Disaggregation of Zinc Tetra(4-Carboxyphenoxy) Phthalocyaninate in Aqueous Solutions of Dodecyl-, Tetradecyl-, and Hexadecyltrimethylammonium Bromides at pH 6–9

The aggregation of zinc tetra(4-carboxyphenoxy) phthalocyaninate, ZnPc(COOH) 4 , in organic solvents and water at different pH values has been analyzed using electronic absorption and luminescence spectroscopies. It has been found that, in aqueous systems at pH 6–9, ZnPc(COOH) 4 exists in an aggregated state, while it forms molecular solutions in dimethylformamide and dimethyl sulfoxide. The use of cationic surfactants (dodecyl-, tetradecyl-, and hexadecyltrimethylammonium bromides) causes the disaggregation of ZnPc(COOH) 4 into individual molecules in aqueous solutions at pH ≥ 6. This opens up possibilities of applying ZnPc(COOH) 4 as a preparation for photodynamic therapy in physiological solutions, because each molecule of this compound may participate in the generation of singlet molecular oxygen.