Photoelectron spectra of 4-substituted stilbenes

Abstract

The photoelectron spectra of stilbene and 4-R-stilbene (R = CH3O, CH3, F, Cl, NO2) has been determined and the five highest Π ionization potentials assigned. By considering the stilbenes to be formally constituted by union of a styrene and substituted benzene the influence of substituent on molecular orbital energies gas been rationalized. The data suggest that the stilbenes exist in a planar or nearly planar configuration in the gas phase. CNDO/2 calculations have been performed on a wider variety of 4-R-stilbenes (R = NH2, CH3, OH, F, CN, CF3, NO2) and it is suggested that planar configurations also predominate for those stilbenes. First ionization potentials of some of the stilbenes are correlated with bromination and ozonolysis rate data.