Self-assembly of photofunctional cylindrical nanostructures based on perylene-3,4:9,10-bis(dicarboximide)

A perylene-3,4:9,10-bis(dicarboximide)-based electron donor-acceptor monomer was designed to self-assemble using the synergistic effects of π-π stacking, microsegregation, and hydrogen bonding. The resulting aggregates were characterized in solution by small-angle X-ray scattering (SAXS), while the solid-state structure was probed by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The solution-phase assemblies were found to consist of 12 monomers arranged in either a face-to-face stacked pair of hydrogen-bonded hexagonal arrays or a two-turn helix. The SAXS data do not allow a clear distinction between these two cyclic motifs. These cyclic arrays grow to lengths of about 1 μm and form bundles of cylindrical structures in the solid phase. Aggregation is solvent dependent, with methylcyclohexane inducing aggregation and tetrahydrofuran disrupting it. The solution-phase photophysics of the dodecamer were probed by UV-vis, time-resolved fluorescence, and femtosecond transient absorption spectroscopies, revealing that formation of the dodecamer introduces an ultrafast electron-transfer pathway that is not present in the monomer.