Solvent‐Tuned Supramolecular Assembly of Fluorescent Catechol/Pyrene Amphiphilic Molecules. Issue 55 (7th September 2018) - Nador, F.
Abstract: The synthesis and structuration of a novel low‐molecular‐weight amphiphilic catechol compound is reported. The combination of a hydrophilic tail containing a catechol unit and a pyrene‐based hydrophobic head favors solvent‐tuned supramolecular assembly. Formation of hollow nanocapsules/vesicles occurs in concentrated solutions of polar protic and nonprotic organic solvents, whereas a fibril‐like aggregation process is favored in water, even at low concentrations. The emission properties of the pyrene moiety allow monitoring of the self‐assembly process, which could be confirmed by optical and electronic microscopy. In organic solvents and at low concentrations, this compound remains in its nonassembled monomeric form. As the concentration increases, the aggregation containing preassociated pyrene moieties becomes more evident up to a critical micellar concentration, at which vesicle‐like structures are formed. In contrast, nanosized twist beltlike fibers are observed in water, even at low concentrations, whereas microplate structures appear at high concentrations. The interactions between molecules in different solvents were studied by using molecular dynamics simulations, which have confirmed different solvent‐driven supramolecular interactions. Abstract : Reversible structures : Fluorescent catechol‐based hollow nanocapsules/vesicles are obtained through a simple procedure that involves the dissolution in organic solvents of a simple amphiphilic molecule (see figure) containing a pyrene head and catechol tail. A correlation between the interaction of pyrene moieties giving supramolecular structures and vesicle formation based on the concentration could be established through spectroscopic techniques, as well as electron and confocal microscopies. Dispersion of this compound in water showed the formation of fibrillar structures assigned to ground‐state aggregates. Finally, reversible formation of hollow nanocapsules/vesicles or fibril‐like nanostructures was obtained through successive cycles in MeOH/H2 O at high concentrations.