Synthesis and Spectral Properties of Water-Soluble Phthalocyanine-Based Photosensitizers

With 3-nitrobenzonitrile and 3-mercapto-1-propanesulfonate as the starting materials, three kinds of water-soluble phthalocyanines with four 3-sulfopropylsulfonyl groups were synthesized by tetracyclization in the presence of metal acetate. The photophysical properties were measured by UV-Vis absorption spectra, fluorescence spectra and so on. The fluorescence quantum yield and the singlet oxygen yield were calculated. Compared with ZnPc, the shape of the fluorescence emission spectrums of the water-soluble phthalocyanines synthesized by introducing electron-withdrawing groups did not change, but the maximum fluorescence emission wavelengths had more than 10 nm red shifts. Among the three kinds of water-soluble phthalocyanines, zinc phthalocyanine had the highest fluorescence quantum yield and copper phthalocyanine had the lowest fluorescence quantum yield. Their fluorescence in aqueous solution showed a double exponential decay, which could be attributed to the protonation or deprotonation of excited states. The singlet oxygen quantum yield of zinc phthalocyanine was maximum, followed by hollow phthalocyanine, and copper phthalocyanine was minimum. The results of spectral analysis showed that the synthesized zinc phthalocyanine and hollow phthalocyanine have high singlet oxygen quantum yield and high photostability and are expected to be used as photosensitizers for photodynamic therapy and photoimmunotherapy.