| Endowed with aggregation-induced emission?AIE?characteristics,organic luminescent materials are practically weakly emissive or non-emissive when dispersed in dilute solution,but become highly emissive once aggregates are formed,which is ascribed to the process of restriction of intramolecular motions.This eccentric fluorescence behavior of AIE materials,whereby the aggregation of luminogens plays a positive role,surmounts aggregation-caused quenching drawback of traditional organic luminescent materials.And through introducing an AIE motif to the molecular design,not only are highly efficient solid-state luminescent materials readily achievable,but also we can take advantage of versatile chemical modification to realize the control of luminescence in diverse wavelengths.Therefore,the research on AIE-active materials has received ever-growing interest in recent years.Today,the applications of AIE materials have spread through many research domains,such as smart materials,optoelectronic devices,clean energy,biomedical engineering and real-time environmental sectors.The natural AIE process has a widespread influence in the human beings and the world,and far-reaching implications for the near future.It is most desperately needed to acquire a deep understanding of the AIE mechanism,to enrich and broaden the existing system of AIE materials,and to explore advanced high-tech functional applications of AIE materials.In this thesis,based on the mechanism of restriction of intramolecular motions,a series of novel AIE molecules decorated by phenothiazine,phenoxazine and crown ether have been designed and synthesized via simple palladium catalyzed Buchwald-Hartwig coupling reaction or Suzuki coupling reaction.In addition,cyclized polytetraphenylethenes have also been prepared through a simple palladium catalyzed Suzuki self-coupling reaction of tetraphenylethene.On the basis of good characterization of their molecular structures and systematically investigated of their optical and electrical characteristics,the relationships between the structures and properties have been studied.Furthermore,the potential technological applications in a broad range of fields including stimuli response materials,organic electroluminescent devices and chemical ion probes have been explored.The main research contents and conclusions of this thesis are as follows:?1?Two new D-A-structure diphenyl sulfone derivatives,namely DPS-4PTZ and DPS-4PXZ,linked to phenothiazine or phenoxazine in their N position,have been designed and synthesized via a simple palladium catalyzed Buchwald-Hartwig coupling reaction.Compared with phenothiazine unit,phenoxazine unit possessed stronger electron-donating capability,so DPS-4PXZ showed a narrower optical bandgap,and stronger ICT effect,as well as more obvious bathochromic shift on both absorption spectrum and emission spectrum than DPS-4PXZ.At the same time,the reasonable twisted conformation of molecules made both DPS-4PTZ and DPS-4PXZ exhibiting AIE properties.The fluorescence intensity of DPS-4PTZ was 18 folds higher when the water fraction reached 70%than that in pure THF solution.Similarly,the fluorescence intensity of DPS-4PXZ in 90%water fraction was a27-fold increase compared with that in pure THF solution.In addition,DPS-4PTZ displayed significant mechanoluminochromism with high color contrast under straightforward mechanical grinding.The fluorescence peak of DPS-4PTZ powder in the initial state was located at 485 nm.After full grinding,the fluorescence emission peak shifted to 545 nm,suggesting the emission spectral redshifts of 60 nm.And the emission color of well-ground powder changed from light green to pale yellow accordingly.After being fumed with chloroform or treated by annealing,the fluorescence of DPS-4PTZ powder could recover to its initial state,which suggested that such mechanoluminochromism behavior was reversible.X-ray diffraction analysis indicated that external mechanical stimuli changed the molecular packings of DPS-4PTZ,making its ordered crystalline structure transform into disordered molecular packing or amorphous state.?2?Using TPE unit as the building block,under the mild conditions of palladium catalyzed Suzuki self-coupling reaction,two novel target macrocyclic polytetraphenylethene dimer and trimer,namely TPE-2S and TPE-3S,have been obtained,respectively.Compared with the monomer that formed the macrocyclic ring,the absorption spectrum of TPE-3S showed slightly redshift,indicating that moderately twisted molecular conformation of TPE-3S extended the?-conjugated chains of TPE unit to some certain extent.Just like TPE,TPE-3S exhibited a significant AIE effect,which began to form aggregates when the water content exceeded 50%,indicating that the cyclized structure limited the movement of the phenyl group and lowered the solubility owing to the large rigidity,and the fluorescence intensity of TPE-3S was 121 folds higher when the water fraction reached 70%than that in pure THF solution.?3?A new targeted TPE derivative,namely TPE-BC,which was modified by benzocrown ether,has been prepared by a simple Suzuki coupling reaction.Compared with TPE unit,the absorption spectra of TPE-BC was redshifted 17 nm.At the same time,just like TPE unit,TPE-BC showed AIE characteristic:when the water content reached 99%,its fluorescence intensity was 380 times higher than that in pure THF solution.In addition,TPE-BC displayed mechanoluminochromism behavior under straightforward mechanical grinding.The fluorescence emission peak of TPE-BC powder in the initial state was 454 nm,and its fluorescence emission peak shifted to 472 nm after well grinding,suggesting the emission spectral redshifts of 18 nm.The luminescence color changed from blue to light green,accordingly.Moreover,the fluorescence of TPE-BC could recover to the initial state after annealing,showing a good reversibility of this mechanoluminochromism process.What is more,the fluorescence of TPE-BC had a selective response to barium ions.The continuous addition of barium ions would gradually quench the fluorescence.Selecting the water content of 90%of the luminous system as a research object,when the concentration of barium ions was up to 10-4 M,the fluorescence intensity of this AIE system was decreased by almost one quarter.Upon further addition of barium ions into the luminous system till the concentration of barium ions was increased to 0.2 M,the fluorescence of TPE-BC could be completely quenched,suggesting potential applications of TPE-BC as a chemical fluorescent probe to detect barium ion. |
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