Malonitrile-Functionalized Tetraphenylpyrazine: Aggregation-Induced Emission, Ratiometric Detection of Hydrogen Sulfide, and Mechanochromism

Development of new aggregation-induced emission (AIE) luminogens has been a hot research topic because they thoroughly solve the notorious aggregation-caused quenching effect confronted in conventional fluorogens and their promising applications in, for example, organic light-emitting diodes, chemo-and biosensors and bioimaging. Many AIE luminogens (AIEgens) have been prepared but most of them are silole, tetraphenylethene, distyrylanthracene, and their derivatives. In this work, based on the skeleton of tetraphenylpyrazine (TPP), a new AIEgen, named TPP-PDCV, is generated by functionalizing TPP with malonitrile group. TPP-PDCV can serve as a sensitive ratiometric fluorescent probe for detecting hydrogen sulfide with high speciality and low detection limit of down to 0.5 x 10(-6) m. The mechanism for such detection is fully investigated and deciphered. Unlike most reported mechanochromic AIEgens, which undergo turn-off or -on emission or emission bathochromic shift in the presence of external stimuli, TPP-PDCV exhibits an abnormal and reversible mechanochromism with hypsochromic effect. These indicate that TPP-PDCV possesses a huge potential for high-tech applications through rational modification of TPP core.