Design of Reversible One-electron Redox Systems Using Five-membered Heterocycles Containing Sulfur,Selenium,and Tellurium

摘要

Stable 4,7-disubstituted benzotrichalcogenoles containing sulfur,selenium,and tellurium atoms in the five-membered ring were systematically and selectively prepared in good yields by reaction of the corresponding benzodichalcogenastannoles or benzodichalcogenatitanoles,synthetic equivalents of benzenedichalcogenols,with an S_1 or Se_1 source.Characterization of these new trichalcogenole frameworks was performed by multi-nuclear ~119Sn,~77Se,~125Te 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 1 equiv.of NOPF_6 as a one-electron oxidant.The structures of the radical cation salts were analyzed by ~31P NMR and ESR spectroscopies,and elemental analyses.The salts underwent one-electron reduction on treatment with 1 equiv.of samarium (II) iodide to give the neutral starting trichalcogenoles quantitatively.