Tetraphenylethenyl-modified perylene bisimide: aggregation-induced red emission, electrochemical properties and ordered microstructures

Perylene bisimides (PBIs) are one class of the most explored organic fluorescent materials due to their high fluorescence quantum efficiency, electron transport behaviour, and ready to form well-tailored supramolecular structures. However, they suffer from heavy aggregation-caused quenching (ACQ) effect which has greatly limited their potential applications. We successfully tackle this problem by chemical modification of the PBI core with two tetraphenylethene (TPE) moieties at the bay positions. This modification resulted in a pronounced fluorescence red-shift (over 120 nm) and rendered the derivatives (1,6-/1,7-DTPEPBI) with evident aggregation-induced emission (AIE) behaviour. Both 1,6-DTPEPBI and 1,7-DTPEPBI emit bright red fluorescence in the solid state. The fluorescence quantum efficiency of the aggregates of 1,7-DTPEPBI (Φ _{F, solid} = 29.7%, formed in a hexane/ dichloromethane mixture, f _h = 90%) is about 424 times higher than that in dichloromethane solution (Φ _{F, solut} = 0.07%). Electrochemical investigation results indicated that 1,7-DTPEPBI sustained the intrinsic n-type semiconductivity of PBI moiety. In addition, morphological inspection demonstrated that 1,7-DTPEPBI molecules easily form well-organized microstructures despite the linkage of the PBI core with bulky TPE moieties.