Self-Assembly of Cholane-Phenanthrene-Cholane Trimers for Light-Harvesting Supramolecular Systems

The self-assembly of two isomeric amphiphilic cholane-phenanthrene-cholane trimers and the light-harvesting properties of the formed supramolecular assemblies in aqueous medium are presented. Distinct differences in the supramolecular nanostructures are observed based on the type of phenanthrene isomer used, as well as on the cooling rate applied during the thermal self-assembly process. A fast cooling rate results in the formation of 2D objects (nanosheets) with both trimers. In contrast, a slow cooling process results in the observation of 3D objects, with worm-like nanostructures for the self-assembled 3,6-disubstituted phenanthrene trimer and nanotubes for the 2,7-isomer. Upon doping with an acceptor chromophore, the supramolecular phenanthrene assemblies demonstrate efficient energy transfer. The presence of small quantities (6%) of a pyrene acceptor results in a fivefold increase in the quantum yield compared to the phenanthrene trimer alone, highlighting their potential as artificial light-harvesting complexes. This work underscores the versatility of amphiphilic phenanthrene derivatives as building blocks for light-harvesting supramolecular systems.