Intermolecular Toroidal Conjugation: Circularly Stacked 16 π‐Planes Formed by Supramolecular Assembly Enabling Cyclic Charge and Energy Delocalization

Toroidal conjugation is a unique mechanism for charge and exciton delocalization via through-space overlap among circularly stacked π-orbitals, but the examples have been limited to intramolecular phenomena, where π-planes are arranged around a hub molecule. In this study, we extend this concept to intermolecular phenomena and provide strong evidence for intermolecular toroidal conjugation in designed systems, in which a circular π-stacked array is formed by molecular self-assembly. X-ray single-crystal analysis unequivocally revealed a toroidal array of 16 π-planes formed by the supramolecular dimerization of phthalocyanines substituted with eight pillar-like diazapentacenes interdigitating their π-pillars. The experimentally determined interplanar distances in the toroidal π-stacking array were close enough to realize through-space conjugation. Various steady-state and time-resolved spectroscopies, supported by theoretical calculations, indicated the possibility of positive charge migration within the toroidal π-stacking array in the cationic and photoexcited states.