Kinetic effects in singlet oxygen mediated oxidations by immobilized photosensitizers on silica

Singlet oxygen (¹O₂) mediated photo-oxidations are important reactions involved in numerous processes in chemical and biological sciences. While most of the current research works have aimed at improving the efficiencies of these transformations either by increasing ¹O₂ quantum yields or by enhancing its lifetime, we establish herein that immobilization of a molecular photosensitizer onto silica surfaces affords significant, substrate dependant, enhancement in the reactivity of ¹O₂. Probing a classical model reaction (oxidation of Anthracene-9, 10-dipropionic acid, ADPA or dimethylanthracene, DMA) with various spectrofluorimetric techniques, it is here proposed that an interaction between polar substrates and the silica surface is responsible for the observed phenomenon. This discovery could have a direct impact on the design of future photosensitized ¹O₂ processes in various applications ranging from organic photochemistry to photobiology.