The origin of counter-rotating rim and hub currents in coronene

A current density pattern of a polycyclic π-system can be obtained as a superposition of all circuit currents, i.e., currents induced formally in all possible cyclic paths in the π system. Most circuits in coronene are diatropic (4n+2)-membered ones. In fact, all (4n+2)- and 4n-membered circuits are diatropic and paratropic, respectively. This is why this hydrocarbon sustains counter-rotating rim (diatropic) and hub (paratropic) currents when it is placed in a magnetic field. Thus, rim and hub currents in coronene are indivisible parts of many circuit currents. In contrast, the coronene tetracation/tetraanion sustains conrotatory diatropic rim and hub currents.