Iron redox couple electron-exchange

Control over electron transfer may also be obtained by clever selection of electroactive species. Facci and Murray incorporated both hexachloroiridate(III/IV) and hexacyanofer-rate(II/III) into copolymeric films containing protonated pyridyl groups ( ). The formal potential for the iridium couple is more positive than that for the iron couple. Therefore, Ir(IV) can mediate oxidation of Fe(II), and Fe(Il) can mediate reduction of Ir(lV). Facci and Murray observed that the cross-exchange contribution to electron transfer [eg. Ir(IV) + Fe(II) Ir(III) + Fe(III)] could be turned on and off by controlling the redox state of the iridium. Without the cross-exchange reaction, diffusional electron transport was the only mechanism available, and the rate of electron transfer was much slower. 

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