Supramolecular organogels based on perylenetetracarboxylic diimide trimers linked with benzenetricarboxylate

Two new perylenetetracarboxylic diimide (PDI) derivatives, namely, trimer 1 and trimer 2, composed of three PDI units with different tail groups, are prepared. Solubility of these two trimers is significantly different due to the different tail groups. The aggregation behavior of these two compounds in solution was investigated using absorption and fluorescence spectra. The results indicate that both trimers 1 and 2 can form large molecular aggregates via an intermolecular process in either good solvent or poor solvent. Trimer 1 can form gel in a mixed solvent of methanol and tetrahydrofuran (THF), while trimer 2 can only form gel in non-polar solvents, such as hexane and toluene. This can be ascribed to the multiple long alkyl chains in trimer 2, which have introduced extra hydrophobic interactions besides the pi-pi interactions between the molecules of trimer 2. The morphology examination of the dried gel of trimer 1 by atomic force microscopy (AFM) reveals simply long fibers. But, the dried gel of timer 2 shows network-like morphology, which can be ascribed to the hydrophobic interactions between the multiple alkyl chains.