Site-selected thionated benzothioxanthene chromophores as heavy-atom-free small-molecule photosensitizers for photodynamic therapy

Site-selective thionation is a powerful strategy to access heavyatom-free small-molecule photosensitizers for photodynamic therapy. Here, a series of sulfur-substituted benzothioxanthene chromophores is synthesized and the sequential insertion of sulfur atoms is shown to result in strong and concomitant optimization of both light absorption and therapeutic activity.