The Design,Synthesis And Singlet Oxygen Studies Of BODIPY Compounds With Meso-aryl-substituted Electron Donating Groups

In this paper,the meso positions of BODIPYs were modified with different aryl groups to synthesize three series of different BODIPY compounds.Then,the photophysical and photochemical properties of these BODIPY compounds were measured.The first series of photosensitizers were modified with the different para-aminophenyl at the meso position.The second series of BODIPYs were modified with different aromatic rings at the meso position.The third series of BODIPYs were modified with different methoxy groups on the phenyl rings at the meso position.The above modifications of aromatic rings make them good electron donating groups which makes these BODIPYs produce PET/PCT effects from the lowest excited singlet state,and leads to generating singlet oxygen in polar solvents accompanied by strong fluorescence quenching.The photophysical and photochemical properties of the BODIPYs were studied by ultraviolet-visible absorption spectra,fluorescence emission spectra,fluorescence quantum yields,fluorescence lifetime,singlet oxygen formation and other experiments.It was found that the first series of BODIPYs were PCT based photosensitizers,the second series were PET based photosensitizers,the third series were also PCT based photosensitizers,and BODIPY 16 and 20 were CT based photosensitizers.It was also indicated that the occurrence of PET/PCT led to an increase in T₁ state,which in turn resulted an increase in singlet oxygen yields.It was also found that with the increase of electron donating ability of the aromatic groups,the efficiency of PET/PCT increased and the efficiency of singlet oxygen yield also increased;with the increase of solvent polarity,the fluorescence quantum yields decreased;and the steric hindrance effects of the aromatic rings and the methyl groups at the 1 and 7 positions hindered the rotation from the phenyl rings,which resulted in significantly higher fluorescence quantum yields and the quantum yields of singlet oxygen formation.The above results of photophysical and photochemical properties can be explained by PCT/PET.It was believed that the aromatic rings were electron donating groups which makes these BODIPYs good photosensitizer,and these BODIPYs can be used in the medical fields as photodynamic therapy reagents for cancer treatment.