From the Photosensitizer Hypericin to the Photoreceptor Stentorin— The Chemistry of Phenanthroperylene Quinones

Hypericin and stentorin are the most important representatives of the phenanthroperylene quinones. Their tautomerism, dissociation, conformation, and association equilibria make them structurally complex, and they are interesting on the one hand for medical applications (for example, photodynamic therapy) and on the other as biological photoreceptors.