Stable Organic Radical Cations in the Solid State

1. Stable Organic Radical Cations in the Solid State Monica Olvera, Northwestern University, DMR 0520513 Air-sensitive radical cations of the one-electron reduced bipyridinium dication (BIPY2+) have been stabilized in the solid state. We have harnessed the propensity of the cyclobis(paraquat-p-phenylene) ring, with its two BIPY2+ units, to serve as a host for methyl viologen, with one BIPY2+ unit, provided both host and guest exist as radical cations. The same interactions between radical species that drive the formation of inclusion complexes in solution also enable extended π-stacking (<3.3 Å interplanar distances) in the solid state, as evidenced by crystallographic data. These crystals hold considerable promise as potential conductive or semiconductive materials for nanoscale device applications. Future work involves collaboration with the Mirkin group toward constructing a nanoscale molecular electronic solid-state device. X-ray crystal structure of the BIPY•+  CBPQT2(+) host-guest complex. Into the plane of the screen: a display of continuous π-stacking in the solid state. NSF Grant #DMR-0520513 J. F. Stoddart et al., Nature Chem.2010, 2, 42‒49