Synthesis and Self-Assembly of a Discotic Oligo-Carboxylate Tetra-Porphyrin-Perylenebisimide Amphiphile

We report the synthesis of an amphiphilic tetra-porphyrin perylenebisimide (PBI) conjugate via four-fold Suzuki cross-coupling at the PBI ortho-position. Oligo-carboxylate Newkome-type G1 dendrons attached at the porphyrin periphery serve as polar head groups. Theoretical modelling corroborated the assumed planar discotic geometry. The amphiphile is very soluble in mixtures of basic water and THF, where it displays strong aggregation at high water content. Insights into the self-assembly process were obtained by tracking the individualization through THF addition using UV/Vis absorption spectroscopy. Here, a PBI-centred aggregation motif becomes evident. Further evaluation of the morphology via STEM and TEM imaging reveals that the assembly is guided by hydrophobic interactions as well as interactions of the carboxylates. These ortho-linked tetra-porphyrin PBI architectures fill a gap within the known families of porphyrin-PBI conjugates. Furthermore, the amphiphile is a valuable addition to the library of amphiphilic porphyrin-PBI conjugates, representing a discotic counterpart to the known calamitic architectures.