Harnessing Hydrophobic and π-π Interactions to Manipulate Kinetics of Aqueous Self-Assembly for Tailorable Architectures and Functions

Precise control over molecular arrangements and interactions is crucial for advancing the structures and properties of π-systems. However, significant hydrophobic effects complicate the regulation of their aggregation pathways and kinetics in water, challenging the design of materials with optimizable attributes. Herein, we introduce a series of porphyrins, each featuring a short cationic chain differing only in linkage. This design achieves precise kinetic control of porphyrin aggregation in water by leveraging hydrophobic interactions, enabling customizable architectures and functions. Specifically, these porphyrins initially aggregate into kinetically trapped states, where more hydrophilic chain linkages weaken the H-type π-interactions without altering the aggregation mode. This destabilization, however, reduces the energy barrier for transitioning via an “on-pathway” route to thermodynamically stable states characterized by distinct J-type stacking and strongly enhanced excitonic coupling. Consequently, this kinetic regulation of aggregation pathways facilitates seed-induced supramolecular assembly of porphyrins, yielding ultrathin nanosheets with outstanding uniformity and water-solubility. Moreover, differences in π-stacking patterns and excitonic interactions between the kinetic and thermodynamic assemblies give rise to distinct photosensitization behaviors, selectively generating singlet oxygen and superoxide, respectively. This work harnesses the intricate aqueous aggregation pathways of π-systems and provides insights into optimizing their supramolecular structures and functionalities.