Theoretical Calculations on Ions and Radicals. I. A Restricted Hartree—Fock Perturbation Method for the Calculation of Spin Densities

Bloor, J. E.; Gilson, Bruce R.; Daykin, P. N.

doi:10.1021/j100877a019

Cited by 15 publications

(5 citation statements)

References 10 publications

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“…The SCFMO method has been shown to predict successfully at least the first two electronic transitions of many polycyclic hydro-carbons3'15•17,18 as well as the spin densities of the corresponding negative ions. 5 For the cyano compound of Figure 1, we have calculated by the standard SCFMO + Cl3•15 method the first two transition energies and compared them with the experimental data when available. The data are summarized in Table V and expressed graphically for set 1 calculations in Figure 3.…”

Section: Table Vi: Comparison Of Polarographic Reductionmentioning

confidence: 99%

Theoretical calculations on ions and radicals. II. SCFMO [self-consistent field molecular orbital] calculations on the excited states of aromatic nitriles and the spin density distributions of the corresponding anions

Bloor¹,

Gilson²,

Shillady³

1967

J. Phys. Chem.

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Section: Table Vi: Comparison Of Polarographic Reductionmentioning

confidence: 99%

Theoretical calculations on ions and radicals. II. SCFMO [self-consistent field molecular orbital] calculations on the excited states of aromatic nitriles and the spin density distributions of the corresponding anions

Bloor¹,

Gilson²,

Shillady³

1967

J. Phys. Chem.

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“…Interestingly, a consideration of the screening effect of other electrons in the molecule will have a similar effect of reducing the theoretical value of such integrals [29]. Now, assuming the correction for the integral to be zero at a distance R = 1.397 x 2 A we obtain the following expression for (ii Ijj) as a function of distance R(in A) (5) (ii Ijj) = 11.77 -3.6596R + 0.4255R2 eV For distances lower than 2.794 A Equation (5) was used, while for higher distances (ii 1 j j ) ' s were directly calculated.…”

Section: ~( 2 P )mentioning

confidence: 99%

“…The simple McConnell relationship [ 11, together with the result of molecular orbital (MO) theories such as HMO [2,31 McLachlan approximate SCF [2, 41, restricted Hartree-Fock (RHF) [5,61 and Unrestricted Hartree-Fock (UHF) [S, 71, has been used extensively for the interpretation of isotropic proton hyperfine splittings in the e.s.r. spectra of ii--electron radicals.…”

Section: Introductionmentioning

confidence: 99%

Unrestricted Hartree‐Fock calculations of spin densities with orthogonalized atomic orbitals: Proton and ¹³C hyperfine splittings in some pi hydrocarbon radicals

Nanda

Narasimhan

1972

Int J of Quantum Chemistry

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AbstractsThe spin density distribution in a few hydrocarbon radicals has been calculated using orthogonalized atomic orbitals in the Unrestricted Hartree-Fock formalism of Amos and Snyder and including certain more important two-electron hybrid and exchange integrals and all the core-resonance integrals. Our calculated spin densities for the cation and anion radicals of alternant hydrocarbons, which are now different due to the breakdown of the pairing theorem, are, in general, of the right relative order so that even the simple McConnell type of relation can account partly for the observed differences in the proton splittings between cations and anions. The proton splittings for position 2 of naphthalene and anthracene radical ions are correctly predicted, thus clearing up the well-known cation-anion anomaly for this position. Comparative calculations have been made to show that the spin density results are worsened with the neglect of the integrals of the type mentioned before. An empirical analysis correlating the observed 13C splittings and the spin density results over a non-orthogonal basis set shows that the available 13C splittings in alternant hydrocarbon radical ions can be explained with a set of sigma-pi parameters which are consistent with the theory. It is shown that even though the spin densities in cations and anions may be different, these can lead to similar 13C splittings.La distribution de la densitt de spin dans quelques radicaux d'hydrocarbures a t t t calculte avec des orbitales atomiques orthogonaliskes dans le formalisme de Hartree-Fock sans restrictions de Amos et Snyder; certaines inttgrales importantes d'hybride et d'tchange et toutes les inttgrales de rtsonance de coeur ont t t t inches. Nos densitts de spin pour les cations et les anions des radicaux des hydrocarbures alternants, qui sont maintenant difftrentes, parce que le "thtortme des paires" n'est plus valable, sont en gtnkral dans I'ordre relatif correct. En constquent meme la relation simple de McConnell peut rendre compte partiellement des differences observtes dans les dtcompositions protoniques entre les cations et les anions. Ces dtcompositions sont prtdites correctement pour la position 2 des ions du n a p h t a h e et de I'anthractne ce qui clarifie l'anomalie bien connue de cette position-la.Des calculs comparatifs ont t t t faits pour montrer que les densitts de spin deviennent pires, si l'on neglige les inttgrales mentionntes. Une analyse empirique, corrtlant les dtcompositions observtes de 13C et les densitts de spin obtenues d'une base non-orthogonale, montre que les dtcompositions connues de 13C dans les ions des radicaux des hydrocarbures alternants peuvent &tre expliqutes avec un nombre de paramttres sigmapi, qui sont conformes A la thtorie. I1 est demontrt que m&me si les densitts de spin peuvent Die Spindichteverteilung in einigen Kohlenwasserstoffradikalen ist mit orthogonalisierten Atomorbitalen im Rahmen der uneingeschrankten Hartree-Fock-Formalismus von Amos und Snyder berechnet worden, wobei gewisse wicht...

