Design,Synthesis And Property Study Of Novel A-π-D-π-A Fluorescent Dyes

Organic fluorescent dyes have important applications in bio-diagnostics and imaging,photodynamic therapy,organic optoelectronic materials,etc.Compounds based on intramolecular charge transfer（D-π-A）are important dyes structure,but traditional D-π-A fluorescent molecules such as coumarin,rhodamine have short absorption and emission wavelength,small Stokes shift and poor structural tunability.Therefore,it is important to develop new fluorescent dyes with excellent properties.In this paper,a series of new A-π-D-π-A fluorescent dyes with excellent photophysical properties have been designed and synthesized.The structure and properties of dyes have been analysed and summarised,and their application value has been explored,as follows:（1）A series of cationic dyes with symmetrical and asymmetrical structures based on the novel electron donor 9,9-dimethylacridine（DMA）has been designed and synthesized and their photophysical properties have been investigated.We modulation the photophysical properties of dyes through the regulation of terminal receptors successfully.The results showed that all dyes have large Stokes shift（up to 125 nm）,high quantum yield and long emission wavelength.Moreover,the extension of the conjugation and the introduction of heavy atoms allow for the red-shift of the absorption and emission wavelength.At the same time,the symmetrically dyes exhibited single-linear oxygen generation capability and have been successfully applied to cellular fluorescence imaging.（2）Based on the design strategy of solid fluorescent dyes,we have designed and synthesized a novel class of A-D-A solid fluorophores,we have effectively adjusted the energy gap between HOMO and LUMO of our dyes by introducing different heterocyclic donors and acceptors(DMA-CN:λ_em=620 nm,DMA-ISO:λ_em=723 nm).In addition,further redshift of the wavelength was achieved by introducing POZ and PTZ.The photophysical properties of the dyes showed that the partial structure exhibits red solid fluorescence and large Stoke shift,the ICT effect of the dyes was enhanced with the enhanced electron-absorbing ability of the end groups,and the improved electron supplying ability of the central heterocyclic ring also red-shifted the spectral region of the dyes.Meanwhile,the A-D-A molecule have outstanding photostability compared with the D-π-A type dyes.Moreover,based on the specific reaction of phenothiazine parent with HCl O,we investigated the respond of TZ-SN with HCl O.The results showed that TZ-SN was able to respond HCl O specifically,and the fluorescence signal showed a ratio change,TZ-SN was also applied to HCl O detection and imaging in living cells successfully.（3）Based on the advantages of high selectivity,sensitivity and specificity of fluorescent probe technology,we designed a fluorescent probe NQCl O using DMA and phenothiazine as fluorophores for the detection of NQO1 enzyme and HCl O.Experiments have shown that yellow fluorescent signal can be generated after response to NQO1 enzyme and a green signal can be generated after response to HCl O,this probe has been used in cellular imaging experiments successfully.