Design,Synthesis And Performance Research Of Novel Fluorescence Probe And Columnar Liquid Crystal Based On Tetraphenylethylene

In recent years,fluorescent materials have attracted extensive attention in the fields of chemical sensors,biosensors,light emitting diode and luminescent liquid crystal materials.However,the traditional fluorescent materials usually have serious fluorescence quenching（ACQ）phenomenon in the aggregate state,which seriously limits the practical application of fluorescent materials.In 2001,Tang Benzhong’s research group discovered a special molecule（1-methyl-1,2,3,4,5-pentaphenylsilane）,which has strong fluorescence emission in the aggregate state or solid state.The discovery opened the door to aggregation-induced luminescence.With the development of research,more and more AIE molecules have been constructed.Among them,tetraphenylethylene（TPE）is known as the star molecule in AIE because of its simple structure,easy modification,excellent luminescence performance,and good light stability.At present,tetraphenylethylene has been widely used in the fields of sensors,liquid crystal and adjusting the aggregation luminescence properties of ACQ molecules.Although much progress had been made,its research needs to be further expanded.For example,the sensors cannot perform multiple detection and accurately identify IIB metal ions at the same time.The molecular columnar self-assembly of tetraphenylethylene liquid crystal was seldom concerned.In view of the above problem,in this thesis,a series of novel AIE fluorescent probes based on tetraphenylethylene（TPE）have been designed and synthesized to detect folate,ⅡB metal ions and adenosine triphosphate（ATP）with high sensitivity and selectivity.Secondly,a new type of AIE liquid crystal molecule was constructed by introducing a variety of flexible chains into tetraphenylethylene to attain the columnar liquid crystals.Moreover,the circular polarization luminescence was achieved by the ordered spiral arrangement of liquid crystal molecules of tetraphenylethylene with multiple chiral alkyl chains.The main contents are as follows:In the first chapter,a series of crown ether bridged bis-tetraphenylethylene compounds were designed and synthesized.Their sensing ability to various biomolecules and metal ions showed that this probe had obvious response to folic acid.After recognition,the fluorescence was significantly enhanced,and the maximum emission wavelength showed blue shift from 480 nm to 464 nm.The detection limit of folic acid was 6.36×10^-7 mol/L.The probe has also been successfully applied to the detection of folic acid in test paper and real samples such as mung bean and spinach.It also has been successfully applied to the detection of folic acid in living cells.In the second chapter,a novel AIE fluorescent probe based on benzalazine was designed and synthesized.This probe has good selective sensing ability for Cu²⁺with the obvious quench of fluorescence.It also has selective sensing ability for Zn²⁺,and the fluorescence exhibited blue shift（the fluorescence color changed to orange）.In addition,by adding adenosine triphosphate to coordinate Cu²⁺,the fluorescence system returned to strong red fluorescence.The detection limits of Cu²⁺and Zn²⁺were 2.51×10^-7 mol/L and4.85×10^-7 mol/L,respectively.It was successfully applied to detect Cu²⁺and Zn²⁺in living cells.In the third chapter,thiourea bridged bis-tetraphenylethylene derivative was synthesized by the condensation reaction of formyltetraphenylethylene with dithiocarbazide derivative.This compound can simultaneously detect three metal ions(Zn²⁺,Cd²⁺and Hg²⁺)in the mixed solution.The fluorescence was enhanced by adding Hg²⁺.With the addition of Zn²⁺,the fluorescence emission is enhanced and the maximum emission wavelength showed blue shift,which makes the fluorescence turn green.When Cd²⁺was added,the emission intensity increased significantly and the fluorescence color changed from red to yellow.The detection limits of Zn²⁺,Cd²⁺and Hg²⁺were 8.22×10^-8mol/L,2.36×10^-7 mol/L and 3.43×10^-8 mol/L,respectively.The sensing strip of probe can detect three kinds of ions well.The probe was further applied to the detection of three kinds of ions in living cells.In the fourth chapter,a series of novel tetraphenylethylene aromatic acyl derivatives with 4,8 or 12 alkyl chains were designed and synthesized.The results show that these compounds have excellent AIE properties and ordered hexagonal columnar mesophase.The increase of alkyl chain number is beneficial to decrease the phase transition temperature and expands the range of mesophase temperature.The number of alkyl chains greatly influences the fluorescence emission.The liquid crystal molecules with 8alkyl chains show the strongest fluorescence emission.This work shows that the number of alkyl chains can regulate the mesophase and fluorescence emission.In the fifth chapter,novel cholesterol containing tetraphenylethylene derivatives with columnar mesophase were prepared.The introduction of cholesterol not only makes the compound present hexagonal columnar mesophase,but also transfers the chirality of cholesterol to the TPE nucleus through the liquid crystal spiral self-assembly,which makes the target compound be able to emit circular polarization luminescence effectively.The highest asymmetry factor g_lum in liquid crystal phase is as high as 8.83×10^-2.In the last chapter,cholesterol tetraphenylethylene perylene imide derivatives were prepared by modifying perylene imide with tetraphenylethylene containing cholesterol chain.The results show that there has fluorescence resonance energy transfer effect between tetraphenylethylene and perylene,which makes it emit strong red fluorescence in the aggregation state.At the same time,through the spiral self-assembly effect of liquid crystal molecules,the chirality is further transferred to the perylene nucleus,which emits circular polarization luminescence,and its g_lum reaches 1.5×10^-2.