Syntheses and properties of octa-, tetra-, and di-hydroxy-substituted phthalocyanines

The synthesis and photophysical properties of a new series of zinc(II) phthalocyanines (ZnPcs) bearing multiple hydroxy and tert-butyl groups are reported. The X-ray structures of two phthalonitriles and one ZnPc are presented. All hydroxy-substituted ZnPcs show low fluorescence quantum yields in DMSO and complete fluorescence quenching in aqueous solutions, but high singlet oxygen quantum yields in DMSO (0.2-0.7). Our results suggest that the tetra- and octa-hydroxy ZnPcs might find application as photosensitizers in the PDT treatment of cancer.