Abstract

A detailed study of the oxidative cyclodehydrogenation of two oligophenylene precursors resulting in large polycyclic aromatic hydrocarbons (PAHs) which contain up to 42 carbon atoms gave insight into the reaction course. This study confirmed that the reaction occurs exclusively in an intramolecular fashion without the formation of organic side products. X-Ray diffraction, selected area electron diffraction, and low-dose high-resolution electron microscopy were used to analyse the effect of heat treatment and sublimation on the morphology and crystal structure of large PAHs, hexabenzo[bc,ef,hi,kl,no,qr]coronene (HBC) and dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (DBPP). HBC crystallizes in the γ-motif, as has been determined from single crystals previously. The experiments showed that small crystals exhibit some characteristic distortions of the unit cell. DBPP also crystallizes also in the γ-motif, but due to the "double-bay area" in the periphery of the molecule channels with a diameter of about 4 Å are formed in the crystal.