Synthesis And Aggregates Emission Behaviors Of Stimuli-Responsive Indolo[3,2-b] Carbazole Derivatives

Stimuli-responsive fluorescent property means that the luminescence of materials can be changed under the stimulation of some external environmental factors(such as pressure,temperature,acid or base).The smart materials have exhibited important practical significance and extensive application prospect in information record,data storage and anti-counterfeiting trademark.The stimuli-responsive behaviors of some materials are due to the changes of the accumulation mode.However,there do not exist a unified theory to explain the phenomenon,due to the relationships of macroscopic property and microstructure of stimuli-responsive materials are fuzzy.Thus it is difficult to provide effective guidance for further design such materials with superior performance.Therefore,it is of great significance to study the influence of the microstructure,especially stacking modes of such materials on their photophysical properties.At present,there are two main ways to change the molecular packing mode.The first is to change the intermolecular forces through the stimulation of the external environment,thereby changing the photophysical properties of the material.The second is to change the electron clouds distribution of the molecule by introducing different functional groups,and adjust the energy levels of the ground state and the excited state to achieve a changeable in properties.In this thesis,a series of indolo[3,2-b]carbazole derivatives have been designed and synthesized based on thoroughly literatures' research.The molecular stacking structure and fluorescence emission of these compounds are the main research content,which are used to explore the relationship between molecular packing and photophysical properties.The detailed research contents are listed as follows:1.An indolo[3,2-b]carbazole derivative(Br-ICZ-CN)containing dicyanovinyl groups has been synthesized by Friedel-Crafts acylation reaction and Knoevenagel reaction.The photophysical properties in different polar organic solvents indicate that Br-ICZ-CN has an obvious intramolecular charge transfer(ICT)process,which is verified by density functional theory calculations.By studying the luminescence behavior of Br-ICZ-CN in a mixed solution of THF and water,it is found that,as the water contents(fw)are increased,the molecules are gradually aggregated,and the fluorescence intensity shows an increasing tendency.At fw =90%,the fluorescent intensity shows 20 times enhancement,indicating that Br-ICZ-CN possesses aggregation-induced emission enhancement(AIEE)properties.Under the grinding pressure,the fluorescence emission changes from yellow to orange-red,with the peak of emission band shifting from 553 nm to 592 nm,which can be restored to its original state under dichloromethane steam or heat.Powder X-ray diffraction(XRD)and scanning electron microscopy(SEM)results confirm that the transition between crystalline and amorphous states is the main reason of mechanofluorochromic property.2.Three indolo[3,2-b]carbazole derivatives(Br-ICZ-C4,Br-ICZ-C8 and Br-ICZ-C12)containing different alkoxy chains have been designed and synthesized.The compounds have strong fluorescent emission properties at the solid state,and the fluorescence quantum yields were more than 44%.This series of compounds exhibit solvatochromism effects in different polar organic solvents,and have AIEE properties in tetrahydrofuran and water mixed solvents.The maxium increase ratio in fluorescent intensity of the three compounds is 4.3,6.7 and 6.9 times,respectively.Differential scanning calorimetry(DSC)and polarizing optical microscope(POM)results show that the compound Br-ICZ-C12 existes multiple phase transition temperatures and shows responsiveness to thermal stimulation,and exhibits typical nematic liquid crystal characteristics at a certain temperature range.The introduction of dif'ferent lengths of carbon chains can effectively change the stacking mode of molecules and regulate the photophysical properties.3.4-Fluorophenyl and cyanostyrene functionalized indolo[3,2-b]carbazole derivatives(F-ICZ-H,F-ICZ-Br,F-ICZ-Ben and F-ICZ-CF3),3,5-difluorophenyl and cyanostyrene functionalized indolo[3,2-b]carbazole derivatives(2F-ICZ-H,2F-ICZ-Br,2F-ICZ-Ben and 2F-ICZ-CF3)have been designed and synthesized through introducing different substituent groups.The photophysical properties under different solvents indicate that these compounds exhibit typical ICT processes.The electron cloud transition process is analyzed by density functional theory.It is found that the substituent benzene ring)s at the 6,12-positions of indolo[3,2-b]carbazole are almost perpendicular to the indolo[3,2-b]carbazole group,and have little effect on the degree of molecular conjugation.Therefore,changing the group on the 6,12-position phenyl rings have a weak effect on photophysical properties of molecules in solutions.These compounds show AIEE character in THF and water mixed solvents,and the increases in fluorescent intensity are more than 5 times.The fluorescence emission spectra and the fluorescence quantum yield data at the solid state indicate that different substituent groups affect the molecular packing mode,thereby change the fluorescent preformance.After grinding,F-ICZ-CF3 exhibits stimuli-responsive emission,the color of fluorescence changes from yellow-green to yellow,with the band shifting from 508 nm to 536 nm,and can be restored under ethanol vapor.Powder XRD and SEM experiments exhibit that the chan,ge of the stacked structure is the main reason for the change of its fluorescent properties.4.Based on the results of fourth chapter,eight a-cyanostilbene modified indolo[3,2-b]carbazole derivatives(2F-ICZ-Ben-H,2F-ICZ-Ben-Br,2F-ICZ-Ben-Ben and 2F-ICZ-Ben-CF3;:F-ICZ-Ben-H,F-ICZ-Ben-Br,F-ICZ-Ben-Ben and F-[CZ-Ben-CF3)have been designed and synthesized through introducing phenyl groups at 4,10-pisitions of indolo[3,2-b]carbazole.The photophysical properties of these compounds in different polar organic solvents and aggregation conditions are studied.The results show that compared with the previous molecules,the introduction of the phenyl groups can retain the strong fluorescent emission at aggregated state,exhibit strong fluorescent emission in solution,and increase the fluorescence quantum yields at the solid state.Under the grinding pressure,the compound F-ICZ-Ben-CF3 exhibited stimuli-responsive fuorescent property,the fluorescence changes from yellow to orange-yellow emission,with the peak of emission band shifting from 548 nm to 572 nm,which can be restored to its original state under ethanol steam,powder XRD and SEM results confirm that the change of stacked structures is the main reason of mechanofluorochromic property.The above experiments reveal that the introduction of the phenyl groups can adj ust the stacking mode of such molecules,and it is easy to effectively increase the fluorescent emission.