Synthesis, structure, and one-electron redox reactions of 4,7-disubstituted benzotrichalcogenoles containing sulfur and/or selenium atoms

Stable 4,7-disubstituted benzotrichalcogenoles containing sulfur and/or selenium atoms in the five-membered ring were systematically and selectively prepared in good yields by reaction of the corresponding benzodichalcogenastannoles, a synthetic equivalent of benzenedichalcogenols, with an S1 or Se1 source. Characterization of these new trichalcogenole frameworks was performed by multi-nuclear NMR studies and X-ray crystallographic analyses. The cyclic voltammograms of the trichalcogenoles showed well-defined reversible electrochemical redox couples with low oxidation potential. Novel radical ions were isolated in quantitative yields in the one-electron oxidation of the trichalcogenoles with one equivalent of NOPF6 as a one-electron oxidant. The structures of the radical cation salts were analyzed by 31P-NMR and EPR spectroscopies, and elemental analyses. The salts underwent one-electron reduction on treatment with one equivalent of samarium(II) iodide to give the neutral starting trichalcogenoles quantitatively.