Syntheses and properties of a series of cationic water-soluble phthalocyanines

A series of symmetrical cationic phthalocyanines (Pcs) with either Zn(II) or Si(IV) metal ions and two bulky axial ligands on the silicon complexes was synthesized in high yields. The photophysical (absorption, emission, fluorescence, and singlet oxygen quantum yields) and cellular (uptake, toxicity, and subcellular localization) properties of this series of Pcs were investigated. The Si(IV) - Pcs exist mainly as monomers in aqueous media and have higher fluorescent quantum yields in protic solvents (methanol and water) than the Zn(II) - Pcs. The presence of eight short PEG groups at the periphery of a Zn(II) - Pc significantly increases its solubility in protic solvents, but a centrally chelated silicon ion and associated bulky axial ligands were more efficient in preventing aggregation of the Pc macrocycles. The singlet oxygen quantum yields for this series of Pcs in DMSO are in the range 0.09-0.15. All Pcs were readily taken up by human HEp2 cells, and the extent of their accumulation within cells depends on their hydrophobic character. Intracellularly, all Pcs localized preferentially within the cell lysosomes. The Zn(II) - Pc 11 and Si(IV) - Pcs 12 and 14 were found to be the most phototoxic (IC50 = 2.2 μM at a 1 J cm-2 light dose) of this series of compounds. © 2008 American Chemical Society