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

Toroidal conjugation is a unique way of 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 demonstrate the first example of 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. We investigated the existence of charge and exciton delocalization in the toroidal π-stacking array using various steady-state and time-resolved spectroscopies and found that the positive charge migrated in the toroidal π-stacking array in the cationic and photoexcited states.