Comparison of photophysicochemical properties of hexaphenoxycyclotriphosphazenyl-substituted metal-free, mono- and bis-lutetium phthalocyanines

Abstract

The aim of this study is to compare the photophysicochemical properties of hexaphenoxycyclotriphosphazenyl-substituted metal-free ( 1), mono-(phthalocyaninato) lutetium(III) ( 2) [Lu III(AcO)(Pc)] (Pc = phthalocyaninato, AcO = acetate) and bis-(phthalocyaninato) lutetium(III) ( 3) [Lu IIIPc 2]. The synthesis and characterization (using the elemental analysis, mass spectrometry, IR, 1H, and 31P NMR and UV–vis spectroscopy) of new compounds ( 2, 3) are described in this study. The electronic absorption and fluorescence spectral properties of compounds 1– 3 are investigated. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yields) measurements are also studied on hexaphenoxycyclotriphosphazenyl-appended metal-free, mono- and bis-lutetium phthalocyanines in dimethylsulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanines are very useful for photodynamic therapy (PDT) applications. Singlet oxygen quantum yields ( Φ Δ) give an indication of the potential of the complexes as photosensitizers in PDT applications. Hexaphenoxycyclotriphosphazenyl-substituted mono-(phthalocyaninato) lutetium(III) complex ( 2) gave good singlet oxygen quantum yield (0.66) in DMSO. Thus, this complex shows potential as Type II photosensitizer for PDT of cancer.