Electrocatalytic Water Oxidation by a Monomeric Amidate-Ligated Fe(III)-Aqua Complex

The six-coordinate Fe-III-aqua complex [Fe-III(dpaq)(H2O)](2+) (1, dpaq is 2-[bis(pyridine-2-ylmethyl)]amino-N-quinolin-8-yl-acetamido) is an electrocatalyst for water oxidation in propylene carbonate-water mixtures. An electrochemical kinetics study has revealed that water oxidation occurs by oxidation to Fe-V(O)(2+) followed by a reaction first order in catalyst and added water, respectively, with k(o) = 0.035(4) M-1 s(-1) by the single-site mechanism found previously for Ru and Ir water oxidation catalysts. Sustained water oxidation catalysis occurs at a high surface area electrode to give O-2 through at least 29 turnovers over an 15 h electrolysis period with a 45% Faradaic yield and no observable decomposition of the catalyst.