1981•Journal of the Chemical Society Perkin Transactions 2Requires access
The radical anion of [24](1,2,4,5)cyclophane
Fabian Gerson, Javier Lopez, Virgil Boekelheide
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Abstract
The radical anion of [24](1,2,4,5)cyclophane (I) has been investigated by e.s.r. and e.n.d.o.r. spectroscopy under a variety of conditions. In dimethylformamide (counterion Et4N+) and in 1,2-dimethoxyethane–hexamethylphosphoric triamide (3 : 1)(counterion K+) a ‘free’ or loosely associated radical anion (If–˙) is formed (effective symmetry D2h), whereas in tetrahydrofuran and 2-methyltetrahydrofuran (counterion K+ or Cs+) a tightly ion paired species (Ip–˙) is present (symmetry C2v; aKca. 0.1 or aCsca. 0.6–0.8 mT). In 1,2-dimethoxyethane (counterion K+), at low temperatures, (If–˙) and (Ip–˙) give rise concurrently to distinct e.s.r. and e.n.d.o.r. spectra; the inter-conversion (If˙+)+ K+⇌(Ip˙–)K+ must thus be slow on the hyperfine time-scale. The concentration ratio [(Ip–˙)]/[(If–˙)] in 1,2-dimethoxyethane is ca. 5 at 178 K and increases upon raising the temperature.