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

TL;DR

Scientists created a new disc-shaped molecule that self-assembles in water and could be useful for materials science.

Contribution

A new discotic porphyrin-PBI conjugate was synthesized and shown to self-assemble via hydrophobic and carboxylate interactions.

Findings

The tetra-porphyrin PBI conjugate self-assembles into discotic structures in water-THF mixtures.

STEM and TEM imaging revealed the assemblies form randomly coiled sheets with regular structures.

Fluorescence quenching suggests efficient photo-induced charge transfer in the conjugate.

Abstract

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.

We report on the synthesis of a new amphiphilic tetra‐ortho‐porphyrin PBI pentad. The pentads are characterized by quenching of the fluorescence emission, indicating efficient photo‐induced charge‐transfer. The amphiphiles show solubility in basic aqueous solutions of THF, where high water contents lead to a PBI‐centered aggregation. TEM imaging reveals the morphology as randomly coiled sheets consisting out of highly regular assemblies.

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