Correlation between photoelectron ionization bands and electronic levels in pyrazine

Muszkat, K. A.; Schäublin, J.

doi:10.1016/0009-2614(72)85069-3

Cited by 18 publications

(4 citation statements)

References 9 publications

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“…Both through-space and through-bond orbital interactions can stabilize molecules. − The energy inversions of the symmetric and antisymmetric nonbonding MOs in diazobicyclooctane (Figure ) and in pyrazine are illustrative. The ca.…”

Section: Resultsmentioning

confidence: 99%

Aromatic Transition States in Nonpericyclic Reactions: Anionic 5-Endo Cyclizations Are Aborted Sigmatropic Shifts

Gilmore

Manoharan

et al. 2012

J. Am. Chem. Soc.

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The transition states (TSs) of 5-endo-dig and 5-endo-trig anionic ring closures are the first unambiguous examples of nonpericyclic reactions with TSs stabilized by aromaticity. Their five-center, six-electron in-plane aromaticity is revealed by the diatropic dissected nucleus-independent chemical shifts, -24.1 and -13.7 ppm, respectively, resulting from the delocalization of the lone pair at the nucleophilic center, a σ CC bond, and an in-plane alkyne (or alkene) π bond. Other seemingly analogous exo and endo cyclization TSs do not have these features. A symmetry-enhanced combination of through-space and through-bond interactions explains the anomalous geometric, energetic, and electronic features of the 5-endo ring closure transition state. Anionic 5-endo cyclizations can be considered to be "aborted" [2,3]-sigmatropic shifts. The connection between anionic cyclizations and sigmatropic shifts offers new possibilities for the design and electronic control of anionic isomerizations.

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Section: Resultsmentioning

confidence: 99%

Aromatic Transition States in Nonpericyclic Reactions: Anionic 5-Endo Cyclizations Are Aborted Sigmatropic Shifts

Gilmore

Manoharan

et al. 2012

J. Am. Chem. Soc.

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“…EHT analysis predicted a substantial (>1 eV) splitting in the calculated levels with S (σ -S in Figure 1) higher in energy than A (A + σ* in Figure 1). This orbital interaction was later confirmed experimentally in 1 14,15 and 2, 16 using photoelectron spectroscopy. The concept of n-σ-n through-bond coupling was introduced to address the orbital splitting seen for 1-3.…”

Section: Through-space Vs Through-bond Interactionsmentioning

confidence: 61%

Does π−σ−π Through-Bond Coupling Significantly Increase C−C Bond Lengths?

1997

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Orbital effects ascribed to π-σ-π through-bond coupling are the result primarily of destabilizing filledfilled interactions; little to no mixing occurs between the antisymmetric π combination and σ*. The magnitude of through-bond coupling does not correlate with bond lengthening. Previous conclusions that through-bond coupling induces long bonds relied in some cases on poor X-ray data and/or inappropriate molecular orbital theories to deduce geometries. Comparison of semiempirical and empirical force field data as a test for through-bond coupling is unwarranted. Standard force fields underestimate the steric bulk of the benzene face, but addition of so-called "throughbond coupling" terms does not provide a physically significant measure of through-bond coupling.

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“…The width of lone pair peaks has been correlated with the percentage of atomic character of the associated orbital (222). Calculations have been performed to deduce the vibrational envelope of H2S"1" (120), and the fine structure in the spectra of formic acid (287) and pyrazine (218) has been reported. Lindholm's group have extended their studies on Rydberg series of small molecules with pyrimidine (136), pyrazine (135), pyridizine (137), s-triazine (134), and s-tetrazine (138).…”

Section: Discussionmentioning

confidence: 99%

Electron spectroscopy. Ultraviolet photoexcitation

Betteridge¹,

Williams²

1974

Anal. Chem.

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The period covered in this review is from late 1971 to late 1973. During that time, the Journal of Electron Spectroscopy and Related Phenomena has been introduced and become established. A non-mathematical guide to the technique and simplified approach to photoelectron spectroscopy (19), as well as a massive and invaluable conference proceedings (262) have been published. Many of the papers in the conference proceedings have been published separately, in which case we give the journal reference with a crospreference to the proceedings. A recent discussion of the Faraday Society was devoted to photoelectron spectroscopy. There have been comparatively few general reviews (33,73, 103,175, 197), but that of Hamnett, Orchard, and Cox is outstanding (161). It is detailed, critical, and deals with difficulties which are often glossed over or ignored, but unfortunately its coverage of the literature is only through 1970. A review of inorganic aspects has been prepared by DeKock and Lloyd ( 1 1 I ) .In general, it has been a period of consolidation during which many earlier ideas (especially those of D. W. Turner) have been re-examined and exploited, and many more compounds have been run. Taking a bird's eye view of the publications since the last review (32) we note the following trends: Several new instruments have been described and others are in the advanced design stage. Most permit heating of the sample and so many more compounds are accessible to the technique.The various branches of electron spectroscopy which were developed separately are now being used in combination. The Vacuum Generators' ESCA 3 has been specifically designed to allow the same sample to be examined readily in situ by UPS, X-ray photoelectron spectroscopy, Auger spectroscopy, and LEED.UPS has been applied to solids and surfaces. It has become increasingly common for UPS studies of a molecule to be complemented by several types of MO calculation.Simplified methods of interpretation of spectra based on the identification of characteristic localized orbitals have been critically examined and found valuable.The angular distribution of photoelectrons has attracted a lot of attention.On the negative, side, we feel that there has been an undue concentration of a few groups of compounds-uit., substituted benzenes, alkyl alcohols and halides, and simple silicon compounds. In several of these studies, there is a great deal of overlap and lack of reference to published work.A number of papers have been published in which the spectral data are limited to either a portion of the spectrum, showing just one or two bands, or a table of ionization potentials. Such limited information is rarely able to support the author's arguments. TECHNIQUEInstrumentation. There are a number of commercially available UV photoelectron spectrometers. Perkin-Elmer has developed the Turner design from the PS 15 prototype to the PS 18, which enables samples to be heated. The ESCA instruments of AEI, McPherson and Vacuum Generators, can be adapted to UPS, the last of these being ...

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Correlation between photoelectron ionization bands and electronic levels in pyrazine

Cited by 18 publications

References 9 publications

Aromatic Transition States in Nonpericyclic Reactions: Anionic 5-Endo Cyclizations Are Aborted Sigmatropic Shifts

Aromatic Transition States in Nonpericyclic Reactions: Anionic 5-Endo Cyclizations Are Aborted Sigmatropic Shifts

Does π−σ−π Through-Bond Coupling Significantly Increase C−C Bond Lengths?

Electron spectroscopy. Ultraviolet photoexcitation

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