PHOTOELECTRON HE-1 SPECTRA OF FLUORINATED AZO-BENZENES AND AZOXY-BENZENES

The electronic structure of azobenzene, C6H5N=NC6H5, azoxybenzene, C6H 5N(O)=NC6H5, and their fluorinated derivatives, including some fluorin ated azobenzenes with substituents in the para position (X = CH3, OCH3 , CF3, CN, NO2, Br), have been studied by photoelectron spectroscopy. Spectral interpretation has been carried out using quantum-chemical MN DO calculations and literature data regarding the electronic structure of related compounds. In the spectra of the azobenzenes, a group of b ands lying in the range of low ionization energies corresponds to four pi-orbitals of the benzene rings and one sigma-orbital localized on t he N=N bond. For azoxybenzenes, a similar group of bands refers to fou r pi-MOs and one orbital of an oxygen electron lone pair. The contribu tion of fluorine orbitals to the upper occupied pi-MOs is small and th e changed energy of these orbitals may be explained mainly by the indu ctive effect.