Edgar Heilbronner

The photoelectron spectrum of butatriene

Abstract Photoelectron spectra of butatriene (I), tetradeuterobutatriene (II), tetramethylbutatriene (III) and tetra- t -butyl- butatriene (IV) are reported and discussed. The four main bands of the spectra of I and II are assigned to ionization from the 1b 3g , 2b 3u , 1b 2u and 1b 2g molecular orbitals on the basis of molecular orbital calculations (ab initio with STO-3G and 4-31G bases and semi-empirical SPINDO) all of which lead to the electron configuration… (1b 2g ) 2 (1b 2u ) 2 (2b 3u ) 2 (1b 3g ) 2 . The first three bands of III and the first two of IV correspond to 2b 3g , 5b 3u , 2b 2u and 7b 3g , 12b 3u molecular orbitals respectively. The spectra of I and II also show an additional band which cannot be assigned to direct ionization of an occupied molecular orbital in the ground state configuration. it is suggested that this may arise from a cation state… (1b 2g ) 2 (1b 2u ) 2 (2b 3u ) 2 (2b 2u ) 2 B 2u . Such a state is correlated with the 2 B 3g cationic ground state by internal rotation but corresponds to a local maximum in the rotational potential. Some simple model calculations are presented of Franck-Condon factors for the internal motion corresponding to these states. These show a composite band of the general type observed. However, the observed vibrational spacings indicate that significant carbon skeletal as well as torsional changes take place on ionization.

The azo-chromophor as component in photo [2+2]-cycloaddition reactions synthesis, structure and pe-analysis of planar-parallel bisazo-molecules

Abstract In order to test for a photo [2+2]-cycloaddition between two azo-units a tetracyclic bisazo-compound (7) has been constructed, for which the X-ray analysis confirms a planar-parallel arrangement of the N 2 -units and transannular N-N-distances of 2.877 A and 2.821 A, resp. In preliminary photoexperiments N 2 -elimination predominates in 7; in the N-oxides 10/11, however, after direct excitation (λ = 254 nm) N 2 /N 2 O-metathesis (13/14 and 15, resp.) is observed.

Photoelectron spectroscopic assignment of symmetry to the ground state and first excited state of the 1,4-cyclohexadiene radical cation

Abstract The empirical correlation of the photoelectron spectra of 1,4-cyclohexadiene (molecule 4), 1, 4, 5, 8-tetrahydronaphthalene (molecule 5), 1, 4, 5, 6, 9, 1 0-hexahydroanthracene (molecule 6), and 1, 4, 5, 6, 7, 10, 11, 12-octahydronaphthacene (molecules 6) proves that the electronic ground state of these molecules is 2 B 1u , assuming that they have D 2 h symmetry. In particular this confirms previous predictions for 1,4-cyclohexadiene (molecule 4), for which the “inverted” orbital sequence 2b 1u (π) above lb 3g (π) had been proposed under the assumption that hyperconjugative “through-bond” interaction dominates the “through-space” interaction of the two semi-localized π-orbitals.

He (Iα) photoelectron spectra of some higher aromatic perfluoro compounds

Abstract He(Iα) excited photoelectron spectra, the inferred ionisation energies, and their assignment, are presented for perfluoro-benzene, -naphthalene, -anthracene, -phenanthrene, -pyrene and -acenaphthylene.

A photoelectron spectroscopic investigation of the electronic structure of trimethylsilylhaloacetylenes

Abstract The photoelectron spectra (He I excitation) of trimethylsilylacetylene M(H) and of the four trimethylsilylhaloacetylenes M(X) with X = F, Cl, Br, I hav

The ionisation energies of bent and twisted double bonds. Part I

Abstract The energies of the π orbital and the other molecular orbitals of ethylene have been calculated, using the ab initio STO-3G method, as a function of the three out-of-plane internal coordinates using a 33 complete factorial design. The analysis yields the significant terms needed for a complete description of the influence of the out-of-plane deformations of ethylene on its π−1 ionisation energies. In agreement with experimental evidence obtained from the photoelectron spectra of strained and twisted substituted ethylenes, it is found that the effect of nonplanar distortion upon the π-electron orbital energy is insignificant. This lack of sensitivity is due both to the small sizes of the individual contributions associated with each of the three internal coordinates and, in addition, to the compensation of such effects having opposite sign and/or the cross-terms between pairs of internal coordinates.

Preparative organic chemistry

Theoretical chemical dynamics: A tool in organic chemistry.- A new theoretical look at the inversion problem in molecules.- Ion solvation in mixed solvents.

1-Azabicyclo[4.4.4.]tetradec-5-ene

1-Azabicyclo[4.4.4]tetradec-5-ene, synhesized by a ring cleavage route, shows evodence of transannular alkene–amine interaction in its photoelectron spectrum and in its rapid reaction with acids to form the 1-azoniatricyclo[4.4.4.0]tetradecane ion.