Non-alternant polycyclic aromatic hydrocarbons (PAHs) are of interest both in fundamental and applied sciences. This is exemplified by the fact that various (non)-alternant PAHs are identified as ubiquitous combustion effluents with genotoxic properties. In addition ionized derivatives of (non)-alternant PAHs are frequently proposed as the carrier for diffused interstellar bands and as precursors for fullerenes under flame conditions. In recent years a variety of (non)-alternant PAHs containing externally fused cyclopenta moieties (CP-PAHs) containing up to 60 carbon atoms, which were identified or proposed as abundant combustion effluents, have become accessible. Their availability enabled a systematic study of their physico-chemical, photophysical and biological properties. Both their magnetic (1H NMR) and optical properties (UV/Vis absorption and excitation/emission spectroscopy) have shown that the number as well as the topology of the cyclopenta (CP-) moieties along the central PAH core has a profound influence.
Current research focus is the study of excited state properties of these CP-PAHs and their ions using primarily the ab initio MRDCI method. Other methods, e.g., coupled cluster or perturbation theory approaches, are not excluded. Where required relativistic effects like spin-orbit coupling will be included. For this purpose the MRDCI techniques has to be enhanced significantly to allow a reliable description. The availability of such methodology will be of considerable interest for the study of spectroscopic properties of both closed and open shell large organic molecules in general. For selected cases the characters of the excited states will in addition be explored using ab initio Valence Bond Theory. At a later stage these investigation will be extended to catenated silicon compounds with interesting optical properties.


Last Modified: March 29th, 2010 / Zahid Rashid