On the Way to Graphene: The Bottom-Up Approach to Very Large PAHs Using the Scholl Reaction

The Scholl reaction was adopted to synthesize the very large polycyclic aromatic hydrocarbons (VLPAHs) hexabenzocoronene (HBC), quaterrylene and dicoronylene as well as their nonalternant isomers. These molecules can be considered subsections of a graphene sheet since the radial diameter of HBC is 13.5 angstrom and the length of both quaterrylene and dicoronylene is about 17.9 angstrom Improved synthetic procedures of synthesis are presented, and the resulting VLPAHs were isolated and recognized from their characteristic electronic absorption spectra. The precursor PAHs used in the Scholl's synthesis where studied by differential scanning calorimetry (DSC), and the thermal behavior of the resulting VLPAHs was studied by thermogravimetric analysis and differential thermal analysis (TGA-DTA). The VLPAHs hexabenzocoronene (HBC), quaterrylene and dicoronylene show a trend to carbonization (growth of the laminar molecules into stacked and large graphene sheets) when heated slowly to high temperature in a nitrogen atmosphere.