Preparation, spectroscopic properties, and stability of water-soluble subphthalocyanines

A series of subphthalocyanines containing an axial pyridyl, amino, or carboxy group have been prepared. They undergo N-methylation or deprotonation readily to give a new series of water-soluble subphthalocyanines. All the compounds have been characterized with various spectroscopic methods and elemental analysis. The molecular structure of the amino analogue SPc(OCH(2)CH(2)NMe(2)) (6) has also been determined by X-ray diffraction analysis. All these compounds are essentially non-aggregated in DMF as shown by the strong Q-band absorption. The low aggregation tendency of these compounds also results in strong fluorescence emission and high efficiency in generating singlet oxygen. In the presence of Cremophor EL, these compounds also remain in the monomeric form in aqueous media and can sensitize the formation of singlet oxygen. The carboxy and carboxylate derivatives exhibit a relatively higher photostability than the amino and cationic pyridinium and ammonium counterparts, making them potentially useful as photosensitizers in aqueous media.