Hard-Core Electrochemistry

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Science  06 Oct 2000:
Vol. 290, Issue 5489, pp. 13
DOI: 10.1126/science.290.5489.13d

The [4Fe-4S] clusters of ferrodoxin proteins can assume a wide range of oxidation states. Gorman and Smith have used these cube-like clusters as the core unit for polymer dendrimers, which are branched structures that increase in overall size with each succeeding round (or generation) of synthesis. They determined how the redox properties varied with generation number and found that this variation differed for molecules in solution versus those cast directly as films onto electrodes. The redox potentials in films shifted by half a volt as dendrimers grew from second- to fourth-generation, but the redox potential of solvated dendrimers did not change. Films exhibited similar overall electron transfer rates with increasing generation number, but rates in solution dropped two orders of magnitude between the second and fourth generation. The authors suggest that an electron-hopping mechanism functions efficiently in films in which the [4Fe-4S] clusters reside close to one another, but is not fast enough to operate in solvated dendrimers, which contact the electrode surface only transiently. — PDS

J. Am. Chem. Soc., 122, 9342 (2000).

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