“…In a similar fashion, the salts of radical cations of various polycyclic aromatic hydrocarbons, such as naphthalene, [37] biphenylene, [37b] anthracene, [37b,38] and fluorene, [39] were isolated as single crystals, and their X-ray structures determined. [37b] These studies were further extended to investigate the cationic systems of various sulfur-containing compounds such as thiophene, [40] 1,2- [41] and 1,4-dithiin, [42] and oligothiophenes [43] from the dimer to the octamer, all fully or partially annelated by BCO units. As expected, all of these compounds gave stable radical cations and dications.…”