Characterization of novel perylene diimides containing aromatic amino acid side chains

• We investigated the spectroscopic characteristics of a novel set of perylene diimides.
• We correlated the spectroscopic data to the formation of aggregates.
• We established that PDIs may be better suited for biomolecular applications.

Perylene diimide derivatives have attracted initial interest as industrial dyes. Recently, much attention has been focused on their strong π− π stacks resulting from the large PDI aromatic core. These PDI stacks have distinct optical properties, and provide informative models that could mimic light-harvesting systems and initial charge transfer typical of photosynthetic systems. The absorption property of PDI derivatives may be tuned from visible to near-infrared region by peripheral substitution. We have studied a new class of PDI derivatives with aryl substituents derived from the side chains of aromatic aminoacids (Tyrosine, Tryptophan and Phenylalanine). We have investigated their absorption and the fluorescence properties in a set of organic solvents and established their different tendencies to aggregate in solution despite their solubility. Most aggregation appears to be unordered. One PDI analogue (the one formed from Tyr) in Methanol, however, appears to form J-type aggregates. Based on our results the compounds appear to be promising for future investigations regarding the interaction of these dyes with biomolecules.

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