UV photoelectron spectroscopy and 0uter valence electronic Structure of dihalobenzenes

The electronic structures of nine dihalobenzenes (C6H4FX; X = Cl, Br, I) have been studied by UV photoelectron spectroscopy (UPS) and assigned by comparison with the reported spectra of monohalobenzenes (C6H5X; X = Cl, Br, I). and quantum chemical calculations. Our results show that the fluorine substituent modifies energies of π- and halogen lone pair orbitals to a significant degree depending on its location (topology). We also demonstrate that the inductive effect of fluorine atom on the benzene ring can be readily observed and interpreted.