Chemistry

Radical Ring

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Science  06 Dec 2013:
Vol. 342, Issue 6163, pp. 1147
DOI: 10.1126/science.342.6163.1147-a
CREDIT: EIICHI KAYAHARA

Charge transport in conjugated π-bonded carbon frameworks is central to the operation of organic photovoltaic systems. Multiple studies have therefore probed the role of charge delocalization in facilitating this process. Kayahara et al. examined a simple model system, [8]cycloparaphenylene, in which eight phenyl rings are bound to one another at the para positions to form a loop. Applying one equivalent of nitrosyl hexafluoroantimonate as an oxidant stripped one electron from the compound, whereas five equivalents cleanly stripped two. Spectroscopic analyses by electron spin resonance (for the radical monocation) and nuclear magnetic resonance (for the dication) were consistent with complete spin and charge delocalization throughout the loop. Both salts were also relatively stable under a nitrogen atmosphere. The dication was characterized by x-ray crystallography and manifested a belt geometry, with a coplanar arrangement of all the constituent phenyl rings normal to the loop plane.

Angew. Chem. Int. Ed. 52, 10.1002/anie.201306881 (2013).

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