Synthesis of large polycyclic aromatic hydrocarbons:: Variation of size and periphery

A new series of polycyclic aromatic hydrocarbons (PAHs) with different peripheries was synthesized via oxidative cyclodehydrogenation of suitable oligophenylene precursors under mild conditions. Such large PAHs are considered to be two-dimensional graphite sections whose electronic properties are expected to converge to those of macroscopic graphite. The synthetic buildup of the oligophenylene frameworks was mainly based either on Diels-Alder reactions or on cyclotrimerizations. They were subsequently converted into planar aromatic hydrocarbons containing up to 78 carbon atoms. Due to the insufficient solubility of extended PAHs, characterization was achieved by laser desorption/ionization time-of-flight mass spectrometry and UV/visible spectroscopy of thin films.