Straightforward intra/intermolecular cyclization to AIE-active cyclic TPE: selectively distinguishing benzaldehyde and a temperature sensor

Abstract

A series of novel aggregation-induced emission (AIE) cyclic tetraphenylethene (TPE) compounds were successfully constructed by straightforward intra/intermolecular cyclization. These cyclic TPE were formed with a bridging moiety, such as alkyl or polyfluoroalkyl linker, between two TPE moieties. They displayed a variety of reversible mechanofluorochromic (MFC) behavior. Interestingly, the intramolecular cyclization product 361H exhibited a higher fluorescence quantum yield (Φ_F) than its intermolecular analogue 362H, offering a meaningful and accessible approach for facilely increasing Φ_F of TPE by intramolecular cyclization. Notably, the fluorinated cyclic TPE, 341F, doped into a poly dimethyl silicone (PDMS) film could selectively distinguish benzaldehyde from benzene, toluene, phenylcarbinol, and benzoic acid, accompanying visibly significant switching in emission color from cyan to black. Furthermore, 361F could exhibit an evident change in emission color from navy blue to green-yellow at 140 °C and gradually vanished at 180 °C. Thus, such diverting cyclic TPE could be potentially applied as a distinguishing test strip of benzaldehyde from toluene derivatives and as a temperature sensor.