Synthesis And Property Study Of Aza-BODIPY Organic Photosensitizer

In recent years,Boron-dipyrromethene（BODIPY）compound has developed rapidly,which has the advantages of high molar extinction coefficient,excellent fluorescence quantum yield,outstanding absorption coefficient,good photophysical and chemical stability,low cytotoxicity and easy for chemical modification.Therefore,it has successfully stood out from similar dyes and attracted extensive attention of scientific researchers.BODIPY has been widely used in solar cells,fluorescent probes,small molecule detection,living cell imaging and photodynamic therapy.Among them,aza-BODIPY can achieve significant red shift of absorption and emission bands to improve the photosensitivity without changing the photophysical properties of BODIPY.In this paper,several aza-BODIPY compounds（4a,5a,4b and 5b）were synthesized and their optical properties were investigated.The specific research contents are as follows:（1）Aza-dipyrrole compounds containing thiophene and N,N-dimethyl structural units were obtained through condensation,addition and ring closure,using 2-thiophene formaldehyde and 4-dimethylaminoacetophenone/acetophenone as starting materials.And then,the aza-dipyrrole compounds reacted with BF₃·Et₂O to obtain the target products.Meanwhile,the structures of the products were characterized by NMR and MS.It is found that the absorption and emission wavelengths of these aza-BODIPY molecules（4a,5a,4b and 5b）were in the near-infrared region through detecting the UV-Vis absorption and fluorescence emission spectra.The half peak widths of UV-Vis absorption and emission spectra were relatively small.These results suggested that aza-BODIPY molecules have good fluorescence properties,which is critical for photosensitizer.（2）The ability of the synthesized aza-BODIPY molecule to produce singlet oxygen was tested by using the reactive oxygen species（ROS）detection probe 1,3-diphenylisobenzofuran（DPBF）.It was found that DPBF showed a strong absorption in tetrahydrofuran（THF）solution,and there was no obvious change with time;When aza-BODIPY organic photosensitizer was added,the absorbance decreased remarkably upon illumination,indicating that DPBF reacted with singlet oxygen produced by photosensitizer.Furthermore,it was found that when the synthesized aza-BODIPY compound 5a was added,the absorbance decreased more significantly,which indicated that introducing aldehyde groups into aza-BODIPY molecule could effectively increase the yield of singlet oxygen.To sum up,the synthesized aza-BODIPY molecule can efficiently produce singlet oxygen,which is expected to be used in photodynamic therapy.（3）Hydrophobic aza-BODIPY and hydrophilic molecular chain（copolymer of propylene oxide and ethylene oxide（polyether F-127））were assembled into nano-photosensitizer.The optical testing revealed that the maximum absorption and emission wavelengths of the nano-photosensitizer are in the near-infrared region,which is important for reducing the interference of self-absorption and autofluorescence of substances in organisms,and improving the penetration depth and treatment efficiency.Similarly,the ability of the nano-photosensitizer to produce singlet oxygen was characterized based on ROS detection probe DPBF,and the results exhibited that it could effectively produce singlet oxygen.In short,the nano-photosensitizer can not only be dissolved in water,but also has good photosensitive properties and a high singlet oxygen yield.Above all,the assembled nano-photosensitizer has a broad application prospect in the field of photodynamic therapy.