Electronic and magnetic characteristics of polycyclic aromatic hydrocarbons with factorizable Kekulé structure counts.

The Kelcule structure count (K) for some types of polycyclic aromatic hydrocarbons (PAHs), such as fluoranthene and perylene, can be factorized into the product of those for two or more aromatic subunits. The ring-current map for these PAHs placed in a perpendicular magnetic field exhibits a substantial localization on aromatic subunits. We found that such localization of pi circulation is a characteristic of fairly small K-factorizable species in the neutral electronic state. Even in such a case, no single pi molecular orbital (pi MO) is associated with localized pi circulation. Apparent localization of pi circulation is caused by the superposition of currents induced by all occupied pi MOs. pi circulation is less localized in larger K-factorizable species.