Oxidation of halides by redox enhanced ferricyanide in the [Fe^II-CN-Pt^IV]_n coordination polymer: An optically triggered process

The mechanism of photolysis for a cyanometalate coordination polymer composed of [(NC)₅Fe^II-CN-Pt^IV(NH₃)₄]_n repeat units, is deduced based on the results of several photogalvanic techniques. These techniques are validated through characterization of the previously established photochemistry of [(NC)₅Fe^II-CN-Pt^IV(NH₃)₄-NC-Fe^II(CN)₅ ]^4-. Analysis of the polymer photoproducts indicates the presence of iron centers with a redox potential higher than that of the expected photoproduct, ferricyanide. Additionally, the charge collected at the electrode surface is greater than the number of iron centers freed from the polymer network by photolysis. A mechanism based on the creation of oxidized ferricyanide centers with multiple bridging cyanides is proposed. Each bridging cyanide to a Pt center increases the redox potential of the associated ferricyanide center. Ferricyanide centers with a sufficient number of bridging cyanides have redox potentials high enough to oxidize various halides to the corresponding halogen. The ability to convert chloride to chlorine suggests potential applications in the area of solar energy conversion.