Highly photostable silicon(IV) phthalocyanines containing adamantane moieties: synthesis, structure, and properties

Two new axially disubstituted silicon(IV) phthalocyanines 1 and 2 have been synthesized by treating silicon phthalocyanine dichloride with 1-adamantanemethanol or 1-adamamtaneethanol, respectively. The crystal structure of compound 2 has been characterized by X-ray diffraction analysis. Both compounds are efficient singlet-oxygen generator with a quantum yield of 0.40–0.43. With two rigid bulky adamantane moieties at the axial positions, these phthalocyanines not only are essentially non-aggregated in common solvents, but also exhibit a high photostability. They are about 100 times more stable than zinc phthalocyanine under the same irradiation conditions. With the goal of enhancing the biocompatibilities, interactions and conjugations of these two compounds with bovine serum albumin have also been investigated.