Concurrent Cooperative J-Aggregates and Anticooperative H-Aggregates

Area of Science:

• Supramolecular Chemistry
• Materials Science

Background:

• Understanding supramolecular self-assembly is crucial for designing functional materials.
• Competing assembly pathways can lead to diverse supramolecular structures and properties.

Purpose of the Study:

• To investigate the competing self-aggregation behaviors of an N-heterocyclic aromatic dicarboximide molecule.
• To elucidate the thermodynamic features and mechanisms of H- and J-aggregate formation.
• To explore the possibility of controlling self-assembly pathways through molecular design.

Main Methods:

• Experimental observation of self-aggregation under varying conditions.
• Mathematical modeling to simulate thermodynamic equilibria.
• Analysis of steric factors influencing molecular packing.

Main Results:

• H-aggregates formed via an anticooperative process under moderate driving force.
• H-aggregates transformed into J-aggregates through a cooperative mechanism with increased driving force.
• Mathematical model accurately predicted experimental observations.
• Anticooperative pathways favor low/medium oligomers, while cooperative pathways favor high polymers.
• Coexistence of both pathways suppresses high polymer formation unless high polymerization is achieved.
• Molecular modification successfully suppressed H-aggregation, favoring a single cooperative J-aggregation pathway.

Conclusions:

• The study reveals a unique interplay between anticooperative and cooperative self-assembly pathways.
• Sequential formation of H- and J-aggregates is driven by increasing self-aggregation force.
• Molecular design can selectively control self-assembly pathways, enabling targeted supramolecular structure formation.