Reactive Channels

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Science  09 Jan 2009:
Vol. 323, Issue 5911, pp. 187
DOI: 10.1126/science.323.5911.187a

Coordination polymers consist of metal centers strung together by multiple ligands, often to form a porous framework material that can encapsulate molecular guests. For many coordination polymers, a change in the oxidation state of the metal leads to a collapse of the framework structure. One exception is a layered material based on [FeIII(CN)6]3− units, which is structurally stable to reduction because the reduced [FeII(CN)6]4− groups retain a similar coordination geometry. Yanai et al. have exploited this property by infiltrating the framework with pyrrole monomers, which are then oxidized and polymerized by the iron within well-defined channels. Addition of the chelator ethylenediamine tetraacetic acid cleanly dismantles the framework to liberate the polypyrrole. Whereas bulk polypyrrole has a granular morphology, the polypyrrole grown inside the coordination polymer (shown above) exhibited an overlapping plate structure made up of discernible stacks of thin layers. After the product was doped with iodine, the conductivity along the direction parallel to the plates was 20 times as high as that perpendicular to the plates, confirming the orienting impact of the iron host and catalyst framework. — MSL

Angew. Chem. Int. Ed. 47, 9883 (2008).

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