Electron Loss from 1,3,3-Trimethyl-2-azabicyclooctane Derivatives. Is ? Coupling Thermodynamically Important?

Article abstract of DOI:10.1021/jo00146a012

The ease of one-electron oxidation is compared for ? coupled and non-?-coupled γ-oxopiperidine nitroxides and their saturated analogues (CO -> CH2).For the non-?-coupled pair, 1,3,3-trimethyl-2-oxyl-2-azabicyclo<2.2.2>octan-5-one (9) has IP_v = 7.29 eV, E^o' = 0.73 V and its CO -> CH2 analogue 11 IP_v = 6.88, E^o' = 0.52 V.The ?-coupled pair 9-oxyl-9-azabicyclo<3.3.1>nonan-3-one (12) has IP_v = 7.78 eV, E^o' = 0.83 V and its CO -> CH2 analogue 13 IP_v = 7.39 eV, E^o' = 0.58 V.Replacement of CO by CH2 in the non-?-coupled example has as large an effectof IP_v and only a 13percent smaller effect on E^o' than in the ?-coupled example, making it appear that a ?-coupled transmission of positive charge from the nitrogen to the carbonyl in the radical cation is unimportant.