Emissive Features of Perylene Diimide Derivative with β-Cyclodextrin: Probing the role of inter and intramolecular interactions.

Perylene diimide (PDI) derivatives have been extensively explored as chromophoric dyes for functional organic materials. Here, the custom synthesized tyrosine appended perylene diimide (PDI-Tyr) derivative has shown strong aggregation in aqueous medium diminishing its emissive features, which was surpassed by the supramolecular interaction with β-cyclodextrin (β-CD). Complex formation between PDI-Tyr and β-CD, proposed from the absorption and emission studies, have been substantiated by the H-NMR, ITC and geometry optimization data. Time-resolved emission and transient absorption studies carried out on PDI-Tyr in the absence and presence of β-CD, revealed an excited state intramolecular charge transfer (ICT) process from the tyrosine moiety to the PDI core with a time constant of ~30 ps, and the same gets retarded on encapsulation of the tyrosine groups in the βCD:PDI-Tyr (2 : 1) complex and the kinetics slows down to ~480 ps, reviving the emissive features. The absence of a long lifetime component and the lower emission enhancement in the monomeric condition as compared to the phenyl alanine (PDI-Phe) derivative, emphasize the major role of the ICT process in PDI-Tyr, which subdue the features of intermolecular aggregation, establishing the tunability of the emissive properties with the customization of intra and intermolecular interactions.