Spin densities in hydrocarbon ions with degenerate ground states

Hobey, William D.

doi:10.1080/00268976300101101

Cited by 13 publications

(4 citation statements)

References 13 publications

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“…Benzene-1 ,3, S-d a was prepared from aniline by the procedure of Best and Wilson.1 9 No other isotopic species were detected in the sample, indicating an isotopic purity of at least 98% as estimated from the weakest lines of the deuteriobenzenes with lower degrees of deuteration which could have been observed. Materials Benzene-l-d was prepared by treating phenyl Grignard with D 2 0; the sample prepared in this way contained approximatelyl7 4% of C 6 H 6 • Benzene-l,4-d 2 and benzene-2,6-d 2 were the gift of G. W. Robinson of the California Institute of Technology.Is The benzene-1 ,4-d 2 sample exhibited lines arising from about a 3% impurity of benzene-i-d, while the benzene-2,6-d 2 exhibited no extra lines, indicating an isotopic purity17 of at least 96%.…”

Section: Methodsmentioning

confidence: 98%

Effects of Deuterium Substitution on the ESR Spectrum of the Benzene Negative Ion

Lawler

Fraenkel

1968

The Journal of Chemical Physics

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An investigation has been made of the effects of deuterium substitution on the electron spin resonance spectrum of the benzene negative ion. Spectra of the benzene-1-d, benzene-I, 3-d 2 , benzene-I, 4-~, benzene-1,3,5-d3, and benzene-d6 anion radicals have been obtained at -100° and -120°C, and a more extensive study of the temperature dependence of the spectrum of the benzene-I, 4-d2 anion has also been carried out. The results for the benzene-1,3-d2 and benzene-1,4-d2 anions are in agreement with those reported previously for the benzene-1-d anion: The degeneracy of the benzene negative ion is removed by deuterium substitution. As expected, the degeneracy is not lifted in the benzene-I, 3, 5-d s and benzene-ds anions which have threefold or higher symmetry. The temperature dependence of the hyperfine splittings in those radicals which do not possess threefold or higher symmetry was found to be different from that of the unsubstituted benzene anion, and when compared to the benzene anion, some hyperfine splittings increase with temperature while others decrease. In addition, the proton--deuteron splitting-constant ratio was found to be approximately (aR/a D ) =6.18 in all of the radicals studied instead of the value (aR/a D ) =6.514 expected solely on the basis of the magnetic properties of the two isotopes. The effects of deuterium substitution are analyzed by assuming a rapid thermal equilibration between states corresponding to the symmetric and antisymmetric orbitals of the radicals, and estimates are made from the experimental data of the energy separations and relative populations of the two states. These depend on theoretical values for the spin densities; with a Huckel molecular orbital calculation they are -20, 22, and -38 cm-1 , respectively, for the benzene-1-d, benzene-1,3-d2, benzene-1,4-d2 anions. The spin densities and energy separations of the symmetric and antisymmetric forms have been calculated using the Huckel MO method without including vibronic interactions by using both a Coulomb and resonance-integral perturbation for the effects of deuterium substitution.

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Section: Methodsmentioning

confidence: 98%

Effects of Deuterium Substitution on the ESR Spectrum of the Benzene Negative Ion

Lawler

Fraenkel

1968

The Journal of Chemical Physics

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“…We follow Hobey [8] in using the method of Pariser and Parr [9] to determine the values of Hz and (Ez-Eo) for the relevant states by expanding them in terms of integrals involving the atomic orbitals. The one-electron part of the Hamihonian (h) leads to integrals of the type:…”

Section: Configuration Interactionmentioning

confidence: 99%

“…Eight internal symmetry coordinates, Sj, may be defined by: 8 Sj=(1/~/S)~yS(n 1)tn, j=0,_+l, +2, +3,4;…”

Section: =Oafxa(x)'xa(x)dx+o'fx(x)*(x)dn (23)mentioning

confidence: 99%

“…The effect of this configuration interaction on the electron spin densities at the carbon atoms is estimated by a first-order perturbation method similar to that of Hobey [8]. The procedure is simplified by the use of orthonormal complex molecular orbitals: It is convenient to consider the linear combinations: ReA = ( --i/~/2)(Re+ --Re_) and } (9) ReB = (1/V/2)(Re+ + Re_), which correspond to the molecular orbitals CA and CB defined in (1) and have spin density distributions given by equations (3) and (2) respectively.…”

Section: Configuration Interactionmentioning

confidence: 99%

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Vibronic effects on electron resonance spectra: the alkyl cyclooctatetraene anions

Moss¹

1966

Molecular Physics

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Computation of the ESR. Coupling Constants of the [16]Annulene Radical Anion; Theoretical and Experimental Reinvestigation of the Excited States of [16]Annulene and its Mono‐ and Dinegative Ions

Baumann

Oth

1980

Helvetica Chimica Acta

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SummaryThe problem of assigning the two small ESR. coupling constants of the [lblannulene radical anion to the two sets of four equivalent outer and inner ring protons is treated by three different semiempirical MO methods. All three methods indicate that the smaller coupling constant (0.743 Gauss) should be assigned to the inner protons, and the larger one (0.963 Gauss) to the outer ones. The electronic spectra of [ 16]annulene, its radical anion, and its dianion have been remeasured. Especially interesting was the detection of a symmetry-forbidden band of the radical anion at 1473 nm (6789 cm-', logc 2.57). The spectra are discussed in terms of different MO models.

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Spin densities in hydrocarbon ions with degenerate ground states

Cited by 13 publications

References 13 publications

Effects of Deuterium Substitution on the ESR Spectrum of the Benzene Negative Ion

Effects of Deuterium Substitution on the ESR Spectrum of the Benzene Negative Ion

Vibronic effects on electron resonance spectra: the alkyl cyclooctatetraene anions

Computation of the ESR. Coupling Constants of the [16]Annulene Radical Anion; Theoretical and Experimental Reinvestigation of the Excited States of [16]Annulene and its Mono‐ and Dinegative Ions

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