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.