Design of reversible multi-electron redox systems using benzochalcogenophenes containing aryl and/or ferrocenyl fragments

2,3-Disubstituted benzo[b]thiophenes, 1,3-disubstituted benzo[c]thiophenes, and 1,3-disubstituted benzo[c]selenophene have been systematically and selectively synthesized from benzo[b]thiophene or phthaloyl dichloride as a starting material, respectively. Characterization of the molecules was performed by physical and spectroscopic means and X-ray crystallographic analyses. The cyclic voltammograms of the chalcogenophene derivatives containing aryl fragments showed well-defined reversible both anodic and cathodic steps derived from the unusually stable 5π chalcogenophene radical cations and 7π chalcogenophene radical anions. The cyclic voltammograms of the novel chalcogenophene derivatives containing ferrocenyl fragments showed a well-defined reversible cathodic step derived from the unusually stable 7π chalcogenophene radical anions and two distinct reversible anodic steps derived from ferrocenium cations separated from each other by a thiophene-heterocycle. The radical character of several novel 7π chalcogenophene radical anions was measured by ESR spectroscopy.