Conformational Analysis by Photoelectron Spectroscopy

Klessinger, Martin; Rademacher, Paul

doi:10.1002/anie.197908261

Cited by 42 publications

(10 citation statements)

References 96 publications

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“…In addition, 2,2'-dichlorobiphenyl was The status of the electron-diffraction measurements in the gas phase has been reviewed (16). A general review of principles and applications of conformational analysis by PES has been published (17). Table 2 lists the experimental data for those compounds, studied in the present work, for which no electron-diffraction data are available.…”

Section: Resultsmentioning

confidence: 99%

Inter-ring dihedral angles in polychlorinated biphenyls from photoelectron spectroscopy

Dynes¹,

Baudais²,

Boyd³

1985

Can. J. Chem.

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A proposal that the physiological activity of a chlorinated biphenyl is related to its degree of molecular planarity is explored through experimental measurements of inter-ring dihedral angles in the gas phase. A known correlation between the difference between fourth and first ionization energies of substituted biphenyls (via photoelectron spectroscopy), and the thermally averaged inter-ring dihedral angle as established by electron diffraction techniques, is confirmed and exploited for the present purpose. The expectation, based on both qualitative and quantitative theoretical considerations, that increased ortho substitution causes an increase in inter-ring angle, is confirmed. However, the observation that, for 2,2'-substituted halobiphenyls the only observed conformation is the near-syn form, is not easy to explain, and is discussed in terms of a non-bonding attractive force between halogen atoms. 1292 (1985). Faisant appel aux mesures expCrimentales effectuCes en phase gazeuse des angles ditdres entre les cycles, on a Ctudik I'hypothkse suggCrant que I'activitC physiologique des biphCnyles chlores est relike a son degrC de plankaritt molbculaire, Dans cette Ctude, on a confirm6 et exploit6 la corrklation connue qui existe entre les quatrikme et premikre Cnergies d'ionisation des biphtnyles susbtituks telles que mesurkes (via la spectroscopie photoClectronique) et I'angle dikdre inter-cycle ponder6 thermiquement tel qu'Ctabli par les techniques de diffraction Clectronique. En se basant sur des considkrations thCoriques tant qualitatives que quantitatives, on peut prCvoir qu'une augmentation de la substitution en position ortho provoquera une augmentation de l'angle inter-cycle; nos rksultats confirment cette hypothkse. Cependant, on ne peut pas expliquer facilement le fait que, dans le cas des biphknyles halogCnks substituees en positions 2,2', la forme quasi-syn est la seule conformation observke. On en discute en fonction d'une force attractive non liee entre les atomes d'halogknes.[Traduit par le journal] Introduction Maier and Turner ( I ) showed how the dihedral angle between the two rings of a series of gaseous biphenyls is related to the difference in ionization energies for electrons in the n3 and n6 molecular orbitals. This difference between fourth and first ionization energies was shown (I) empirically to vary linearly with cos 0, where 0 is the inter-ring dihedral angle determined by electron diffraction. The qualitative trends observed were satisfactorily accounted for (1) by simple analogies drawn with the molecular orbitals (MO's) of substituted benzenes, as determined (2) by photoelectron spectroscopy (PES). The linear correlation between AE(n3 -n6) and cos 0 was satisfactorily accounted for (1) by an ingenious analysis of the n-MO's described by a Huckel approach using as basis set the semi-localized n-MO's of the phenyl moieties, in place of the more usual atomic orbitals. Together with a frozen-orbital (Koopmans' theorem) assumption to permit identification of an orbital energy with the n...

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Section: Resultsmentioning

confidence: 99%

Inter-ring dihedral angles in polychlorinated biphenyls from photoelectron spectroscopy

Dynes¹,

Baudais²,

Boyd³

1985

Can. J. Chem.

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“…Both by computational [8 -16] and experimental [9,[17][18][19][20][21][22][23][24][25][26] methods the coplanar conformation is found to be the most stable and mesomeric effects are generally recognized as an important stabilizing factor. Ortho-dimethoxybenzene, on the other hand, has two methoxy groups in vicinal positions on the benzene ring.…”

Section: Introductionmentioning

confidence: 99%

From anisole to 1,2,4,5‐tetramethoxybenzene: Theoretical study of the factors that determine the conformation of methoxy groups on a benzene ring

Velde

Bultinck

Tersago

et al. 2006

Int J of Quantum Chemistry

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Unhindered ortho-dimethoxy-substituted phenyl rings often display a coplanar conformation. A theoretical study of a series of methoxybenzenes consisting of methoxybenzene (anisole), the three dimethoxybenzenes, and 1,2,4,5tetramethoxybenzene, at the DFT/B3LYP/6-311ϩϩG** level of theory, allows us to identify the factors influencing the conformational preference and attribute the coplanarity of such methoxy groups to mesomeric effects.As the number of methoxy groups in the molecule increases, the number of competing interac-VANDE VELDE ET AL.

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“…The phenomenon of conjugation between two cyclopropyl fragments is the subject of extensive studies 46 . Figure 2 represents the orbitals resulting from this interaction.…”

Section: Conjugation Between Cyclopropyl Fragments and Its Influementioning

confidence: 99%

“…The conjugation between cyclopropyl fragments does not affect the UV spectra of the corresponding molecules; however, it is manifested in their photoelectron (PE) spectra. Rotation of cyclopropyl fragments in nonrigid molecules like bicyclopropyl makes their PE spectra complicated, due to contribution from different conformers 46 . Consequently, the fixation of a conformation in SPC possessing adjacent three-membered rings makes these compounds perfect models for conjugation studies.…”

Section: Conjugation Between Cyclopropyl Fragments and Its Influementioning

confidence: 99%