Tetraphenylbenzene-based AIEgens:Synthesis And Applications

Since silole and TPE are found to be AIE active, a lot of functionalized derivatives based on them are developed for their great potential in real-world applications. The exploration of new AIE active cores plays a great role in the further development of AIE. This thesis is to develop a new series of AIE-active polyphenyl molecules. Besides, a series of D-A structured derivatives based on tetraphenylbezene as AIE active core, are designed and synthesized for applications in OLED device, chemosensors, mechanochromic materials and so on.Firstly, a series of AIE-active polyphenyls were designed and synthesized. The influence of the number and position of phenyl ring attached to the central benzene ring on the AIE property of the molecule were well unveiled. Furthermore, single crystal information was further utilized to understand relationship between the photo-physical behavior and molecular conformation. More importantly, this work removes the dispute of Z/E isomerization of double bond containing AIE molecules, which further proves the validity of RIR mechanism.Secondly, a tetraphenylbenzene-based molecule embedded donor and acceptor units with blue emission and high solid quantum yield was designed. The fabciated OLED with it as light-emitting layer shows high performance with turn on voltage (3.2 V), high external quantum yield (2.92%), well luminescence (4629 cd/m2) and pure CIE coordination (0.15,0.12). Moreover, the thermal analysis results show such molecule possesses high Td (up to 365 ℃) but no detactable Tg.Thirdly, a tetrapenylbenzene-based multifunctional AIE active molecule with amine and dicyanovinyl substitutes was designed and synthesized. It exhibits the easy transformation between crystalline and amorphous state in solids, endowing great mechachromic property with emission difference could be as large as 110 nm and good reversibility upon heat and solvent fuming. The notable intramolecular charge-transfer (ICT) effect brought by the electron donating and accepting units makes it highly emissive in low polar solvent such as CCl4 but none-luminescent in higher polar solvent such as DCM and CHCl3. Interestingly, mixing DCM or CHCl3 with CCl4 could adjust the emission color of molecule which makes it be able to detect the reaction degree of production of CCl4 by the means of methane chlorination. What’s more, it is sensitive to very low content of DCM and CHCl3, which also enables it to detect the purification of CCl4 of industrial grade. Besides, the dicyanovinyl group is of high reaction activity with hydrazine. The molecule is none-emissive in DMSO/water due to the strong ICT effect. After reaction, the ICT channel was broken, which awakes the emission of product. Here,1 equivalent of hydrazine could react with 1 equivalent of probe and the detection could finish within 3 min, and the sensory ability is selective. Thus, this molecule can be used as a probe for the detection of hydrazine with turn-on response containing high sensitivity and selectivity, and low background signals.At the end, an AEE molecule emitting orange fluorescence with cyanine attached to tetraphenyl-benzene through carbon-carbon double bond was synthesized. It was used as a turn-off fluorescence probe for cyanide with good sensitivity and selectivity. The reason why the luminescence of the probe was quenched after reaction with cyanide was studied by purifying the resultant after the detection reaction. That is, while molecule shows emission in solution due to AEE effect, the TICT and AIE behaviour of resultant quenches the original weak emission in the detection solvents sysems (DMSO/H2O= 9:1), that is why the probe is of strong luminescence but the resultant is of weak luminescence, which endows the probe with turn-off fluorescence response to cyanide.