Study On Synthesis And Spectroscopic Properties Of Porphyrin Derivatives Substituted By Aromatically Heterocyclic At β-Position

Porphyrin with unique large conjugated structure and spectral properties is a class of conjugated aromatic macrocyclic molecules with 18π electron.After structural modification,they have been widely used in the fields of photocatalysis,dye-sensitied solar cells(DSSCs)and photodynamic therapy.In this paper,a series of aromatically heterocyclic porphyrin derivatives were obtained by modifying the β-position of porphyrins.The optical properties and reaction mechanism of these derivatives were studied by means of UV-visible spectrum,fluorescence spectrum,singlet oxygen molecule yield and density functional theory.The structure-activity correlations between the new properties of modified porphyrin and β-position substituents was described systematically in this paper.which opens up a new direction for further development of porphyrins.The details are as follows:(1)Protoporphyrin dimethyl ester was used as starting material,then,three β-substituted protoporphyrin dimethyl ester derivatives was synthesized by 1,3-dipolar cycloaddition and coupling reaction at the β-position vinyl group.Spectral and singlet oxygen studies showed that compared with protoporphyrin dimethyl ester,the molar extinction coefficient of β-substituted protoporphyrin dimethyl ester derivatives was increased or the maximum absorption wavelength was redshifted,which improved the utilization of visible region.They have the potential to be used as photosensitizers for photodynamic therap because improving the utilization of visible light and maintaining a high singlet oxygen quantum yield.(2)Six kinds of ferrocene-porphyrin derivatives were synthesized from tetraphenylporphyrin by β-formylation,chlorination,coupling and so on.Spectral and singlet oxygen studies showed that compared with tetraphenylporphyrin,the absorption spectra of ferrocene-porhyrin derivatives were red shifted after the connection of ferrocene to the β-position of tetraphenylporphyrin by different bridging groups due to the enhanced of the conjugated structure.The fluorescence was quenched because of the rapid electron transfer between ferrocene and porphyrin.The singlet oxygen quantum yield is reduced due to the limited porphyrin excited state intersystem crossing caused by introduction of ferrocene and the degree of energy transfer was reduced.(3)Different unsaturated bond groups constructed at porphyrin β-position,were used as dipolarphiles systems for 1,3-dipolar cycloaddition reaction with nitrile oxide,and ten cycloaddition products were synthesized.It was found that the β-substituted vinyl porphyrin cycloaddition was high regioselectivity,single cycloaddition product was obtained,whereas the β-ethynyl porphyrins resulted in two cycloaddition products.Spectral and singlet oxygen studies show that the blue shift occurs due to the reduction of conjugation degree,after vinyl-substituted porphyrin cycloaddition,and the five-membered heterocyclic ring formed after β-ethynyl porphyrins cycloaddition has aromaticity,which leads to the red shift of the spectrum.At the same time,the β-isoxazolyl or isoxazolinyl substituted porphyrin has a good singlet oxygen yield,which has the possibility to be used as photosensitizer for photodynamic therapy.