2,5-bis(4-alkoxycarbonylphenyl)-1,4-diaryl-1,4-dihydropyrrolo[3,2- b]pyrrole ( AAPP) AIEgens: tunable RIR and TICT characteristics and their multifunctional applications†

Abstract

Novel propeller-like AIEgens with tunable emission were readily prepared and used as a fluorescent thermometer and selective chemosensor for Cd( ii) detection.

Abstract

Aggregation-induced emission luminogens (AIEgens) have attracted extensive interest for their outstanding luminescence properties in the aggregated state and even in the solid state. In this work, we developed a series of novel AIEgens based on 2,5-bis(4-alkoxycarbonylphenyl)-1,4-diaryl-1,4-dihydropyrrolo[3,2- b]pyrrole ( AAPP). The AIEgens can be facilely synthesized through a single-step reaction under mild conditions with satisfactory yields. Interestingly, AAPP was found to have multiple luminous mechanisms that result in variable fluorescence properties. The propeller-like structure of AAPP enables a restricted intramolecular rotation (RIR) process which significantly enhances its fluorescence in the aggregated state ( i.e. AIE fluorescence). In addition, there is a donor–acceptor interaction between the heterocycle center and the alkoxycarbonyl units in AAPP which allows a typical twisted intramolecular charge transfer (TICT) process in the dispersed state, resulting in strong fluorescence emissions in non-polar or low-polarity solvents but fluorescence quenching in high-polarity solvents. Due to the tunable RIR and TICT processes and the multiple fluorescence, AAPP compounds exhibit multifunctional applications: (1) as a reversible fluorescent thermometer, AAPP exhibited excellent fatigue resistance. There was a good linear relationship between its fluorescence intensity and temperature from 10 °C to 60 °C. (2) The desethyl AAPP derivative ( CAPP) was successfully applied in the detection of Cd( ii) in aqueous solution at neutral pH, and showed a 500-fold fluorescence “turn-on” response to Cd( ii) with good selectivity.

Notes

†Electronic supplementary information (ESI) available: Selected spectra and data referred to in the paper. CCDC AAPP ( 1561488) and AAPP-CF3 ( 1561489). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc03076b