Multiynylbenzene-Silole Copolymer:Synthesis And Spectroscopic Studies

Multiynylbenzene, silole and conjugated multiynylbenzene-silole copolymer have been synthesized.1,3,5-tribromobenzene reacted with3-methyl butynol to afford1,3,5-tris(2-hydroxy-2-methyl-4-but-3-ynyl)benzene, then1,3,5-triethynylbenzene was obtained by the cleavage reaction of the compound in presence of potassium hydroxide and toluene. On the other hand, using4-iodoaniline and trimethyl silyl acetylene as raw materials,4-trimethylsiylethynyl iodobenzene was synthesized by diazo reaction and halogenation. Therefore,1,3,5-tris[(4-ethynylphenyl)ethynyl]benzene (6) was prepared by the reaction of the1,3,5-triethynylbenzene and4-trimethylsiylethynyl iodobenzene. As another multiynyl compound,9,10-diethynylanthracene (14) was also synthesized. Some factors affecting these reactions were also studied. At the same time,2,5-dibromo-1,1-dimethyl-3,4-diphenylsilole and2,5-dibromo-1,1-dihexyl-3,4-diphenylsilole has been synthesized. The polymerization between dibromosilole and1,3,5-tris[(4-ethynylphenyl)ethynyl]benzene or9,10-diethynylanthracene were discussed, and a kind of poly(aryleneethynylenesiloles): hyperbranched conjugated polymer (18) has been prepared by the Sonogashira reaction, its number-average molecular weight(Mn) is22839Da, and weight-averaged molecular weight (Mw) is94492Da. The structures of the polymer and intermediates were confirmed by IR,1H NMR and13CNMR.Thermal behaviors of the conjugated polymer (18) were studied by TGA/DSC, the results indicated that18possessed good thermal stability with only about5%weight loss in a N2atmosphere at temperature of265.7℃, corresponded DSC curve showed that it was an endothermic process. The results of spectroscopic studies showed that the polymer had an absorption peak (λABmax) at440nm for UV-Vis spectra, and a fluorescene emission peak (XFLmax) at520nm (excited at440nm). Polymer (18) possessed AEE effect induced by poor solvent H2O in its THF solution, with gradually addition of water, the intensity of PL decreasing and then increasing, when the content of H2O is below70vol%, ACQ effect plays a dominant role; If the content of poor solvent H2O exceeds70vol%, due to the restriction of intramolecular rotations (RIR), AEE effect is the dominant role. The polymer was used as fluorescent chemosensor for the detection of explosive with high sensitivity. Its Stern-Volmer emission quenching constant is2.58×10-2ml/μg for PA, and9.09×10-3ml/μg for TNT.