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 hexaflu oroarsenate(V) salts using standard methods. Electrochemical studies o n I and II showed reversible one-electron reductions. The half-wave re duction potentials for a series of meta-substituted derivatives of bot h I and II exhibited a linear free energy relationship with the Hammet t parameter, sigma(m). The small value of the reaction constant, rho, for both meta and pala-derivatives indicates that electronic effects a re small and in the case of the ortho-derivatives of II, steric effect s dominate the redox process. Reduction of the 1,2,3,5-dithiadiazolyli um cations, as their chloride salts, yielded the corresponding dithiad iazolyl radicals (III). (C) 1997 Elsevier Science Ltd.