The preparation of, and electrochemical studies on, some substituted aryl dithiadiazolylium salts and dithiadiazolyl radicals

A series of aryl-substituted 1,2,3,5-dithiadiazolylium cations (I) and 1,3,2,4-dithiadiazolylium cations (II) were prepared as their hexafluoroarsenate(V) salts using standard methods. Electrochemical studies on I and II showed reversible one-electron reductions. The half-wave reduction potentials for a series of meta-substituted derivatives of both I and II exhibited a linear free energy relationship with the Hammett parameter, σ_m. The small value of the reaction constant, , for both meta and para-derivatives indicates that electronic effects are small and in the case of the ortho-derivatives of II, steric effects dominate the redox process. Reduction of the 1,2,3,5-dithiadiazolylium cations, as their chloride salts, yielded the corresponding dithiadiazolyl radicals (III).