Ultraviolet photoemission spectroscopic studies of six nanocyclic aromatic hydrocarbons in the gaseous and solid states

Abstract

Applying various synthetic methods, six nanocyclic aromatic hydrocarbons, violanthrene A (VEA), isoviolanthrene A (Iso VEA), violanthrene B (VEB), isoviolanthrene B (IsoVEB), tetrabenzoperylene (TBP) and tetrabenzopentacene (TBPA), have been prepared. Four of them, VEA, IscVEA, VEB and IsoVEB, have coplanar or fairly coplanar structures, whereas the other two, TBP and TBPA, have non-planar structures. Ultraviolet photoemission spectra of the six compounds were measured in the gaseous and solid states and the ionisation potentials and polarisation energies were determined. The gas-phase ionisation potentials are related to their molecular structures whereas the polarisation energies reflect the small molecular polarisability and the reduced molecular packing density of overcrowded molecules in the solid state.