Lutetium(III) acetate phthalocyanines for photodynamic therapy applications: Synthesis and photophysicochemical properties

Abstract Background The development of new water-soluble photosensitizers for photodynamic therapy (PDT) applications is a very active research topic. Efforts have been made to obtain the far-red absorbing phthalocyanine complexes with molecular design that facilitates the uptake and selectivity for a high PDT efficiency. Methods The monomolecular lutetium(III) acetate phthalocyanines (LuPcs) substituted with methylpyridyloxy groups at non-peripheral ( 5 ) and peripheral ( 6 ) positions were synthesized by following the modification of the well-known synthetical routes. The photo-physicochemical properties of the both quaternized LuPcs were evaluated by the steady-state and time-resolved spectroscopy. The photochemical technique was applied to study the generation of the singlet oxygen. Results Two water-soluble and cationic LuPcs were synthesized and chemically characterized. The photo-physicochemical properties of absorption (675 and 685 nm) and the red shifted fluorescence (704 and 721 nm) as well as the fluorescence lifetimes (2.24 and 3.27 ns) were studied. The promising values of singlet oxygen quantum yields (0.32 for 5 and 0.35 for 6 ) were determined. Conclusions Lutetium(III) acetate phthalocyanine complexes were synthesized and evaluated with physicochemical properties suitable for future photodynamic therapy applications.