Photo-induced charge-transfer complex formation and organogelation by a tripeptide

Abstract

A terminally protected tripeptide Boc–Phe–Phe–Tyr–OMe 1 and picric acid form a photo induced charge-transfer complex and organogels. The interactions between stacked aromatic units play a key role in the assembly process. UV light (366 nm) has been used as a source of energy to cleave and homogenize π-stacking in the supramolecular arrangement of peptide 1 and picric acid. CD, FT-IR, NMR and powder X-ray diffraction studies exhibit distinct structural changes before and after light irradiation. Field emission scanning electron microscopy of the xerogels reveal a morphological change caused by photo induced charge-transfer complex formation. The fluorescence spectroscopy as well as confocal microscopy studies show that these charge-transfer complexes have a significant red emission at 672 nm.