The oxidation of tetramethylphenylenediamine (TMPD) with (salen) CrVO+ generates initially the 2-electron product TMPD2+, followed by the reaction with excess TMPD to yield the radical cation, TMPD˙+. The kinetics of both TMPD/(salen) CrVO+ and TMPD/TMPD2+ reactions are acid-dependent, with TMPD being the most reactive form, and the doubly protonated TMPDH22+ exhibiting no discernible reactivity toward either (salen) CrVO+ or ...