pi-conjugated benzoperylenes: Sequential C-S bond cleavage and charge distribution patterns of the anions

Chemical reduction of polyaromatic hydrocarbons yielded solutions of long-l ived polyanionic species. Reduction of a sulfur heterocycle afforded a stab le sulfur-containing dianion. Sulfur extrusion from this dianion proceeded upon further contact with the reducing metal. NMR and UV studies indicate a sulfur extrusion mechanism different than that previously observed in THF. Electron transfer to the already reduced hydrocarbon skeleton results in t he stepwise cleavage of the two C-S bonds and the extrusion of a sulfur ato m. Dimers of aromatic hydrocarbons such as pyrene and phenanthrene have bee n reduced as well. The interplay between coulombic repulsions and resonance energies is described.