Direct Synthesis of Hexa-peri-hexabenzocoronene on Au(111) Surfaces: Insights into Intramolecular Dehydrocyclization and Molecular Modification Strategies

Polycyclic aromatic hydrocarbons (PAHs) are widely used in materials science, optoelectronic devices, and supramolecular chemistry because of their unique extended π-conjugated structures. Among numerous PAHs, hexa-peri-hexabenzocoronene (HBC) is a prominent representative of the all-benzene structural building blocks. The synthesis of HBC using hexaphenylbenzene (HPB) is considered the most direct approach, requiring only intramolecular dehydrocyclization. In this study, we calculated the complete reaction pathway for the formation of HBC molecules from HPB molecules on the Au(111) surface. Our study revealed that HBC is formed by sequential phenyl coupling reactions with a maximum energy barrier of 1.86 eV. We also obtained the surface properties of the HPB and HBC molecules, including their charge distributions, migration barriers, and molecular aromaticity. Furthermore, using a 1,2-dibenzobenzene (DBB) model, we introduced para-position electron donor/withdrawing groups to regulate the phenyl coupling reaction. The results showed that this strategy effectively reduces the reaction barrier with electron-donating groups having a more pronounced effect. Our research reveals the influence of functional groups on molecular electronic properties and provides theoretical insights for the design of precursor molecules and surface synthesis strategies.