Forever young: polycyclic aromatic hydrocarbons as model cases for structural and optical studies

Polycyclic aromatic hydrocarbons (PAHs) are popular research subjects due to their high stability, their rigid planar structure, and their characteristic optical spectra. The recent discovery of graphene, which can be regarded as giant PAH, has further stimulated the interest in this area. For this reason, the relationship between the geometric and electronic structure and the optical spectra of PAHs are reviewed, pointing out the versatile properties of this class of molecules. Extremely stable fully-benzenoid PAHs with high optical gaps are encountered on the one side and the very reactive acenes with low optical gaps on the other side. A huge range of molecular sizes is covered from the simplest case benzene with its six carbon atoms up to disks containing as much as 96 carbon atoms. Furthermore, the impact of non-planarity is discussed as model cases for the highly important fullerenes and carbon nanotubes. The detailed analysis of the electronic structure of PAHs is very important with regard to their application as fluorescent dyes or organic semiconductors. The presented research results shall encourage developments of new PAH structures to exploit novel materials properties. Copyright © 2010 John Wiley & Sons, Ltd.