Fluorescence Resonance Energy Transfer and Aggregation-induced Emission of 2-(4-(N,N-diphenylamino)phenyl)-9-(1-pyrenyl)tryptanthrin

Abstract

2-(4-(N,N-diphenylamino)phenyl)-9-(1-pyrenyl)tryptanthrin (T2PhNPh₂9Py), which has pyrene introduced at the 9-position of 2-(4-(N,N-diphenylamino)phenyl)tryptanthrin (T2PhNPh₂), where aggregation-induced emission (AIE) is observed, was synthesized and its photophysical properties were investigated. The aggregation properties of T2PhNPh₂9Py were studied using a mixture of THF (good solvent) and water (poor solvent) to create an aggregate state by increasing the water content. When excited at 340 nm in the pyrene absorption band of the energy donor (D) in fluorescence resonance energy transfer (FRET), at 0% water content, weak D-derived pyrene fluorescence was observed near 450 nm, but with increasing water content, the pyrene fluorescence gradually disappeared and the energy acceptor (A)-derived T2PhNPh₂ fluorescence increased near 650 nm. Therefore, T2PhNPh₂9Py was observed to have a combination of intra- and intermolecular FRET and AIE properties.