Synthesis of Soft Octahedral Nanoparticles through Supramolecular Self-Assembly of C3-Symmetric Trinaphthylamine Trisamides.

Self-assembly of C3-symmetric triarylamine trisamide monomers has been recently studied in the literature, consistently leading to supramolecular polymers and materials with remarkable optical and electronic properties. As observed with other families of C3-symmetric monomers, their nucleation and growth mechanisms mainly rely on their one-dimensional stacking through highly directional hydrogen bonding. Now, we report the possibility of shifting their directing noncovalent interactions from hydrogen bonding to π-π and van der Waals interactions and, consequently, of shifting their self-assembly from one-dimensional fibrils toward two-dimensional smectic layers that further organize in purely organic octahedral nanoparticles. This dramatic structural change is simply achieved by extension of the aromatic core from phenyl to naphthyl units. Interestingly, the size of these soft supramolecular octahedra can be controlled between 200 nm and 50 μm by choosing the cooling rate used during the self-assembly process. By employing a comprehensive combination of experimental and theoretical tools, we fully elucidate the hierarchical mechanisms at work in the octahedrons' formation. These results highlight the potential tunability of C3-symmetric H-bonded monomers to generate original 3D supramolecular systems and materials.