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1.
2.
The photoelectron spectra of the six propellanes 1 to 6 have been recorded. Those bands which correspond to ejection of an electron from a π-orbital have been assigned, using the concept of through bond and through space interaction. Homoconjugative interaction between the π-systems of the two butadiene moieties of 6 is of the same order as that of the π-orbitals in norbornadiene. 相似文献
3.
Wolfgang Marterer Horst Prinzbach Grety Rihs Jakob Wirz Jaques Lecoultre Edgar Heilbronner 《Helvetica chimica acta》1988,71(8):1937-1965
The propensity of the N?N bond to undergo photo [2 + 2] cycloadditions has been further explored. In the specifically designed 1,5-azo/enes 1–3 , no [2 + 2] cycloaddition has been observed upon either direct or sensitized excitation with light of various wave lengths at temperatures down to 77 K, in line with expectations based on X-ray ( 1 : d = 2.71 Å, ω = 129°) and PE measurements ( 1 : I1 = 8.00, I2 = 9.05 eV; 2 ; I1 = 8.00, I2 = 9.25eV). The steric/stereoelectronic demands for the participation of the N?N bond in pericyclic reactions are clearly more stringent than those for the C?C bond. 相似文献
4.
Manijeh Mohraz Wang Jian-qi Edgar Heilbronner Pierre Vogel Olivier Pilet 《Helvetica chimica acta》1980,63(3):568-570
The photoelectron spectrum of the title compound is reported and assigned by correlation with the photoelectron spectra of related molecules. 相似文献
5.
Photoelectron spectra of endo- and exo-cyclopropano-norbornene ( = endo- and exo-tricyclo[3.2.1.02.4]octa-6-ene) show that a significant homoconjugation exists between the π-orbital of the double bond and the symmetric Walsh-es-orbital of the cyclopropane ring in the exo-isomer, whereas the interaction is negligeable in the endo-derivative. 相似文献
6.
The experimental and theoretical basis of a recently proposed reassignment of the bands in the PE. spectra of pyridine, pyridazine, pyrimidine and pyrazine is discussed in detail. A characteristic feature of the derived orbital sequence is that it takes the ‘through-space’ and ‘through-bond’ interaction between the ‘lone pair’ basis orbitals explicitly into account. A simple parametrization of the orbital energies, based on HMO-type models for the π-orbitals and for the ‘lone pair’ linear combinations, yields excellent agreement with the observed band positions in the PE. spectra of s-triazine and s-tetrazine. Our new assignment is compared to those proposed previously. 相似文献
7.
Edgar Heilbronner Rolf Gleiter Toshihiko Hoshi Armin de Meijere 《Helvetica chimica acta》1973,56(5):1594-1604
To obtain further information concerning the interaction between Walsh-orbitols of ‘conjugated’ cyclopropane rings, the photoelectron spectra of the following compounds have been recorded: bicyclo[4.1.0]heptane 1 , cis- and trans-tricyclo[5.1.03, 5]octane 2, 3 , diademane 4 , trans-pentacyclo[3.3.2.02, 9.04, 10, 06, 8]decan 5 and bicyclo[4.1.0]heptene-2 6 . The first bands in the PE.-spectra of these compounds have been assigned on the basis of a ZDO HMO-approximation. For 2 and 4 the value for resonance integral between linked 2p atomic orbitals of two adjacent eclipsed cyclopropane rings is found to be ?1.73 eV. 相似文献
8.
Christopher Batich Edgar Heilbronner Martin F. Semmelhack 《Helvetica chimica acta》1973,56(6):2110-2112
For a given molecule M, the difference ΔI between the first two vertical ionization potentials Iv,2 and Iv,2 (from MOs ψ1 and ψ2) and ΔE between the corresponding singlet-singlet excitation energies E1 and E2 (transitions ψ?1 ←1, ψ?1 ψ2) are related by ΔE = ΔI- (J2,?1?J1,?1) ?2(K1,?1 ? K2,?1), using Koopmans approximation. A simple MO model suggests that under certain conditions of symmetry and quasi-alternancy (e. g. in spiro[4,4]nonatetraene 1 ) the bracketed differences between the Coulomb- and exchange-integrals should vanish to first order, thus leading to the simple (almost) equality ΔE = ΔI. It is shown that the results from a photoelectron- and electron-spectroscopic investigation of 1 support this conclusion i.e. ΔI = 1.23 eV, ΔE = 1.19 to 1.23 eV. 相似文献
9.
Wolf-Dieter Fessner Gottfried Sedelmeier Lothar Knothe Horst Prinzbach Grety Rihs Zhong-Zhi Yang Branka Kova
Edgar Heilbronner 《Helvetica chimica acta》1987,70(7):1816-1842
‘Face-to-Face’ Benzo-anellated Homologous Hypostrophenes. Syntheses, X-Ray-Structure Analyses and PE Spectra ‘Face-to-face’ Benzo-anellated homologous hypostrophenes (series M ), of interest as substrates for [6 + 6]-photocycloaddition reactions, have been synthesized. From X-ray structural analyses of 13b and 13c shortest C? C distances of 2.80(2.76)/2.71 Å and interorbital angles (ω) of 129° (128°)/130° between the benzene rings have been determined. The PE spectra are discussed in the context of transannular π,π interactions. 相似文献
10.