Graphene-like Molecules Based on Tetraphenylethene Oligomers: Synthesis, Characterization, and Applications

Abstract

Graphene-like molecules were prepared by oxidative cyclodehydrogenation of tetraphenylethene­(TPE) oligomers using iron­(III) chloride as the catalyst under mild conditions. All the oxidized samples can be separated effectively from the stepwise ring-closing reaction that highly related to the reaction time. For example, the model compounds obtained from the stepwise cyclization reaction show a regular red-shift in UV/vis absorption and photoluminescence (PL) spectra. This result reveals that the molecular conjugation length will extend with the stepwise ring-closing reaction going on. Interestingly, we successfully obtained a series of colorful luminogens with blue, cyan, and green emission during this stepwise and accurate ring closing process. Cyclic voltammetry measurements taken give the corresponding band gap, which supports the results obtained from optical spectroscopy. For the strong intermolecular interaction, our graphene molecules can self-assemble to form a red-colored and hexagonal fiber. Furthermore, some molecules exhibit piezochromic luminescence. The PL emission of the molecules before and after oxidation can be dramatically quenched by picric acid through the electron transfer and/or energy transfer mechanism, enabling them to function as chemosensors for explosive detection. In addition, fluorescence cell imaging studies proved their potential biological application