Exploration of silicon phthalocyanines as viable photocatalysts for organic transformations

Abstract

Silicon phthalocyanines have been largely ignored as photocatalysts, despite their low energy excitation, long triplet lifetimes, and their ability to form singlet oxygen. By incorporating alkyl and silicon protecting groups as axial ligands on the silicon center, two silicon phthalocyanines have been generated with the goal of developing photocatalysts for organic synthesis. Using cyclic voltammetry and Stern Volmer quenching studies, we have shown silicon phthalocyanines are capable of electron transfer with appropriate substrates, including Hünig’s base. We have also successfully used these catalysts in a reductive quenching reaction where Hünig’s base served as a sacrificial electron donor in the reaction. In addition to being redox-active, our preliminary data also shows these compounds are capable of performing energy transfer reactions, by performing a reaction that utilizes singlet oxygen as a reactant under visible light conditions. This reaction, in combination with cyclic voltammetry studies, has also served as a model to understand how axial substitution on the silicon center seems to influence the photostability of these species.