Synthesis of large polycyclic aromatic hydrocarbons: Variation of size andperiphery

A new series of polycyclic aromatic hydrocarbons (PAHs) with different peri pheries was synthesized via oxidative cyclodehydrogenation of suitable olig ophenylene precursors under mild conditions. Such large PAHs are considered to be two-dimensional graphite sections whose electronic properties are ex pected to converge to those of macroscopic graphite. The synthetic buildup of the oligophenylene frameworks was mainly based either on Diels-Alder rea ctions or on cyclotrimerizations. They were subsequently converted into pla nar aromatic hydrocarbons containing up to 78 carbon atoms. Due to the insu fficient solubility of extended PAHs, characterization was achieved by lase r desorption/ionization time-of-flight mass spectrometry and UV/visible spe ctroscopy of thin films.