Persulfurated Benzene-Cored Asterisks with π-Extended ThioNaphthyl Arms: Synthesis, Structural, Photophysical and Covalent Dynamic Properties

The synthesis of regioisomeric asterisks (5) and (6) incorporating a benzene core with six 1-naphthylthio or six 2-naphthylthio arms are reported in search for new materials with optoelectronic properties. The consequences on the extension of a pi system surrounding a persulfurated benzene core provide a new avenue to study the structural, photophysical, and chemical properties of such family of all-organic phosphors. It also diverts the persulfuration mechanism after two radical cyclizations for making a [5]dithiohelicene by-product (7) and favors dynamic sulfur component exchange reactions surrounding the core. These exchanges convert asterisks (5) and (6), non-phosphorescent at 20 degrees C to the highly phosphorescent (4) (phi similar to 100 %, solid state at 20 degrees C). For asterisks (5) and (6), the absence of the typical phosphorescence of the per(phenylthio)benzene core in the solid state at 20 degrees C and the presence of a weak naphthalene-based phosphorescence at 77 K is attributed to an energy transfer from the triplet state of the persulfurated benzene core to the outer naphthalene moieties, resulting in an antenna system.