Thionation Induces Efficient Generation of Excited Triplet State and Singlet Oxygen: Heavy Atom-Free BODIPY Photosensitizers Based on S1(n,π*) State

The attachement of SR (R is alkyl or phenyl) makes BODIPY efficiently generate excited triplet state (T₁) and singlet oxygen with quantum yield up to 0.82 (compared to 0.10 of parent BODIPY). This affords an efficient method to synthesize heavy atom free photosensitizers. This efficient T₁ formation is because SR presence leads to a new excited state S₁(n,pi*) with an energy smaller but close to the usual S₁(pi,pi*) state.