Synthesis And Aggregation Properties Of BF₂ And B,O-Chelated Aza-BODIPY Dyes

In recent years,Aza-BODIPY dyes have been used in photodynamic therapy and fluorescent probes due to their excellent photophysical properties such as high molar absorption coefficient,long absorption wavelength,and high stability.On the other hand,the aggregates of such functional dyes usually exhibit unique spectral properties,which expands the application value of this type of dyes.Therefore,it is of great significance for the related research on the aggregation behavior of Aza-BODIPY dyes.In this thesis,four Aza-BODIPY 1-4 dyes were designed and synthesized,and the structure of compounds were characterized by means of ¹H NMR,¹³C NMR and HRMS.The aggregation properties of the four functional dyes were further studied by UV/Vis absorption spectra,fluorescence emission spectra,infrared spectra and AFM.For Aza-BODIPY 1,the results show that the whole molecule is rigid due to the chelation of B and O,and the absorption and emission peaks move to the near infrared region.In H₂O/DMSO mixed solvent,Aza-BODIPY 1 molecules formed J-type aggregates with the maximum absorption wavelength of 812 nm.The morphology of the nanofibers was observed by AFM.The acid sensitivity of Aza-BODIPY 1 to trifluoroacetic acid was also studied.It was found that a new dye species 2·H⁺was formed under acidic conditions.For the amphiphilic dye Aza-BODIPY 2,it was found that there was a multi-channel aggregation behavior in methanol solution.The thermodynamics and kinetics of the three kinds of aggregates were studied by UV/Vis absorption and fluorescence emission spectra.The key thermodynamic parameters of the aggregates were obtained by fitting the variable temperature spectra with nucleation growth model or equal K model,and the dynamic transition process from metastable state to steady state was studied.The results show that under certain conditions,Aza-BODIPY 2 can form two kinds of metastable aggregates and one kind of stable aggregates in methanol solution,and both metastable states are products of off pathway.For the dyes Aza-BODIPY 3 and Aza-BODIPY 4,two different aggregates can be formed in methylcyclohexane solution.The intermolecular and intramolecular hydrogen bonding forces in the aggregates were further studied by infrared spectroscopy.It was proved that the Agg.I was caused by intramolecular hydrogen bonding between triazole and amide,while the Agg.II was caused by intermolecular hydrogen bonding between adjacent molecules through amide group.This thesis is of great significance for the study of supramolecular assembly behavior and property regulation of Aza-BODIPY dyes.