ABSTRACT
Many molecules have been shown to be photodynamic sensitizers, including various acridines, porphyrins, phenothiazines, quinones, flavins, and metal derivatives such as ruthenium bipyridyl. An activated sensitizer can react directly with other molecules to produce free radicals by removal of an electron or of hydrogen, or the sensitizer can react with molecular oxygen in aqueous solution to produce activated forms of oxygen, particularly singlet oxygen. Another route to activated oxygen species lies in photoreduction of the molecule in the presence of a suitable hydrogen donor, followed by reaction of the reduced molecule (either one- or two-electron) with dioxygen with transfer of an electron to yield superoxide radical anions.
