Unraveling pathway complexity in the supramolecular polymerization of Z‑shaped perylenediimides: from kinetic H‑Aggregates to thermodynamic null supramolecular polymers

Abstract

This work reports the synthesis of Z-shaped PDI (Z-PDI) 1 and explores its self-assembly behavior. The lateral trialkoxybenzamide moieties in compound 1 promote the formation of metastable monomeric units (M*) through intramolecular hydrogen bonds, which undergo kinetically controlled supramolecular polymerization. This process exhibits pathway complexity, yielding H-type aggregates (AggIH) under kinetic control and, remarkably, null aggregates (AggIIn) under thermodynamic control. The conversion follows a competitive pathway, in which both aggregated states compete for the free monomeric species. A combination of experimental data and theoretical calculations reveals that the formation of AggIH is governed by the intermolecular hydrogen bonding between amide groups and the π-stacking of the aromatic cores. The thermodynamically favored null aggregate AggIIn also arises from the same noncovalent interactions but its unique nature stems from a balance between Coulombic and charge-transfer interactions similar in magnitude yet opposite in sign, resulting in an optical absorption profile nearly identical to that of the monomer. The living supramolecular polymerization of Z-shaped PDI 1 enables the transition from kinetically trapped to thermodynamically stable aggregates. These findings highlight the critical role of the molecular design in achieving null aggregation and pathway complexity, while emphasizing the importance of π-overlap, intermolecular distance, and chromophore orientation in determining the nature of the resulting supramolecular assemblies.