Dicationic Heteroacenes Containing Thio- or Selenopyrylium Moieties

Dicationic heteroacenes that bear thio- or selenopyrylium moieties were synthesized by addition reactions of the corresponding diones with a Grignard reagent, followed by a dehydration reaction of the resulting diols with Brønsted acid. Alternatively, these dicationic heteroacenes were obtained from two-electron oxidations of the corresponding sulfur- or selenium-containing quinoids. The electronic structures of these dicationic heteroacenes were examined by NMR and UV–vis–NIR spectroscopy in conjunction with density functional theory calculations. The results of this combined experimental and theoretical approach strongly imply effective conjugation of 22π-electrons in a system that is distributed over the entire pentacene framework