Electron spin resonance study of the radical anions of substituted cyclooctatetraenes.  The effects of Jahn-Teller distortions and vibronic mixing

Hammons, James H.; Bernstein, M.; Myers, Rollie J.

doi:10.1021/j100478a022

Cited by 10 publications

(6 citation statements)

References 2 publications

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“…It has relevance in several physical, chemical phenomena in which the potential can be modeled as a two-state system [14], wherein one may identify two wells as two different states of a quantum particle. These applications range from hydrogen bonding [15], umbrella flipping of ammonia molecule [16,17], anomalous optical lattice vibrations in HgTe [18], proton transfer in DNA [19] to model brain micro-tubules [20], internal rotation [21], etc., to name a few. Physics of solid-state devices [22], solar cells and electron tunneling microscopes [22] constitute some other important applications.…”

Section: Introductionmentioning

confidence: 99%

Information entropy as a measure of tunneling and quantum confinement in a symmetric double‐well potential

Mukherjee

Roy

2015

Annalen der Physik

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Information entropic measures such as Fisher information, Shannon entropy, Onicescu energy and Onicescu Shannon entropy of a symmetric double-well potential are calculated in both position and momentum space. Eigenvalues and eigenvectors of this system are obtained through a variation-induced exact diagonalization procedure. The information entropy-based uncertainty relation is shown to be a better measure than conventional uncertainty product in interpreting purely quantum mechanical phenomena, such as, tunneling and quantum confinement in this case. Additionally, the phase-space description provides a semiclassical explanation for this feature. Total information entropy and phase-space area show similar behavior with increasing barrier height.

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Section: Introductionmentioning

confidence: 99%

Information entropy as a measure of tunneling and quantum confinement in a symmetric double‐well potential

Mukherjee

Roy

2015

Annalen der Physik

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“…5 Upon EPR analysis, CN-C 8 H 7 •reveals four large proton couplings from the evennumbered carbons, a small a H is exhibited by the psuedo-para proton, and even smaller splittings arise from the protons on positions 3 and 7. 5 This is consistent with the odd electron residing in the molecular orbitals (Ψs) represented in Figure 1.…”

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confidence: 99%

Transient [8]Annulenyl Carbanion from the Anion Radical of Bromo-[8]annulene

2004

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The anion radical of mono-bromo- [8]annulene was generated in the absence of ion association, and the EPRmeasured spin densities can be explained in terms of the odd electron occupying MOs:where n > 1. This anion radical subsequently disproportionates to its corresponding dianion and neutral molecule. The dianion then undergoes a loss of Br -, leaving the [8]annulenyl carbanion, which can abstract a proton from either HMPA or liquid ammonia. The pseudo-ortho-bromo-[8]annulenyl carbanion also loses Brto give [8]annulyne, which can be stabilized in the form of its anion radical. The g value of the anion radical of [8]annulyne indicates that the extra strain energy due to the presence of the triple bond causes the two highest occupied MOs (degenerate in the anion radical of [8]annulene) to be slightly split.

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“…The reduction of C 8 H 7 NCO under vacuum conditions in hexamethylphosphoramide (HMPA) at 293 K with sodium metal, or in THF (with 1 equiv of 18-crown-6) with potassium metal at 180 K, gives rise to an EPR spectrum that upon computer simulation reveals that the anion radical of a substituted [8]annulene had been generated, Figure . , The two larger a H ’s (4.13 G (2 Hs) and 4.37 G (2 Hs)) come from coupling to the four hydrogens on the even numbered carbons, while the smaller a H (2.295 G (3 Hs)) is from the hydrogens on the odd numbered carbons. Interestingly, the magnitude of these a H ’s would suggest that the substituent attached is a relatively weak electron-withdrawing group . These EPR results are consistent with the reduced D 8 h [8]annulene ring undergoing a Jahn–Teller distortion to a ring that has a planar D 4 h geometry with alternating long and short bond lengths. , …”

Section: Resultsmentioning

confidence: 99%

Tris-[8]annulenyl Isocyanurate Trianion Triradical and Hexa-anion from the Alkali Metal Reduction of [8]Annulenyl Isocyanate

Peters

Klen

2015

J. Org. Chem.

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The solution phase alkali metal reduction of [8]annulenyl isocyanate (C8H7NCO) yields an EPR spectrum, which reveals electron couplings to seven protons and only one nitrogen. Although this strongly suggested that the C8H7NCO anion radical was generated, experiments on the oxidized product reveal the actual reduced species to be tris-[8]annulenyl isocyanurate. Unlike the previously studied phenyl isocyanurate anion radical, the unpaired electron(s) is now localized within an [8]annulenyl moiety. Further exposure to metal results in the formation of an equilibrium mixture of trianion triradical and trianion radical species. The cyclotrimerization to form the isocyanurate is proposed to be driven by a reactive C8H7NCO dianion, which is produced from the large equilibrium disproportionation of the anion radical. Exhaustive reduction of the tris-[8]annulenyl isocyanurate with potassium in THF generates the first-ever observed hexa-anion of an isocyanurate. NMR analysis reveals that the polarity of the carbonyl bonds within this hexa-anion is augmented and is caused by the close proximity of K(+) ions, which are tightly ion paired to the three [8]annulenyl dianion rings. These preliminary studies on the reduction of C8H7NCO suggest that polymeric materials (e.g., polyisocyanates) made from this isocyanate might exhibit unique properties.

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Electron spin resonance study of the radical anions of substituted cyclooctatetraenes. The effects of Jahn-Teller distortions and vibronic mixing

Cited by 10 publications

References 2 publications

Information entropy as a measure of tunneling and quantum confinement in a symmetric double‐well potential

Information entropy as a measure of tunneling and quantum confinement in a symmetric double‐well potential

Transient [8]Annulenyl Carbanion from the Anion Radical of Bromo-[8]annulene

Tris-[8]annulenyl Isocyanurate Trianion Triradical and Hexa-anion from the Alkali Metal Reduction of [8]Annulenyl Isocyanate

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