An E.S.R. study of the mono and dinegative ions of triphenylene. Evidence for the Jahn-Teller instability of the triplet dianion

Willigen, H. van; Broekhoven, J. A. M. van; Boer, E. de

doi:10.1080/00268976700100711

Cited by 42 publications

(16 citation statements)

References 34 publications

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“…A triplet ground state has been confirmed experimentally for some symmetrydegenerate molecules 12-41. Topologically degenerate molecules may have lower symmetry. For alternant aromatic hydrocarbons the H M O approximation provides a simple relation for determining the topological degeneracy 1x1: according to this, the hydrocarbon ( I ) has two non-bonding HMOs which are occupied (4) by only two electrons in the ground state. Thus a triplet ground state is to be expected for (1) We attempted to produce the monomeric compound (1) by polarographic reduction of (3) at a rotating platinum electrode.…”

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confidence: 99%

Schlenk's Biradical. – A Molecule in the Triplet Ground State

Kothe

Denkel

Sümmermann

1970

Angew. Chem. Int. Ed. Engl.

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parameters was carried out by the method of least squares with anisotropic temperature factors. After the final cycle including all observed F(hkl) the factor R had a value 0.10. X-ray crystallographic investigation showed, that the previously unobserved structure of a dicubane is in fact present. The cubes are distorted. All the Zn-0-Zn angles are smaller than 90° (81 "-86 ") and all the 0-Zn-0 angles are greater than 90 ' (93 "-98 "). The four atoms centered on the cube faces lie in one plane.

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confidence: 99%

Schlenk's Biradical. – A Molecule in the Triplet Ground State

Kothe

Denkel

Sümmermann

1970

Angew. Chem. Int. Ed. Engl.

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“…A summary of the results is given in the table. The zero-field parameter D in Tpb= becomes independent of the counter-ion and solvent after addition of excess polyether as has been found previously for Tp = [1]. Tentatively we assign the spectra observed under these conditions to the unperturbed dianions.…”

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confidence: 71%

“…When solutions of Tpb= in MTHF (counter ions K + or Na +) are ' titrated ' with a 0.1 molar solution of polyether (diglyme, triglyme or tetraglyme) in MTHF three distinct triplet spectra appear successively, as has been found previously for Tp = [1]. Figure 1, Graph of the relative concentrations of triplet species I, II and III, derived Figure 1.…”

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confidence: 81%

“…Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. [1] demonstrated that alkali metal counter ions may strongly perturb the spin distribution. Here we report results which prove that similar polarizing effects influence the triplet dianions of 1,3,5-triphenylbenzene (Tpb) and decacyclene (Dec) [2].…”

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confidence: 99%

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Counter-ion effects on the spin density distribution in triplet aromatic dianions

1968

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“…The triphenylene dianion (19), which has a high degree of symmetry and only limited possibilities of distortion, appears as a triplet ground state (39,40) ( Figure 9). The effect of removal of this symmetry on the paratropicity of the system is reflected by the calculated HOMO-LUMO energy gap and its manifestation in the line shape of the *H NMR spectrum.…”

Section: Relationship Of Topology and Structure To Paratropicity Of 4nmentioning

confidence: 99%

NMR Studies of 4n π-Conjugated Polycyclic Anions

Rabinovitz

Cohen

1987

Advances in Chemistry

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The energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) de termines the line shape and chemical shift of 4n π polycyclic doubly charged systems. Narrower energy gaps correspond to more signif icant line broadening in the 1 H NMR bands. This line broadening is attributable to a singlet-triplet equilibrium that depends on the HOMO-LUMO gap. The topology of the system influences the par atropicity of these 4n π polycyclic dianions. Whereas the triphenylene dianion does not exhibit a 1 H NMR spectrum, a gradual change toward a highly resolved spectrum is obtained for the tri -benzo[a,c,i]phenazine dianion. A correlation between the HOMO -LUMO gap and the paratropic shift of these dianions is demonstrated. THE NOTI ON OF AROMATI CI TY is one of the most intriguing problems inorganic chemistry and has drawn the attention of chemists since Kekulé's ingenious proposal (1) in 1872 of the structure of benzene. The concept of antiaromaticity introduced by Breslow (2, 3) about a century later emphasized the perplexity of aromaticity. Nevertheless, numerous physical and chemical properties of many groups of compounds are attributed to their

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An E.S.R. study of the mono and dinegative ions of triphenylene. Evidence for the Jahn-Teller instability of the triplet dianion

Cited by 42 publications

References 34 publications

Schlenk's Biradical. – A Molecule in the Triplet Ground State

Schlenk's Biradical. – A Molecule in the Triplet Ground State

Counter-ion effects on the spin density distribution in triplet aromatic dianions

NMR Studies of 4n π-Conjugated Polycyclic Anions

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