A potentially general method for estimating the acidities of HA 2+ dications in DMSO solution based on a thermodynamic cycle has been developed by combination of the equilibrium acidity of the acid (PK HA ) with its oxidation potential [E ox (HA)], the oxidation potential of its conjugate base [E ox (A - )], and those of the corresponding radical [E ox (A . )] and radical cation [E ox (HA +. )] (eq 6). The pK HA+. values for the radical cations derived from 2,4,5-triphenylimidazole, p-(phenylamino)diphenylamine, and 5H-dibenz[bf]azepine (iminostilbene) by loss of an electron were found to be 1.5, 4.1, and 3.8, respectively, and the pK HA2+ values of the corresponding dications formed by loss of an electron from these radical cations were found to be -8. 1, -5.7, and -7.7, respectively