Supramolecular organogels based on perylenetetracarboxylic diimide dimer or hexamer

Two new perylenetetracarboxylic diimide (PDI) derivatives, namely dimer 1 and hexamer 2 composed of two or six PDI units respectively, are prepared. The aggregation behaviour of these two compounds in solution was investigated using absorption and fluorescence spectra. The results indicate that hexamer 2 tries to form large molecular aggregates via an intermolecular process even in very dilute solution. But dimer 1 prefers to take a folded conformation with the two PDI units stacking in a face-to-face way via an intramolecular process. Infrared spectra revealed the presence of hydrogen bonding between the amide nitrogen and carbonyl oxygen in the molecular aggregates of dimer 1 and hexamer 2. The morphology of the dried gel of dimer 1 shows bundles of long fibres with very large aspect ratios. But hexamer 2 presents only small rod-like aggregates with small aspect ratio. This difference is likely caused by the competition between different driving forces for the molecular aggregation.