A Study on Ball-Types Phthalocyanines Substituted for Carboxyl Groups: Spectroscopic, Photophysical and Photochemical Properties

The synthesis of ball-type binuclear metal-free (H2BPc) and metallic (magnesium (MgBPc), cobalt (CoBPc), and zinc (ZnBPc)) phthalocyanine derivatives containing four benzoic acid substituents at the peripheral positions is described. The new compounds were fully characterized using elemental analysis, mass spectrometry, fourier-transform infrared, H-1 nuclear magnetic resonance and electronic spectroscopies. The Q band absorptions in DMSO were observed at 675/702 for H2BPc, at 668/698 for MgBPc, 672 nm for CoBPc and 681 nm for ZnBPc. Considering their potential application as photosensitisers in photodynamic therapy, the fluorescence quantum yield, triplet quantum yield, and singlet oxygen quantum yield of the diamagnetic derivatives was determined, and photodegredation quantum yields and magnetic circular dicroism measurements were performed for all complexes. The triplet lifetime value of the MgBPc was found to be larger than that of the metal-free and zinc counterparts, which were 60 mu s, 130 mu s and 60 mu s, respectively. H2BPc, MgBPc and ZnBPc were obtained singlet oxygen quantum yield of 0.03, 0.06 and 0.40 while the tiplet quantum yield were 0.84, 0.91 and 0.93 in DMSO, respectively.