Structural and electronic properties of linear and angular polycyclic aromatic hydrocarbons

• The structural and electronic properties of linear and angular PAHs are studied.
• The HOMO–LUMO gaps of linear and angular PAHs are inversely proportional to their width and length.
• The angular PAHs always exhibit larger HOMO–LUMO gaps than their linear isomers.
• The frontier orbitals of HOMO and LUMO exhibit different behavior in linear and angular PAHs.

The structural and electronic properties of linear and angular polycyclic aromatic hydrocarbons (PAHs) have been studied by ab initio calculations. We show that the HOMO–LUMO gaps of linear and angular PAHs are inversely proportional to their width and length and angular PAHs always exhibit larger HOMO–LUMO gaps than their linear isomers, indicating the relative higher kinetic stability for angular PAHs. The frontier orbitals of HOMO and LUMO are localized at the zigzag edges in linear PAHs, while they are distributed uniformly over the molecules in angular PAHs. These results offer key insight for understanding the size and topology depending effects, which is of great use for experimental syntheses of PAHs with specific electronic properties.