as hemoglobin cooperativity

Cited by 104 publications

References 45 publications

Molecular Structure of the Bis[tris(2‐aminoethyl)aminecyano]dicobalt(III) Ion and its UV/VIS Spectrum

Molecular Structure of the Bis[tris(2‐aminoethyl)aminecyano]dicobalt(III) Ion and its UV/VIS Spectrum

Qualitative Valence-Bond Descriptions of Electron-Rich Molecules: Pauling “3-Electron Bonds” and “Increased-Valence” Theory

Binding and Activation of Molecular Oxygen by Copper Complexes

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