Radical Cations and Radical Anions of Three Bridgehead Azopolycycloalkanes: A Fluid‐Solution ESR Study

The radical mono‐ions of three azoalkanes in which the azo group is connected to the polycyclic alkane moieties at the bridgehead C‐atoms, i. e . 1,1′‐azonorbornane ( 1 ), 1,1′‐azotwistane ( 2 ), and 1,1′‐azobi‐cyclo[3.2.1]octane ( 3 ), were studied in fluid solution by ESR spectroscopy. According to the ESR parameters and MO models, the radical cations of 1 – 3 should be considered as σ radicals, whereas the corresponding radical anions are π radicals. INDO calculations point to a remarkable dependence of the l4 N‐coupling constants on the geometry at the N‐atoms in the radical cations of aliphatic azo compounds.