Electrochemical metalloporphyrin-catalyzed reduction of chlorite.

We measured the redox stoichiometry and rate constants for the electrochemical reduction of ClO(2)(-) at pH 7, catalyzed by a series of metalloporphyrins of Mn, Fe, and Co with different proximal and distal environments. A clean four-electron reduction was observed. The catalytic activity correlates well with that observed in reduction of H(2)O(2). The axial imidazole and/or a redox-active distal metal (Cu or Co) increases the turnover frequency in several compounds. The metalloporphyrins were inert to ClO(x)(-) (x = 3,4) and IO(3)(-) but catalyzed facile two-electron reduction of IO(4)(-); six-electron reduction of BrO(3)(-) was also observed.