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“…In figure 5 the (experimental) alt versus the (theoretical) aH plot is given for the Htickel method. Bloor et al [22] have shown that for aromatic ions no significant improvement could be obtained by adding extra terms to the McConnell equation to take into account excess charge [23,24] or bond-order effects [22]. As the electron distribution in N-heterocyclic aromatics is not as homogeneous as in aromatic hydrocarbons, an extension of the McConnell equation, taking into account the excess charge, was tested [23].…”

Section: The Reliability Of Mcconnell' S Equation In the Diazanaphthamentioning

confidence: 99%

The McConnell equation for E.S.R. spectra of symmetrical diazanaphthalenes

1971

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Electron spin resonance spectra of the six symmetrical diazanaphthalene anions in N,N-dimethylformamide have been measured. The anions were generated within the microwave cavity by electro-reduction of the parent compound. The McConnell equation all= 0CC H pc has been tested for the diazanaphthalenes with pc values calculated by the Hiickel method and by the Pariser-Parr-Pople S.C.F. method with variable resonance integrals.

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Theoretical Calculations on Ions and Radicals. I. A Restricted Hartree—Fock Perturbation Method for the Calculation of Spin Densities

Cited by 15 publications

References 10 publications

Theoretical calculations on ions and radicals. II. SCFMO [self-consistent field molecular orbital] calculations on the excited states of aromatic nitriles and the spin density distributions of the corresponding anions

Theoretical calculations on ions and radicals. II. SCFMO [self-consistent field molecular orbital] calculations on the excited states of aromatic nitriles and the spin density distributions of the corresponding anions

Unrestricted Hartree‐Fock calculations of spin densities with orthogonalized atomic orbitals: Proton and ¹³C hyperfine splittings in some pi hydrocarbon radicals

The McConnell equation for E.S.R. spectra of symmetrical diazanaphthalenes

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Theoretical Calculations on Ions and Radicals. I. A Restricted Hartree—Fock Perturbation Method for the Calculation of Spin Densities

Cited by 15 publications

References 10 publications

Theoretical calculations on ions and radicals. II. SCFMO [self-consistent field molecular orbital] calculations on the excited states of aromatic nitriles and the spin density distributions of the corresponding anions

Theoretical calculations on ions and radicals. II. SCFMO [self-consistent field molecular orbital] calculations on the excited states of aromatic nitriles and the spin density distributions of the corresponding anions

Unrestricted Hartree‐Fock calculations of spin densities with orthogonalized atomic orbitals: Proton and 13C hyperfine splittings in some pi hydrocarbon radicals

The McConnell equation for E.S.R. spectra of symmetrical diazanaphthalenes

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Unrestricted Hartree‐Fock calculations of spin densities with orthogonalized atomic orbitals: Proton and ¹³C hyperfine splittings in some pi hydrocarbon radicals