Photoelectron spectroscopy and substituent effects in halonaphthalenes

The electronic structure of two isomeric dibromonaphthalenes (C10H6Br2) has been investigated by HeI/HeII photoelectron spectroscopy. The spectra were assigned by Green's functions calculations and comparison with the spectra of related dibromobenzenes (C6H4Br2). The analysis of π-orbital and halogen lone pair ionization energies, enabled us to determine the magnitude of bromine-bromine intramolecular interactions and distinguish between through-bond and through-space type interactions. We also discuss the halogen–halogen interactions in other polynuclear aromatics.